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Familial distal myopathy with rimmed vacuole and lamellar (myeloid) body formation
Abstract
Three cases from 2 families had muscle weakness with predilection for distal extremities, predominantly affecting the tibialis anterior muscles, and onset in early adulthood. The disorder seemed to be inherited through an autosomal recessive trait. The EMG demonstrated a myopathic pattern and CPK was mildly elevated. The striking finding in their muscle biopsies was the presence of "rimmed" vacuoles which had acid phosphatase-positive autophagic activity and which contained numerous concentric lamellar bodies in various forms (myeloid and cabbage bodies). Despite rapid clinical progression, not only necrotic fibers with phagocytosis, as seen in Duchenne dystrophy, but also evidence of regeneration were virtually absent. Continuous destruction of myofibrils by activation of certain lysosomal proteolytic enzymes might be responsible for the production of atrophic fibers.
... After an average of 12 to 15 years after disease onset, most of the patient dependent on a wheelchair [61,62]. Other hallmarks of GNEM are the finding of vacuoles in affected muscles [60,63], an onset in early adulthood [62,64], and a qu GNEM is a distal myopathy with a worldwide predicted prevalence of 1 to 9 patients per 1 million people [8] that first affects the tibialis anterior, the biceps femoris short head, and the adductor muscles [57,58] leading to certain gait problems and a typical foot-drop [59,60]. After an average of 12 to 15 years after disease onset, most of the patients will be dependent on a wheelchair [61,62]. ...
... After an average of 12 to 15 years after disease onset, most of the patients will be dependent on a wheelchair [61,62]. Other hallmarks of GNEM are the finding of rimmed vacuoles in affected muscles [60,63], an onset in early adulthood [62,64], and a quite slow progression of the disease [8,65]. GNEM-triggered inflammatory changes are not typical features of this disease [60,63,66], although there are confirmed exceptions to this statement [67][68][69]. ...
... Other hallmarks of GNEM are the finding of rimmed vacuoles in affected muscles [60,63], an onset in early adulthood [62,64], and a quite slow progression of the disease [8,65]. GNEM-triggered inflammatory changes are not typical features of this disease [60,63,66], although there are confirmed exceptions to this statement [67][68][69]. ...
Mutations in the gene coding for the bi-functional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), the key enzyme of the sialic acid biosynthesis, are responsible for autosomal-recessive GNE myopathy (GNEM). GNEM is an adult-onset disease with a yet unknown exact pathophysiology. Since the protein appears to work adequately for a certain period of time even though the mutation is already present, other effects appear to influence the onset and progression of the disease. In this study, we want to investigate whether the late onset of GNEM is based on an age-related effect, e.g., the accumulation of post-translational modifications (PTMs). Furthermore, we also want to investigate what effect on the enzyme activity such an accumulation would have. We will particularly focus on glycation, which is a PTM through non-enzymatic reactions between the carbonyl groups (e.g., of methylglyoxal (MGO) or glyoxal (GO)) with amino groups of proteins or other biomolecules. It is already known that the levels of both MGO and GO increase with age. For our investigations, we express each domain of the GNE separately, treat them with one of the glycation agents, and determine their activity. We demonstrate that the enzymatic activity of the N-acetylmannosamine kinase (GNE-kinase domain) decreases dramatically after glycation with MGO or GO—with a remaining activity of 13% ± 5% (5 mM MGO) and 22% ± 4% (5 mM GO). Whereas the activity of the UDP-N-acetylglucosamine 2-epimerase (GNE-epimerase domain) is only slightly reduced after glycation—with a remaining activity of 60% ± 8% (5 mM MGO) and 63% ± 5% (5 mM GO).
... GNE myopathy was initially reported by Nonaka et al. in Japan and Argov and Yarom in Israel. Nonaka et al. used the term distal myopathy with rimmed vacuoles (DMRV) to describe a familial myopathy with onset in early adulthood, predominantly affecting the anterior tibialis muscles, with mild serum creatine kinase (CK) elevation, and muscle histopathology characterized by fiber atrophy, rimmed vacuoles, lack of inflammation, and no evidence of regeneration [2,3]. Argov and Yarom described autosomal recessive inheritance of several Iranian Jewish families with a rimmed vacuole myopathy that spared the quadriceps [4]; Argov et al. later introduced the term Bhereditary inclusion body myopathy^(HIBM) to describe the disease [5]. ...
... Muscle biopsies of affected muscles show variation in muscle fiber size, atrophic fibers that are usually angular and clustered, the presence of characteristic Brimmedv acuoles, and typically lack of inflammation ( Fig. 4a-1) [2,4]. Modified Gomori trichome staining ( Fig. 4a-2) facilitates the identification of Brimmed vacuoles,^which may be missed with hematoxylin and eosin staining. ...
... (4) Electron microscopy of a rimmed vacuole containing cytoplasmic region, confirming that structures are indeed composed of autophagic vacuoles and myeloid bodies, in addition to excessive cellular debris. Scale bar in (1) represents 50 μm in section images shown in (1,2,3). Scale bar in (4) denotes 1 nm. ...
GNE myopathy, previously known as hereditary inclusion body myopathy (HIBM), or Nonaka myopathy, is a rare autosomal recessive muscle disease characterized by progressive skeletal muscle atrophy. It has an estimated prevalence of 1 to 9:1,000,000. GNE myopathy is caused by mutations in the GNE gene which encodes the rate-limiting enzyme of sialic acid biosynthesis. The pathophysiology of the disease is not entirely understood, but hyposialylation of muscle glycans is thought to play an essential role. The typical presentation is bilateral foot drop caused by weakness of the anterior tibialis muscles with onset in early adulthood. The disease slowly progresses over the next decades to involve skeletal muscles throughout the body, with relative sparing of the quadriceps until late stages of the disease. The diagnosis of GNE myopathy should be considered in young adults presenting with bilateral foot drop. Histopathologic findings on muscle biopsies include fiber size variation, atrophic fibers, lack of inflammation, and the characteristic “rimmed” vacuoles on modified Gomori trichome staining. The diagnosis is confirmed by the presence of pathogenic (mostly missense) mutations in both alleles of the GNE gene. Although there is no approved therapy for this disease, preclinical and clinical studies of several potential therapies are underway, including substrate replacement and gene therapy-based strategies. However, developing therapies for GNE myopathy is complicated by several factors, including the rare incidence of disease, limited preclinical models, lack of reliable biomarkers, and slow disease progression.
... Known by many different names ("Nonaka distal myopathy, " "distal myopathy with rimmed vacuoles, " "hereditary inclusion body myositis, " "quadriceps-sparing myopathy, " among others), this condition results in progressive muscle weakness resulting from changes in the bifunctional enzyme UDP-N-acetylglucosamine (GlcNAc) 2-epimerase/Nacetylmannosamine (ManNAc) kinase. This disorder was first described in the early 1980s by Nonaka et al. in Japan, but since then has been seen throughout the world, often in clusters (1). GNE myopathy is rare, though recent evidence suggests that the disorder may be more prevalent than previously thought (2). ...
... In 1981, Ikuya Nonaka et al. described three cases from two families with distal weakness "predominantly affecting the tibialis anterior muscles, " and muscle biopsy showing rimmed vacuoles containing "numerous concentric lamellar bodies" (1). In 1984, Zohar Argov described nine cases among four Iranian-Jewish families presenting with generalized weakness, where the "quadriceps muscle was the only leg muscle which retained its normal power" (8). ...
GNE myopathy is an ultrarare muscle disease characterized by slowly progressive muscle weakness. Symptoms typically start in early adulthood, with weakness and atrophy in the tibialis anterior muscles and with slow progression over time, which largely spares the quadriceps muscles. Muscle biopsy shows atrophic fibers and rimmed vacuoles without inflammation. Inherited in an autosomal recessive manner, patients with GNE myopathy carry mutations in the GNE gene which affect the sialic acid synthesis pathway. Here, we look at the history and clinical aspects of GNE myopathy, as well as focus on prior treatment trials and challenges and unmet needs related to this disorder.
... The worldwide prevalence of GNEM is reported to be 4-21 patients per million of population [2,3]. GNE myopathy was first described as familial inheritance myopathy by Nonaka et al. in 1981 characterized by rimmed vacuole formation in anterior tibialis muscle biopsy with no inflammation and muscle atrophy [4]. Similar reports from Argov were observed in Iranian Jewish patients with inherited autosomal recessive nature of GNE mutations and formation of rimmed vacuoles in anterior tibialis muscle sparing quadriceps (defined as quadricep sparing myopathy, QSM) [5,6]. ...
... The worldwide prevalence of GNEM is reported to be 4-21 patients per million of population [2,3]. GNE myopathy was first described as familial inheritance myopathy by Nonaka et al. in 1981 characterized by rimmed vacuole formation in anterior tibialis muscle biopsy with no inflammation and muscle atrophy [4]. Similar reports from Argov were observed in Iranian Jewish patients with inherited autosomal recessive nature of GNE mutations and formation of rimmed vacuoles in anterior tibialis muscle sparing quadriceps (defined as quadricep sparing myopathy, QSM) [5,6]. ...
UDP-N-Acetyl glucosamine-2 epimerase/N-acetyl mannosamine kinase (GNE) catalyzes key enzymatic reactions in the biosynthesis of sialic acid. Mutation in GNE gene causes GNE myopathy (GNEM) characterized by adult-onset muscle weakness and degeneration. However, recent studies propose alternate roles of GNE in other cellular processes beside sialic acid biosynthesis, particularly interaction of GNE with α-actinin 1 and 2. Lack of appropriate model system limits drug and treatment options for GNEM as GNE knockout was found to be embryonically lethal. In the present study, we have generated L6 rat skeletal muscle myoblast cell-based model system carrying one single Gne allele where GNE gene is knocked out at exon-3 using AAV mediated SEPT homology recombination (SKM-GNEHz). The cell line was heterozygous for GNE gene with one wild type and one truncated allele as confirmed by sequencing. The phenotype showed reduced GNE epimerase activity with little reduction in sialic acid content. In addition, the heterozygous GNE knockout cells revealed altered cytoskeletal organization with disrupted actin filament. Further, we observed increased levels of RhoA leading to reduced cofilin activity and causing reduced F-actin polymerization. The disturbed signaling cascade resulted in reduced migration of SKM-GNEHz cells. Our study indicates possible role of GNE in regulating actin dynamics and cell migration of skeletal muscle cell. The skeletal muscle cell-based system offers great potential in understanding pathomechanism and target identification for GNEM.
... Hereditary inclusion body myopathy (HIBM) refers to a rare heterogeneous group of neuromuscular diseases with autosomal recessive or dominant inheritance, which is characterized by muscle fibers containing rimmed vacuoles and inclusions consisting of tubulofilaments with a diameter of 15-21 nm Engel, 1993, 1998;Broccolini and Mirabella, 2015). The most common form of HIBM, also known as GNE myopathy, is autosomal recessive (Nonaka et al., 1981;Nishino et al., 2002), and the other identified forms of HIBM are autosomal dominant. This disorder of GNE myopathy is mainly due to the UDP-Nacetylglucosamine 2-epimerase/Nacetylmannosamine kinase (GNE) gene mutations, leading to abnormal sialylation of glycoproteins and relentless muscle degeneration (Argov and Yarom, 1984;Eisenberg et al., 2001). ...
... There are mainly five different HIBMs, such as HIBM1, HIBM2, HIBM-PFD, HIBM-ERF, and HIBM3. Numerous studies have been performed and a few causal mutations had been reported (Nonaka et al., 1981;Horowitz and Schmalbruch, 1994;Darin et al., 1998;Goldfarb et al., 1998;Martinsson et al., 1999Martinsson et al., , 2000Saavedra-Matiz et al., 2000;Nishino et al., 2002). Besides, our previous study described a new subtype of HIBM named as HIBM4. ...
Hereditary Inclusion Body Myopathy (HIBM) is a rare autosomal dominant or recessive adult onset muscle disease which affects one to three individuals per million worldwide. This disease is autosomal dominant or recessive and occurs in adulthood. Our previous study reported a new subtype of HIBM linked to the susceptibility locus at 7q22.1-31.1. The present study is aimed to identify the candidate gene responsible for the phenotype in HIBM pedigree. After multipoint linkage analysis, we performed targeted capture sequencing on 16 members and whole-exome sequencing (WES) on 5 members. Bioinformatics filtering was performed to prioritize the candidate pathogenic gene variants, which were further genotyped by Sanger sequencing. Our results showed that the highest peak of LOD score (4.70) was on chromosome 7q22.1-31.1.We identified 2 and 22 candidates using targeted capture sequencing and WES respectively, only one of which as CFTRc.1666A>G mutation was well cosegregated with the HIBM phenotype. Using transcriptome analysis, we did not detect the differences of CFTR's mRNA expression in the proband compared with healthy members. Due to low incidence of HIBM and there is no other pedigree to assess, mutation was detected in three patients with duchenne muscular dystrophyn (DMD) and five patients with limb-girdle muscular dystrophy (LGMD). And we found that the frequency of mutation detected in DMD and LGMD patients was higher than that of being expected in normal population. We suggested that the CFTRc.1666A>G may be a candidate marker which has strong genetic linkage with the causative gene in the HIBM family.
... This review compiles current literature on one of the many rare inherited neuromuscular diseases, GNE myopathy (GNEM), which is caused due to biallelic mutations in the GNE gene. Earlier studies described GNE myopathy as Nonaka distal myopathy, later known as distal myopathy with rimmed vacuoles in Japanese patients (Nonaka et al. 1981). In Iranian-Jewish patients, this disorder was named inclusion body myopathy (IBM2) or hereditary inclusion body myopathy (HIBM) (Argov and Yarom 1984;Argov et al. 2003). ...
GNE myopathy is a rare genetic neuromuscular disease that is caused due to mutations in the GNE gene responsible for sialic acid biosynthesis. Foot drop is the most common initial symptom observed in GNE myopathy patients. There is slow progressive muscle weakness in the lower and upper extremities while the quadriceps muscles are usually spared. The exact pathophysiology of the disease is unknown. Besides sialic acid biosynthesis, recent studies suggest either direct or indirect involvement of GNE in other cellular functions such as protein aggregation, apoptosis, ER stress, cell migration, HSP70 chaperone activity, autophagy, muscle atrophy, and myogenesis. Both animal and in vitro cell-based model systems are generated to elucidate the mechanism of GNE myopathy and evaluate the efficacy of therapies. The many therapeutic avenues explored include supplementation with sialic acid derivatives or precursors and gene therapy. Recent studies suggest other therapeutic options such as modulators of HSP70 chaperone (BGP-15), cofilin activator (CGA), and ligands like IGF-1 that may help to rescue cellular defects due to GNE dysfunction. This review provides an overview of the pathophysiology associated with GNE function in the cell and promising therapeutic leads to be explored for future drug development.
... Manifestation of the disease usually starts during early adulthood, and patients are mostly wheelchair dependent 10 to 15 years after the onset of the disease (Pogoryelova et al. 2018). Pathohistological findings show characteristic rimmed vacuoles containing protein aggregates, among which amyloid β and hyperphosphorylated tau have been identified (Nonaka et al. 1981;Argov and Yarom 1984;Carrillo et al. 2018;Devi et al. 2018). Although not a criterion for GNEM, inflammation occurs in some patients, especially in the early stages (Krause et al. 2003;Yabe et al. 2003). ...
GNE myopathy (GNEM) is a late-onset muscle atrophy, caused by mutations in the gene for the key enzyme of sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE). With an incidence of one to nine cases per million it is an ultra-rare, so far untreatable, autosomal recessive disease. Several attempts have been made to treat GNEM patients by oral supplementation with sialic acid precursors (e.g. N-acetylmannosamine, ManNAc) to restore sarcolemmal sialylation and muscle strength. In most studies, however, no significant improvement was observed. The lack of a suitable mouse model makes it difficult to understand the exact pathomechanism of GNEM and many years of research have failed to identify the role of GNE in skeletal muscle due to the lack of appropriate tools. We established a CRISPR/Cas9-mediated Gne-knockout cell line using murine C2C12 cells to gain insight into the actual role of the GNE enzyme and sialylation in a muscular context. The main aspect of this study was to evaluate the therapeutic potential of ManNAc and N-acetylneuraminic acid (Neu5Ac). Treatment of Gne-deficient C2C12 cells with Neu5Ac, but not with ManNAc, showed a restoration of the sialylation level back to wild type levels–albeit only with long-term treatment, which could explain the rather low therapeutic potential. We furthermore highlight the importance of sialic acids on myogenesis, for C2C12 Gne-knockout myoblasts lack the ability to differentiate into mature myotubes.
... First described in 1981 [1], GNE myopathy is a rare neuromuscular disease (GNEM; OMIM: 605820) with an estimated prevalence of one to nine per million [2]. The cellular phenotype of this disease is characterized by the formation of rimmed vacuoles and protein aggregates in muscle cells, followed by loss of affected muscle cells [2,3]. ...
Background:
A key mechanism in the neuromuscular disease GNE myopathy (GNEM) is believed to be that point mutations in the GNE gene impair sialic acid synthesis - maybe due to UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) activity restrictions - and resulting in muscle tissue loss. N-acetylmannosamine (ManNAc) is the first product of the bifunctional GNE enzyme and can therefore be regarded as a precursor of sialic acids. This study investigates whether this is also a suitable substance for restoring the sialic acid content in GNE-deficient cells.
Methods:
A HEK-293 GNE-knockout cell line was generated using CRISPR-Cas9 and analyzed for its ability to synthesize sialic acids. The cells were then supplemented with ManNAc to compensate for possible GNE inactivity and thereby restore sialic acid synthesis. Sialic acid levels were monitored by immunoblot and high performance liquid chromatography (HPLC).
Results:
The HEK-293 GNE-knockout cells showed almost no polysialylation signal (immunoblot) and a reduced overall (-71%) N-acetylneuraminic acid (Neu5Ac) level (HPLC) relative to total protein and normalized to wild type level. Supplementation of GNE-deficient HEK-293 cells with 2 mM ManNAc can restore polysialylation and free intracellular sialic acid levels to wild type levels. The addition of 1 mM ManNAc is sufficient to restore the membrane-bound sialic acid level.
Conclusions:
Although the mechanism behind this needs further investigation and although it remains unclear why adding ManNAc to GNE-deficient cells is sufficient to elevate polysialylation back to wild type levels - since this substance is also converted by the GNE, all of this might yet prove helpful in the development of an appropriate therapy for GNEM.
... GNE myopathy (also known as distal myopathy with rimmed vacuoles [DMRV], hereditary inclusion body myopathy [hIBM] or Nonaka Disease) is a hereditary myogenic disorder that results in muscle weakness due to a defect in muscle itself [1][2][3][4][5][6]. Although most myogenic disorders present with involvement of muscles in the trunk (around chest and hip) as well as upper arms and the proximal lower limbs, distal myopathies characteristically show gradually progressing weakness of muscles starting in the distal parts of the legs, particularly muscles such as tibialis anterior, with sparing of the quadriceps. ...
Background
A rare muscle disease, GNE myopathy is caused by mutations in the GNE gene involved in sialic acid biosynthesis. Our recent phase II/III study has indicated that oral administration of aceneuramic acid to patients slows disease progression.
Methods
We conducted a phase III, randomized, placebo-controlled, double-blind, parallel-group, multicenter study. Participants were assigned to receive an extended-release formulation of aceneuramic acid (SA-ER) or placebo. Changes in muscle strength and function over 48 weeks were compared between treatment groups using change in the upper extremity composite (UEC) score from baseline to Week 48 as the primary endpoint and the investigator-assessed efficacy rate as the key secondary endpoint. For safety, adverse events, vital signs, body weight, electrocardiogram, and clinical laboratory results were monitored.
Results
A total of 14 patients were enrolled and given SA-ER (n = 10) or placebo (n = 4) tablets orally. Decrease in least square mean (LSM) change in UEC score at Week 48 with SA-ER (− 0.115 kg) was numerically smaller as compared with placebo (− 2.625 kg), with LSM difference (95% confidence interval) of 2.510 (− 1.720 to 6.740) kg. In addition, efficacy was higher with SA-ER as compared with placebo. No clinically significant adverse events or other safety concerns were observed.
Conclusions
The present study reproducibly showed a trend towards slowing of loss of muscle strength and function with orally administered SA-ER, indicating supplementation with sialic acid might be a promising replacement therapy for GNE myopathy.
Trial registration number : ClinicalTrials.gov (NCT04671472).
... GNE myopathy (also known as distal myopathy with rimmed vacuoles, hereditary inclusion body myopathy, or Nonaka disease) is a hereditary muscle disorder characterized by a decrease in muscle strength, especially in distal muscles [1][2][3][4][5][6]. Particularly, tibialis anterior muscles are affected early at the onset of this disease, resulting in a gradually progressive decrease in muscle strength in the four limbs. ...
Background:
GNE myopathy is an ultra-rare muscle disease characterized by a reduction in the synthesis of sialic acid derived from pathogenic variants in the GNE gene. No treatment has been established so far.
Objective:
We evaluated the safety and efficacy of oral supplementation of aceneuramic acid in patients with GNE myopathy.
Methods:
This multicenter, placebo-controlled, double-blind study comprised genetically confirmed GNE myopathy patients in Japan who were randomly assigned into treatment groups of sialic acid-extended release (SA-ER) tablets (6 g/day for 48 weeks) or placebo groups (4:1). The primary endpoint of effectiveness was set as the change in total upper limb muscle strength (upper extremity composite [UEC] score) from the start of administration to the final evaluation time point.
Results:
Among the 20 enrolled patients (SA-ER group, 16; placebo group, 4), 19 completed this 48-week study. The mean value of change in UEC score (95% confidence interval [CI]) at 48 weeks was -0.1 kg (-2.1 to 2.0) in the SA-ER group and -5.1 kg (-10.4 to 0.3) in the placebo group. The least squares mean difference (95% CI) between the groups in the covariance analysis was 4.8 kg (-0.3 to 9.9; P = 0.0635). The change in UEC score at 48 weeks was significantly higher in the SA-ER group compared with the placebo group (P = 0.0013) in the generalized estimating equation test repeated measurement analysis. In one patient in the SA-ER group, who was found to be pregnant 2 weeks after drug administration fetal death with tangled umbilical cord occurred at 13 weeks after the discontinuation of treatment. No other serious adverse effects were observed.
Conclusions:
The present study indicates that oral administration of SA-ER tablets is effective and safe in patients with GNE myopathy in Japan.
... More recently, biallelic pathogenic variants in this gene have been shown to be associated with autosomal recessive GNE myopathy, known by multiple names including inclusion body myopathy À2, distal myopathy with or without rimmed vacuoles or Nonaka myopathy. 10,11 These myopathies are clinically characterized by slowly progressive distal muscle weakness with onset in the late teens to early adult years, most beginning after age 20, with features of foot drop and slowly progressive proximal muscle weakness. A unique feature of this condition is sparing of the quadriceps muscle, even in advanced stages of the disease. ...
Background:
The inherited macrothrombocytopenias are rare disorders and the underlying cause can be identified in many cases but in some, this can remain enigmatic. Platelet transfusions are often administered during hemorrhagic events.
Methods:
A patient with previously unexplained inherited macrothrombocytopenia with a platelet count between 3-20 × 109 /L is described in which studies were performed using exome sequencing (ES) and platelet flow cytometry.
Results:
Both the hemoglobin and white cell counts were normal. ES revealed two suspicious variants, one likely pathogenic and one a variant of uncertain significance, in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, and flow cytometry showed diminished expression of surface platelet sialic acid (about 5%) but normal red cell sialic acid. The Thrombopoietin (TPO) level was low, and the patient responded to TPO-mimetic treatment with an increase in the platelet count.
Conclusion:
Two variants in the GNE gene were able to be upgraded to pathogenic with apparently restricted expression to the megakaryocyte lineage. Platelet transfusion may be avoided in these patients with TPO-mimetic treatment.
... GNE myopathy (GNEM) was first described independently by Nonaka in 1981 as distal myopathy with rimmed vacuoles [1] and by Argov and Yarom in 1984 as rimmed vacuole myopathy sparing the quadriceps [2]. ...
GNE myopathy (GNEM) is a rare hereditary disease, but at the same time, it is the most common distal myopathy in several countries due to a founder effect of some pathogenic variants in the GNE gene. We collected the largest cohort of patients with GNEM from Russia and analyzed their mutational spectrum and clinical data. In our cohort, 10 novel variants were found, including 2 frameshift variants and 2 large deletions. One novel missense variant c.169_170delGCinsTT (p.(Ala57Phe)) was detected in 4 families in a homozygous state and in 3 unrelated patients in a compound heterozygous state. It was the second most frequent variant in our cohort. All families with this novel frequent variant were non-consanguineous and originated from the 3 neighboring areas in the European part of Russia. The clinical picture of the patients carrying this novel variant was typical, but the severity of clinical manifestation differed significantly. In our study, we reported two atypical cases expanding the phenotypic spectrum of GNEM. One female patient had severe quadriceps atrophy, hand joint contractures, keloid scars, and non-classical pattern on leg muscle magnetic resonance imaging, which was more similar to atypical collagenopathy rather than GNEM. Another patient initially had been observed with spinal muscular atrophy due to asymmetric atrophy of hand muscles and results of electromyography. The peculiar pattern of muscle involvement on magnetic resonance imaging consisted of pronounced changes in the posterior thigh muscle group with relatively spared muscles of the lower legs, apart from the soleus muscles. Different variants in the GNE gene were found in both atypical cases. Thus, our data expand the mutational and clinical spectrum of GNEM.
... Some communities, such as the Persian Jewish community, have a much higher prevalence of~1/1500 2 . Historically, prior to the identification of the underlying genetic defect, GNE myopathy was independently described by various investigators as Nonaka distal myopathy, distal myopathy with rimmed vacuoles, vacuolar myopathy sparing quadriceps, and inclusion body myopathy 2 (IBM2) [3][4][5][6] . On a molecular level, the GNE gene encodes a protein containing two enzymatic domains, the epimerase, and kinase domain, which are involved in sequential steps of the biosynthesis of sialic acid. ...
Hereditary muscle diseases are disabling disorders lacking effective treatments. UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) myopathy (GNEM) is an autosomal recessive distal myopathy with rimmed vacuoles typically manifesting in late adolescence/early adulthood. GNE encodes the rate-limiting enzyme in sialic acid biosynthesis, which is necessary for the proper function of numerous biological processes. Outside of the causative gene, very little is known about the mechanisms contributing to the development of GNE myopathy. In the present study, we aimed to address this knowledge gap by querying the underlying mechanisms of GNE myopathy using a patient-derived induced pluripotent stem-cell (iPSC) model. Control and patient-specific iPSCs were differentiated down a skeletal muscle lineage, whereby patient-derived GNEM iPSC clones were able to recapitulate key characteristics of the human pathology and further demonstrated defects in myogenic progression. Single-cell RNA sequencing time course studies revealed clear differences between control and GNEM iPSC-derived muscle precursor cells (iMPCs), while pathway studies implicated altered stress and autophagy signaling in GNEM iMPCs. Treatment of GNEM patient-derived iMPCs with an autophagy activator improved myogenic differentiation. In summary, we report an in vitro, iPSC-based model of GNE myopathy and implicate defective myogenesis as a contributing mechanism to the etiology of GNE myopathy.
... The same GNE gene is involved in causing Nonaka myopathy (NK; MIM:605820) as well, besides sialuria and sialdoses. In Nonaka myopathy, muscle wasting and weakness of the distal and anterior tibial muscles takes place 23,24 . Several mutations in the GNE gene in epimerase and kinases domains alter the enzymatic activity in a very minute and precise way. ...
Background: Single nucleotide polymorphism/mutation in the R263L region of the allosteric site of the GNE gene produces a phenotype with an overproduction of intracellular levels of sialic acid and causes sialuria. In sialuria, a defective GNE gene, synthesized with lost feedback inhibition mechanism, produces many developmental delays and varying degrees of intellectual disabilities in children and adolescents. Several mutations in the epimerase and kinase domains exist that cause difficulty in getting a precise and exact effect of the GNE gene on the disease severity and sialic acid levels. This is the first study investigating the molecular basis of neuronal disorders exhibiting sialuria in Pakistani children/ adolescents.
Methodology: The current study quantified the mRNA expression of the GNE gene and urinary sialic acid concentration by Realtime-qRT-PCR and Fluorimetric assays, respectively. The correlation between relative mRNA and urinary sialic acid levels was evaluated by using Pearson Bivariate correlations.
Results: The data show that severely intellectually disabled (I.D.) patients showed significantly reduced mRNA expression levels of the GNE gene compared to controls. The concentrations of free sialic acid in urine were significantly reduced in severe I.D. patients compared to controls. Whereas patients with mild I.D. showed a two-fold increase in sialic acid levels when compared to controls. A significant correlation was found between an increased GNE mRNA and low urinary sialic acid levels from severe I.D. patients.
Conclusion: The effect of the GNE gene is beyond hyposialylation that could hinder N-glycan structure and sialic acid biosynthesis. The study highlighted the possible involvement of sialic acid levels with different degrees of intellectual disabilities in Pakistani children and adolescents.
... Hereditary inclusion body myopathy (HIBM), also known as Nonaka myopathy or GNE myopathy, is rare autosomal recessive disease caused by defects in muscles leading to progressive skeletal muscle atrophy. It was initially reported by Nonaka et al. in Japan and Argov and Yarom in Israel [1][2][3]. HIBM starts in the stage of young adulthood, with the most common symptoms arising in the second and third decades. The first sign of this myopathy may include features like weakness in distal limb muscles. ...
GNE gene-specific c.2179G>A(p.V727M) is a key alteration reported in patients with hereditary inclusion body myopathy (HIBM) and represents an ethnic founder mutation in the Indian cohort. However, the underlying role of this mutation in pathogenesis remains largely unknown. Thus, in this study, we aimed to access possible mechanisms of V727M mutation that could be leading to myopathy. We evaluated various in silico tools to predict the effect of this mutation on pathogenicity, structural or possible interactions, that could induce myopathy. Our results propose that V727M mutation could induce deleterious effects or pathogenicity and affect the stability of GNE protein. Analysis of differential genes reported in the V727 mutant case suggests that it can affect GNE protein interaction with Myc-proto-oncogene (MYC) transcription factor. Our in silico analysis also suggests a possible interaction between GNE ManNac-kinase domain with MYC protein at the C-terminal DNA-binding domain. MYC targets reported in skeletal muscles via ChIP-seq suggest that it plays a key role in regulating the expression of many genes reported differentially expressed in V727M-mutated HIBMs. We conclude that V727M mutation could alter the interaction of GNE with MYC thereby altering transcription of sialyltransferase and neuromuscular genes, thus understanding these effects could pave the way for developing effective therapies against HIBM.
... Independently described by Nonaka et al. and by Argov and Yarom, the GNE distal myopathy is a rimmed vacuolar recessive myopathy with an early adult onset 153,154 . It first affects the anterior compartment of lower legs and thigh hamstring muscles with sparing of the quadriceps, but the progression is rather severe, and half of the patients loose ambulation within 10 years. ...
Distal myopathies are genetic primary muscle disorders with a prominent weakness at onset in hands and/or feet. The age of onset (from early childhood to adulthood), the distribution of muscle weakness (upper versus lower limbs) and the histological findings (ranging from nonspecific myopathic changes to myofibrillar disarrays and rimmed vacuoles) are extremely variable. However, despite being characterized by a wide clinical and genetic heterogeneity, the distal myopathies are a category of muscular dystrophies: genetic diseases with progressive loss of muscle fibers. Myopathic congenital arthrogryposis is also a form of distal myopathy usually caused by focal amyoplasia.
Massive parallel sequencing has further expanded the long list of genes associated with a distal myopathy, and contributed identifying as distal myopathy-causative rare variants in genes more often related with other skeletal or cardiac muscle diseases.
Currently, almost 20 genes (ACTN2, CAV3, CRYAB, DNAJB6, DNM2, FLNC, HNRNPA1, HSPB8, KHLH9, LDB3, MATR3, MB, MYOT, PLIN4, TIA1, VCP, NOTCH2NLC, LRP12, GIPS1) have been associated with an autosomal dominant form of distal myopathy. Pathogenic changes in four genes (ADSSL, ANO5, DYSF, GNE) cause an autosomal recessive form; and disease-causing variants in five genes (DES, MYH7, NEB, RYR1 and TTN) result either in a dominant or in a recessive distal myopathy. Finally, a digenic mechanism, underlying a Welander-like form of distal myopathy, has been recently elucidated. Rare pathogenic mutations in SQSTM1, previously identified with a bone disease (Paget disease), unexpectedly cause a distal myopathy when combined with a common polymorphism in TIA1.
The present review aims at describing the genetic basis of distal myopathy and at summarizing the clinical features of the different forms described so far.
... Enzyme activity is a limiting factor in sialic acid synthesis. It is known that a missense mutation of GNE gene can result in hereditary skeletal muscle atrophy or distal myopathy with rimmed vacuoles (DMRV) [4][5][6]. ...
Objective:
We generated induced pluripotent stem (iPS) cells from a patient with distal myopathy with rimmed vacuoles (DMRV), in which sialic acids synthesis is reported to be defective. In this study, we examined whether the differentiation to retinal pigment epithelial (RPE) cells and autophagy was affected in the patient derived cells.
Methods:
Patient derived iPS cells were established through the transduction of re-programming factors into peripheral mononuclear cells via retrovirus vectors. RPE cells were induced from iPS cells through aggregation culture. Then the autophagy induced by amino acid starvation was estimated by measuring LC3-containing "puncta" structure.
Results:
A 3D aggregate culture of patient-derived iPS cells resulted in some irregular shapes, and the aggregate contained large vacuoles filled with lipid droplets and cellular components such as damaged mitochondria. RPE cells induced from patient-derived iPS cells showed impaired autophagy flux under amino acid starvation.
Conclusion:
These findings were similar to those of sialidosis patient-derived iPS cells, in which cleavage of terminal sialic acids in oligosaccharide chains is defective. This suggests that the control of both the addition and removal of sialic acids are pivotal for autophagy progression.
... INTRODUCTION UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) myopathy (GNEM) is characterized clinically by distal dominant muscle atrophy and weakness and pathologically by rimmed vacuoles (RVs), which are accumulations of autophagic vacuoles and various proteins. 1,2 The causative gene is GNE, which encodes the bifunctional enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE/MNK). 3,4 This cytosolic enzyme is essential for sialic acid biosynthesis, 5,6 and GNE/MNK enzymatic activities are reduced to 70-90% in cells transfected with mutant GNE. ...
UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) is necessary for sialic acid biosynthesis. GNE myopathy is caused by a defect in GNE, and hyposialylation is a key factor in the pathomechanism of GNE myopathy. Although candidates for evaluating hyposialylation have been reported, it is difficult to measure them in routine clinical practice. Sialylation is necessary for synthesis of various glyco- proteins, including Krebs von den Lungen-6 (KL-6)/mucin 1 (MUC1). Here we report that KL-6/MUC1 is decreased in GNE myopathy. We observed that KL-6 levels were decreased in the serum of patients with GNE myopathy, and that KL-6 and MUC1-C were also decreased in muscle biopsy specimens from these patients. An immunofluorescent study revealed that KL-6 and MUC1-C were not present in the sar- colemma but were, instead, localized in rimmed vacuoles in specimens from patients with GNE myopathy. KL-6 is already used to detect lung diseases in clinical practice, and this glyco- protein may be a novel candidate for evaluating hyposialylation in GNE myopathy.
... GNE, or bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, myopathy is also known as a distal myopathy with rimmed vacuoles, quadriceps-sparing myopathy, and hereditary inclusion body myopathy. [1][2][3] It took 33 years to identify that the same clinical symptoms manifest in all these diseases caused by GNE mutations, and thus, they are the same disease. 4 Clinical presentation first starts with foot drop, followed by lower and upper extremity muscle weaknesses but sparing the quadriceps force. ...
p>GNE, or bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, myopathy presents with symptoms of foot drop, followed by lower and upper extremity muscle weaknesses and sparing of the quadriceps. Myopathies usually increase the risks of complications related to general anesthesia. The anesthetic management of patients with GNEmyopathy has not been previously reported. Herein, we report a case of GNEmyopathy in a 37-year-old woman and discuss anesthetic considerations for elective laparoscopic hysterectomy and bilateral salpingectomy, focusing on the postoperative airway management. We avoided administering neuromuscular-blocking agents and instead used a laryngeal mask airway.
The anesthetic management combining the use of a laryngeal mask airway and desflurane without neuromuscular-blocking agents provided sufficient abdominal and diaphragmatic muscle relaxations for sustaining the pneumoperitoneum for laparoscopic surgery.
... GNE myopathy is both clinically and genetically heterogeneous, which includes vacuolar myopathy sparing quadriceps (VMSQ) in Iranian Jews [4] and distal myopathy with rimmed vacuoles (DMRV) in Japanese individuals [11]. hIBM sole-ly refers to GNE myopathy in some literature [12] that shares clinical and histopathological features with sIBM, a commonly acquired muscle disease. ...
Objective:
The following study compared the pathological findings between sporadic inclusion body myositis (sIBM) and Glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase myopathy (GNEM) patients.
Methods:
An enzyme histochemistry was used to compare the pathological characteristics between 11 patients with sIBM and 16 patients with GNEM.
Results:
There were four pathological differences observed: (1) A majority of the rimmed vacuoles found in the sIBM patients resembled cracks, whereas the GNEM patients (P=0.004) had round or oval vacuoles. (2) A majority of the rimmed vacuoles that were located in the periphery of the atrophic muscle fibers of the sIBM patients. The patients with GNEM had a majority of the rimmed vacuoles in the center of the atrophic muscle fibers (P=0.001). (3) The patients with sIBM had basophilic granules in the rimmed vacuoles, which appeared to be fine granules that were sand-like particles. The GNEM patients had coarse granules (P=0.018). (4) The proportion of mononuclear cells invasion of muscle fibers was larger in the sIBM patients than the GNEM patients (P=0.047). The GNEM patients were younger on average than the sIBM patients at the onset of symptoms (P<0.001) and at the diagnosis age (P<0.001). The electromyography (EMG) showed the presence of myogenic lesions in 10 patients with sIBM, both myogenic and neurogenic lesions in one patients with sIBM and myogenic lesions in 16 patients with GNEM.
Conclusion:
There were significant differences in the morphologies of the rimmed vacuoles between sIBM patients and GNEM patients.
... Seither wurde diese Krankheitsentität nach der Erstbeschreiberin als "Distale Myopathie Typ Welander" bezeichnet. In der Folge wurden unter anderem durch N. G. Laing, W. R. Markesbery und R. C. Griggs, K. Miyoshi sowie I. Nonaka weitere distale Myopathien mit differentem klinischem Phänotyp dargestellt und unter Verwendung entsprechender Eponyme klassifiziert [4,[6][7][8]. Mit der zunehmenden Verfeinerung und Erweiterung genetischer Methoden gelang die Identifikation des zugrundeliegenden Genotyps für eine Reihe der vorgenannten Krankheitsbilder. ...
ZUSAMMENFASSUNG
Distale Myopathien stellen eine heteroge Gruppe von Erkrankungen dar, die sich durch einen prädominanten Befall körperferner Muskelgruppen auszeichnen und zunächst innerhalb weniger klinischer Phänotypen unter Verwendung von Eponymen klassifiziert worden sind. Genetische Hochdurchsatzverfahren haben das genotypische Spektrum der distalen Myopathien in den letzten Jahren erheblich erweitert. Ausgehend vom historischen Kontext wird die aktuelle Klassifikation distaler Myopathien vorgestellt, häufige Krankheitsbilder diskutiert und das diagnostische Vorgehen anhand eines strukturierten Handlungspfades erörtert.
... Onset of the disorder is in early adulthood and is rapidly progressive with involvement of the proximal muscles. DMAT is also similar to Nonaka myopathy (Nonaka, Sunohara et al. 1981) since the onset is on the anterior tibial muscles, but with higher CK levels. ...
The aim of this project was to build and apply tools for the analysis of muscle omics data, with a focus on Dysferlin deficiency. This protein is expressed mainly in skeletal and cardiac muscles, and its loss due to mutation (autosomal-recessive) of the DYSF gene, results in a progressive muscular dystrophy (Limb Girdle Muscular Dystrophy type 2B (LGMD2B), Miyoshi myopathy and distal myopathy with tibialis anterior onset (DMAT)). We have developed various tools and pipelines that can be applied towards a bioinformatics functional analysis of omics data in muscular dystrophies and neuromuscular disorders. These include: tests for enrichment of gene sets derived from previously published muscle microarray data and networking analysis of functional associations between altered transcripts/proteins. To accomplish this, we analyzed hundreds of published omics data from public repositories. The tools we developed are called CellWhere and MyoMiner. CellWhere is a user-friendly tool that combines protein-protein interactions and protein subcellular localizations on an interactive graphical display (https://cellwhere-myo.rhcloud.com). MyoMiner is a muscle cell- and tissue-specific database that provides co-expression analyses in both normal and pathological tissues. Many gene co-expression databases already exist and are used broadly by researchers, but MyoMiner is the first muscle-specific tool of its kind (https://myominer-myo.rhcloud.com). These tools will be used in the analysis and interpretation of transcriptomics data from dysferlinopathic muscle and other neuromuscular conditions and will be important to understand the molecular mechanisms underlying these pathologies.
... In this work, we report the first Italian family with SCCMS. The marked difficulty in reaching a diagnosis in this family was due to the presentation of a permanent distal weakness; this led initially to several different possible diagnoses including peripheral neuropathy, myotonic dystrophy, and distal myopathy (Welander distal myopathy [6], Laing distal myopathy due to a myosinopathy [7], or Nonaka type [8]). ...
Introduction
The slow-channel congenital myasthenic syndrome (SCCMS) is a postsynaptic form of congenital myasthenic syndromes (CMSs), a clinically heterogeneous group of disorders caused by genetic defects leading to an abnormal signal transmission at the endplate.
Methods
We report clinical and molecular data of a multigenerational family in which the presentation of a progressive proximal-distal weakness with ocular involvement led to a number of different clinical diagnoses.
Results
A comprehensive genetic study which included whole-genome linkage analysis and whole-exome sequencing identified a heterozygous missense substitution (c.721C>T, p.L241F) in the ε subunit of the acetylcholine receptor (CHRNE) that was consistent with clinical weakness in all patients.
Discussion
SCCMS is characterized by a broad and heterogeneous clinical phenotype in which disease onset, symptoms, severity, and progression can be highly variable even between family members. The identification of a CHRNE mutation allowed to make the definitive diagnosis of CMS in this family and contributed to define the clinical spectrum of this disease.
... GNE myopathy was reported for the first time around 1980, in Japan [6,7]. Due to its clinical characteristics, it has also been called distal myopathy with rimmed vacuoles (DMRV). ...
Background
GNE myopathy (distal myopathy with rimmed vacuoles) is a rare intractable muscle disease caused by the mutations in GNE gene, with no therapeutic agents at present. The mutations in GNE (UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase) gene result in a deficiency of the biosynthesis of aceneuramic acid. Aceneuramic acid improves the phenotype of GNE myopathy model mice. We examined the pharmacokinetics and safety of aceneuramic acid therapy in a nonrandomized manner for patients with GNE myopathy for the first time in humans.
Methods
This article was based on the world’s first Phase I trial and the additional Phase I trial that began at a time when the intermediate results of an overseas Phase II trial were ascertained. In the first trial, conventional tablets without controlled release were administered orally in a single dose of 800 mg, in 800 mg/doses given three times in 1 day, and in 800 mg/doses given three times per day for 5 days. Serum and urinary concentrations of total aceneuramic acid including aceneuramic acid bound to proteins and lipids were measured. Subsequently, administering extended-release tablets to patients with GNE myopathy, we investigated the pharmacokinetics and safety of a single 2000 mg dose, three doses given for 1 day, and three doses per day for 7 days.
Results
The results of the first trial showed no obvious increase in serum concentration after administration. Whereas the amount of aceneuramic acid excreted in the urine generally increased with all given doses, although there were variations among trial subjects. In the second trial, we measured free serum aceneuramic acid levels, and with all doses given there were obvious increases in the levels observed after administration. The degrees of increase were comparable with other studies conducted overseas, and there was no difference based on ethnicity. With regards to urinary excretion, free aceneuramic acid levels showed elevated levels in all patients, and total aceneuramic acid also increased in general, thus we could confirm the absorption of the investigational drug. In respect to safety, while some adverse events including abnormal laboratory test findings were observed, all events were mild and the causal relationship with the investigational drug was ruled out or unlikely.
Conclusion
The elevated serum concentration of aceneuramic acid and safety were confirmed. We decided that the trial could shift to the next level to examine the long-term efficacy and safety for Japanese patients as well.
Trial registration
NCT01236898, UMIN000011532. Registered 9 November 2010.
... [8,9]. The spectrum of classical clinical presentations which was initially described in 1981 and 1984 remained unchanged [1,2] and was complemented with broader spectrum of rarer and cohort specific symptoms. The first appearance of symptoms occurs most frequently in the third decade of life, although, few early onset cases (at 10 years of age) and late onset in the 5th decade have been reported [3]. ...
GNE myopathy is an ultra-rare autosomal recessive disease, which starts as a distal muscle weakness and ultimately leads to a wheelchair bound state. Molecular research and animal modelling significantly moved forward understanding of GNE myopathy mechanisms and suggested therapeutic interventions to alleviate the symptoms. Multiple therapeutic attempts are being made to supplement sialic acid depleted in GNE myopathy muscle cells. Translational research field provided valuable knowledge through natural history studies, patient registries and clinical trial, which significantly contributed to bringing forward an era of GNE myopathy treatment. In this review, we are summarising current GNE myopathy, scientific trends and open questions, which would be of significant interest for a wide neuromuscular diseases community.
Aims
Legg-Calve-Perthes disease (LCPD) is a diagnosis of exclusion. Various conditions, such as skeletal dysplasias, can closely mimic LCPD and these must be ruled out to provide appropriate treatment, prognosis, and counseling. Traditionally, genetic testing has not been readily available in pediatric orthopaedic practice. Furthermore, the clinical value of genetic testing patients with LCPD is unclear. With the advance of next-generation sequencing (NGS) technology, genetic testing has become clinically available as a lab test. The purposes of this study were to assess the clinical utility of genetic testing in select patients with LCPD and to determine the patient characteristics of those who tested positive for skeletal dysplasia.
Methods
This is an IRB-approved, retrospective study of 63 consecutive patients who presented with Perthes-like symptoms and/or x-ray findings and who had genetic testing. The reason(s) for genetic testing included bilateral hip disease, family history of LCPD, short stature, suspected skeletal dysplasia, atypical radiographic findings, and/or combinations of these reasons.
Results
Of the 63 patients, 19 patients (30%) were found to have a pathogenic gene variant. In 8 of the 19, a variety of skeletal dysplasia was diagnosed. The remaining 11 patients were found to be carriers of autosomal recessive disorders. All 19 patients were referred for genetic counseling. Of the 8 patients found to have skeletal dysplasia, 3 had bilateral disease, 3 were <10 percentile in height, 1 had a family history of “LCPD,” and 3 had atypical x-ray findings. In addition to the pathogenic variants, numerous genetic variants of unknown significance were found with 2 gene variants showing exactly the same variant found in 2 unrelated patients.
Conclusions
With 30% of the patients showing pathogenic results, genetic testing of select patients with Perthes-like disease is valuable in detecting an underlying genetic disorder or a carrier status of a genetic disorder.
Autosomal recessive Nonaka distal myopathy is a rare autosomal recessive genetic disease characterized by progressive degeneration of the distal muscles, causing muscle weakness and decreased grip strength. It is primarily associated with mutations in the GNE gene, which encodes a key enzyme of sialic acid biosynthesis (UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase). This study was performed to find GNE mutations in six independent distal myopathy patients with or without peripheral neuropathy using whole-exome sequencing (WES). In silico pathogenic prediction and simulation of 3D structural changes were performed for the mutant GNE proteins. As a result, we identified five pathogenic or likely pathogenic missense variants: c.86T>C (p.Met29Thr), c.527A>T (p.Asp176Val), c.782T>C (p.Met261Thr), c.1714G>C (p.Val572Leu), and c.1771G>A (p.Ala591Thr). Five affected individuals showed compound heterozygous mutations, while only one patient revealed a homozygous mutation. Two patients revealed unreported combinations of combined heterozygous mutations. We observed some specific clinical features, such as complex phenotypes of distal myopathy with distal hereditary peripheral neuropathy, an earlier onset of weakness in legs than that of hands, and clinical heterogeneity between two patients with the same set of compound heterozygous mutations. Our findings on these genetic causes expand the clinical spectrum associated with the GNE mutations and can help prepare therapeutic strategies.
Distal muscular dystrophies are primary hereditary muscle disorders with progressive loss of muscle tissue causing prominent weakness in hands and/or feet at onset. Some may progress to involve proximal muscles, while others remain mainly restricted to distal muscles. The age of onset and the histopathological findings are extremely variable. High throughput sequencing has further expanded the long list of genes associated with a distal muscular dystrophy. Currently, 19 genes (CAV3, CRYAB, DNAJB6, DNM2, FLNC, HNRNPA1, HSPB8, KLHL9, LDB3, MATR3, MB, MYOT, PLIN4, TIA1, VCP, NOTCH2NLC, LRP12, GIPC1, RILPL1) have been associated with an autosomal dominant form and four genes (ADSSL, ANO5, DYSF, GNE) are known causes of autosomal recessive forms. Disease-causing variants in five genes (ACTN2, DES, MYH7, NEB, RYR1 and TTN) result in either dominant or recessive distal muscular dystrophy and we have recently identified the first X-linked form due to SMPX mutations. An even more complex digenic mechanism has also been reported; rare pathogenic mutations in SQSTM1, previously identified with Paget disease of the bone, cause a distal muscular dystrophy when inherited in combination with a common polymorphism in TIA1.
This chapter describes the genetic background and the main clinical features of the currently known different forms of distal muscular dystrophy.
GNE myopathy is an adult onset disorder due to recessive mutations in the UDP N-acetylglucosamine 2- epimerase/N-acetylmannosamine kinase gene. It is a distal myopathy with relative sparing of the quadriceps manifesting usually in the third decade and slowly progressive to involve other limb muscles. Unusual features like proximal onset, neurogenic pattern and late respiratory involvement have been described. This is a worldwide disease with some high prevalence clusters due to founder mutations. Its typical muscle histology includes ‘rimmed’ vacuoles and cytoplasmic inclusions, thus it was called in the past hereditary inclusion body myopathy (HIBM) and distal myopathy with rimmed vacuoles (DMRV). Since GNE encodes a bi-functional enzyme, essential to sialic acid synthesis, sialylation defect is suspected as an important pathogenic factor, yet it does not fully explain the mechanism. Defects in this gene also account for macrothrombocytopenia and sialuria. Histopathology, imaging and other diagnostic features are reviewed. Potential therapeutic methods and future developments are discussed.
Distal myopathies are a group of genetic, primary muscle diseases. Patients develop progressive weakness and atrophy of the muscles of forearm, hands, lower leg, or feet. Currently, over 20 different forms, presenting a variable age of onset, clinical presentation, disease progression, muscle involvement, and histological findings, are known. Some of them are dominant and some recessive. Different variants in the same gene are often associated with either dominant or recessive forms, although there is a lack of a comprehensive understanding of the genotype-phenotype correlations. This chapter provides a description of the clinicopathologic and genetic aspects of distal myopathies emphasizing known etiologic and pathophysiologic mechanisms.
Background
A rare muscle disease, GNE myopathy is caused by mutations in the GNE gene involved in the sialic acid biosynthesis. Our recent phase II/III study has indicated that oral administration of aceneuramic acid to patients would slow disease progression.
Methods
We conducted a phase III, randomized, placebo-controlled, double-blind, parallel-group, multicenter study. Participants were assigned to receive an extended-release formulation of aceneuramic acid (SA-ER) or placebo. Changes in muscle strength and function over 48 weeks were compared between treatment groups using change in the upper extremity composite (UEC) score from baseline to Week 48 as the primary endpoint and the investigator-assessed efficacy rate as the key secondary endpoint. For safety, adverse events, vital signs, body weight, electrocardiogram, and clinical laboratory results were monitored.
Results
A total of 14 patients were enrolled and given orally SA-ER (n = 10) or placebo (n = 4) tablets. Decrease in least square mean (LSM) of change in UEC score at Week 48 with SA-ER (−0.115 kg) was numerically smaller as compared with placebo (−2.625 kg), with LSM difference (95% confidence interval) of 2.510 (−1.720 to 6.740) kg. In addition, efficacy rate was higher with SA-ER as compared with placebo. There were no clinically significant adverse events and other safety concerns observed.
Conclusions
The present study reproducibly showed the effect of orally administered SA-ER on slowing loss of muscle strength and function, indicating supplementation of sialic acid might be a promising replacement therapy for GNE myopathy.
Trial registration number: ClinicalTrials.gov (NCT04671472)
This major new edition fulfils the need for a single-volume, up-to-date information resource on the etiology, pathogenesis, diagnosis and treatment of diseases of skeletal muscles, including the muscular dystrophies, mitochondrial myopathies, metabolic myopathies, ion channel disorders, and dysimmune myopathies. As background to the clinical coverage, relevant information on advances in molecular and developmental biology, immunopathology, mitochondrial biology, ion-channel dynamics, cell membrane and signal transduction science, and imaging technology is summarized. Combining essential new knowledge with the fundamentals of history-taking and clinical examination, this extensively illustrated book will continue to be the mainstay for practising physicians and biomedical scientists concerned with muscle disease. Regular updates on the clinical and basic science aspects of muscle disease - written mainly by rising stars of myology - will be published on an accompanying website.
This major new edition fulfils the need for a single-volume, up-to-date information resource on the etiology, pathogenesis, diagnosis and treatment of diseases of skeletal muscles, including the muscular dystrophies, mitochondrial myopathies, metabolic myopathies, ion channel disorders, and dysimmune myopathies. As background to the clinical coverage, relevant information on advances in molecular and developmental biology, immunopathology, mitochondrial biology, ion-channel dynamics, cell membrane and signal transduction science, and imaging technology is summarized. Combining essential new knowledge with the fundamentals of history-taking and clinical examination, this extensively illustrated book will continue to be the mainstay for practising physicians and biomedical scientists concerned with muscle disease. Regular updates on the clinical and basic science aspects of muscle disease - written mainly by rising stars of myology - will be published on an accompanying website.
Riassunto
Una miopatia distale deve essere ipotizzata in presenza di un deficit motorio puro che inizia con un coinvolgimento dei muscoli distali degli arti inferiori e/o superiori. Negli ultimi anni sono stati identificati molti geni che possono essere rivelatori di una miopatia distale. Va tuttavia sottolineato che questi geni possono spesso essere responsabili anche di altre forme di miopatia, come la distrofia dei cingoli, le miopatie congenite o anche le neuropatie motorie. L’esame clinico e l’anamnesi specificano la topografia del deficit, l’età di insorgenza e la modalità di trasmissione. L’attenta ricerca di un aumento delle creatinfosfokinasi (CPK), di una cardiopatia, di un coinvolgimento faringeo e di una cataratta può fornire preziosi indizi per l’identificazione di queste miopatie distali. In un certo numero di casi, la biopsia muscolare resta indispensabile perché permette di precisare le caratteristiche istologiche della miopatia, in particolare la presenza o meno di vacuoli orlati e l’alterazione della rete miofibrillare, nonché di effettuare studi immunoistochimici sull’espressione di varie proteine il cui difetto o il cui accumulo possono essere responsabili di miopatie distali. Inoltre, la risonanza magnetica (RM) muscolare è divenuta uno strumento indispensabile per caratterizzare la topografia della lesione, a volte subclinica. Con l’arrivo delle tecniche di sequenziamento ad alto rendimento, il cui corollario è l’identificazione di numerose varianti di significato incerto, una precisa caratterizzazione fenotipica resta indispensabile per l’interpretazione dei risultati genetici.
Accumulating evidence has shown that Tau aggregates not only seed further tau aggregation within neurons but may also spread to neighboring cells and functionally connected brain regions. This process is referred to as “Tau propagation” and may explain the stereotypic progression of Tau pathology in the brains of Alzheimer’s disease (AD) patients. Tau filaments have distinct cellular and neuroanatomical distributions with morphological and biochemical differences, suggesting the ability to adopt disease-specific molecular conformations. These conformers may give rise to different neuropathological phenotypes, reminiscent of prion strains (strain hypothesis). Autophagy is one of the surveillance systems that contribute to protein homeostasis (proteostasis) through their degradation in lysosomes. The loss of proteostasis occurs with age and in neurodegenerative diseases, such as AD. Defective autophagy has been proposed to contribute to the accumulation of protein aggregates in the elderly brain and as well as the brains of patients with neurodegenerative conditions. In this chapter, we discuss the different Tau propagation mechanisms that may be involved in the cell-to-cell transmission of AD and related tauopathies. The mechanisms by which deficits in autophagic degradative pathways may contribute to the abnormal accumulation of tau in AD are also considered. Furthermore, the issue of pharmacological agents targeting specific tau species to promote the autophagic clearance of Tau from cells will be addressed. We propose our hypothesis that strain-specific autophagic degradation may contribute to the pathogenesis of tauopathies.
Autophagic vacuolar myopathy is a subgroup of muscle diseases defined as a condition in which autophagic vacuoles are present as a muscle pathological feature and is caused by abnormality of autophagy in skeletal muscles. In patients with inclusion body myositis (IBM), refractory slowly progressive muscular weakness in the extremities develops. In IBM, many autophagic vacuoles called rimmed vacuoles are present in muscle cells with deposition of Alzheimer’s disease (AD)-related proteins such as amyloid beta and phosphorylated tau, suggesting homology between IBM and AD. Danon disease is a hereditary disease associated with primary deficiency of lysosomal-associated membrane protein 2 in which cardiomyopathy and myopathy develop. This disease is characterized by the presence of specific autophagic vacuoles called autophagic vacuoles with sarcolemmal features (AVSF). The pathomechanism of Danon disease is considered to be caused by abnormality of autophagy resulting from primary lysosomal dysfunction.
Introduction:
GNE myopathy is an autosomal recessive distal myopathy caused by a biallelic mutation in UDP-N-acetylglucosamine 2-epomerase/N-acetylmannosamine kinase. In this study, we discuss the clinical features, pathological characteristics, genetic profiles, and atypical clinical manifestations of 22 Chinese GNE patients.
Materials and methods:
Retrospective analysis was performed for GNE myopathy patients at our institute between 2005 and 2021. Histopathological analysis and gene testing were done according to standard protocols.
Results:
Molecular analysis revealed 14-reported and 7 novel mutations, including c.125G > A (p.P42Q), c.226G > A (p.V76I), c.970C > G (p.H324D), c.155A > G (p.D52G), c.1055G > A (p.R352H), c.1064G > A (p.G355E), and c.491 T > C (p.I164T) in GNE. D207V was the most frequent mutation showing an allele frequency of 25%. A total of 21 patients presented classic clinical manifestation, and only 1 patient had signs of proximal muscle weakness. A patient containing p.V603L and p.R160X mutations showed idiopathic thrombocytopenia and distal weakness. There were 4 female patients who experienced rapid deterioration after pregnancy.
Discussion:
Our study revealed 7 novel mutations in GNE, where p.D207V was shown as a potential hotspot mutation in Chinese patients. Idiopathic thrombocytopenia should be a concern in GNE myopathy patients. Twenty-seven percent of female patients experienced rapid deterioration during pregnancy or after delivery.
GNE myopathy is an autosomal recessive adult‐onset distal myopathy caused by biallelic variants in the GNE gene, which encodes a protein with two key enzymatic activities in the biosynthesis of sialic acid. In 1981, there was a report of a Japanese family in which muscle biopsies showed rimmed vacuoles in tibialis anterior with relative sparing of the quadriceps muscles. Twenty years later, the causative gene was identified to be GNE. Our group has constructed a mouse model that recapitulates the symptoms of GNE myopathy in patients and demonstrates the therapeutic effects of oral sialic acid supplementation on muscle phenotypes. The first clinical trial of N‐acetylneuraminic acid (NeuAc) was conducted in 2010 at Tohoku University, and several clinical trials are now underway at multiple sites. Patient registries have also been started, including the Japanese Registry of Muscular Dystrophy (Remudy, established in 2012) and the online international GNE Myopathy Disease Monitoring Program (launched in 2014). These registries have allowed collection of comprehensive patient data, including new clinical features suggesting that GNE myopathy is not only a disease of skeletal muscle. In this review, we summarize the history of research on GNE myopathy and discuss the mechanism of the disease and its more recently identified features.
Upper body muscle involvement has never been systematically investigated in GNE myopathy (GNEM). Aims of our study were to explore upper body involvement in GNEM patients by means of muscle MRI, to compare the degree of pathology with that of lower body and to validate the MRI pattern of the lower limbs in novel patients.
MRI scans of 9 GNEM patients were retrospectively evaluated. T1-weighted and short-tau inversion recovery images were scored.
As a result, serratus anterior was involved in all patients, followed by subscapularis and trapezius muscles. The majority of scans consistently showed hypotrophy of pectoralis minor. Conversely, cranial muscles including the tongue were always spared while pectoralis major and latissimus dorsi were relatively spared. We confirmed the known pattern of involvement in the pelvic girdle and limbs, that were more significantly affected than the upper girdle in all disease stages. Paraspinal muscles were also frequently affected displaying both a cranio-caudal and latero-medial gradient of severity along the body axis.
Upper girdle MRI highlights a selective muscle involvement in GNEM, offering an added value in patients’ diagnostic workup and deep stratification.
The diagnostic evaluation of a patient with suspected hereditary muscle disease can be challenging. Clinicians rely largely on clinical history and examination features, with additional serological, electrodiagnostic, radiologic, histopathologic, and genetic investigations assisting in definitive diagnosis. Hematological testing is inexpensive and widely available, but frequently overlooked in the hereditary myopathy evaluation. Hematological abnormalities are infrequently encountered in this setting; however, their presence provides a valuable clue, helps refine the differential diagnosis, tailors further investigation, and assists interpretation of variants of uncertain significance. A diverse spectrum of hematological abnormalities is associated with hereditary myopathies, including anemias, leukocyte abnormalities, and thrombocytopenia. Recurrent rhabdomyolysis in certain glycolytic enzymopathies co-occurs with hemolytic anemia, often chronic and mild in phosphofructokinase and phosphoglycerate kinase deficiencies, or acute and fever-associated in aldolase-A and triosephosphate isomerase deficiency. Sideroblastic anemia, commonly severe, accompanies congenital-to-childhood onset mitochondrial myopathies including Pearson marrow-pancreas syndrome and mitochondrial myopathy, lactic acidosis, and sideroblastic anemia phenotypes. Congenital megaloblastic macrocytic anemia and mitochondrial dysfunction characterize SFXN4-related myopathy. Neutropenia, chronic or cyclical, with recurrent infections, infantile-to-childhood onset skeletal myopathy and cardiomyopathy are typical of Barth syndrome, while chronic neutropenia without infection occurs rarely in DNM2-centronuclear myopathy. Peripheral eosinophilia may accompany eosinophilic inflammation in recessive calpainopathy. Lipid accumulation in leukocytes on peripheral blood smear (Jordans' anomaly) is pathognomonic for neutral lipid storage diseases. Mild thrombocytopenia occurs in autosomal dominant, childhood-onset STIM1 tubular aggregate myopathy, STIM1 and ORAI1 deficiency syndromes, and GNE myopathy. Herein, we review these hereditary myopathies in which hematological features play a prominent role.
Muscular dystrophies have long been recognized as heterogeneous inherited disorders, characterized by progressive skeletal muscle degeneration, weakness, and dystrophic changes in muscle biopsy. These diseases are known to have autosomal dominant, recessive, or X-linked inheritance. The increasing understanding of genetic and biological pathology of these diseases has resulted in a tremendous increase in therapeutic approaches for many of these disorders and newly approved drugs for Duchenne muscular dystrophy, the most common childhood muscular dystrophy. A multidisciplinary approach to the diagnosis and management of muscular dystrophies remains of paramount importance.
Duchenne and Becker muscular dystrophy (DMD/BMD) are commonly inherited muscle disorders. We report a 31-year-old male who had muscle symptoms with left-right differences and intellectual disability. He was diagnosed with BMD at age 15 primarily based on muscle biopsy findings. A few years later, DMD gene analysis revealed that he was a heterozygous carrier of a normal copy of the gene and a mutated copy with an exon 45-54 deletion, which is expected to result in an out-of-frame mutation. A karyotype analysis was compatible with XXY Klinefelter's syndrome. The analysis of X-chromosome inactivation (XCI) using his skeletal muscle sample revealed a skewed XCI pattern. This is the first reported case of a symptomatic male carrier of DMD caused by skewed XCI in Klinefelter's syndrome with a genetically proven heterozygous mutation of the DMD gene. The skewed XCI pattern could also explain the left-right differences in skeletal muscle symptoms observed in this patient.
We report a case of 2 sisters in their 20s with genetically confirmed UDP-N-acetylglucoasmine 2-epimerase/N-acetylmannosamine kinase myopathy along with muscle biopsy findings. Both patients described slowly progressive signs of distal-predominant weakness since adolescence that had been dismissed as "clumsiness." Exam and electrodiagnostic testing suggested a predominately distal myopathy. Muscle biopsy of the left tibialis anterior revealed rimmed vacuoles and, interestingly, also had characteristic features of a myofibrillar myopathy. Genetic testing confirmed a diagnosis of autosomal recessive GNE myopathy in both patients. GNE myopathy has not typically been considered a myofibrillar myopathy, but this case raises possibilities worthy of further exploration. It is possible that the unique combination of pathogenic alleles in GNE reported here has led to a novel form of GNE myopathy with muscle biopsy showing characteristic features of GNE myopathy and myofibrillar myopathy. The other possibility is that myofibrillar myopathy may be a more common feature of GNE myopathies than classically described.
Muskeldystrophien sind eine klinisch und pathogenetisch heterogene Gruppe progressiver Muskelerkrankungen, die zu einer primären Degeneration von Muskelfasern führen. Das Manifestationsalter reicht von der frühen Kindheit bis in das späte Erwachsenenalter. Bei vielen Formen ist der zugrunde liegende Gendefekt bekannt, und es erfolgt eine genetische Klassifikation. Auch die kongenitalen Myopathien, die bereits kurz nach der Geburt klinisch manifest werden, stellen mittlerweile eine große Gruppe von Myopathien dar.
Altered autophagy accompanied by abnormal autophagic (rimmed) vacuoles detectable by light and electron microscopy is a common denominator of many familial and sporadic non‐inflammatory muscle diseases. Even in the era of next generation sequencing (NGS), late‐onset vacuolar myopathies remain a diagnostic challenge.
We identified 32 adult vacuolar myopathy patients from 30 unrelated families, studied their clinical, histopathological and ultrastructural characteristics and performed genetic testing in index patients and relatives using Sanger sequencing and NGS including whole exome sequencing (WES).
We established a molecular genetic diagnosis in 17 patients. Pathogenic mutations were found in genes typically linked to vacuolar myopathy (GNE, LDB3/ZASP, MYOT, DES, GAA), but also in genes not regularly associated with severely altered autophagy (FKRP, DYSF, CAV3, COL6A2, GYG1, TRIM32) and in the digenic facioscapulohumeral muscular dystrophy 2. Characteristic histopathological features including distinct patterns of myofibrillar disarray and evidence of exocytosis proved to be helpful to distinguish causes of vacuolar myopathies. Biopsy validated the pathogenicity of the novel mutations p.(Phe55*) and p.(Arg216*) in GYG1 and of the p.(Leu156Pro) TRIM32 mutation combined with compound heterozygous deletion of exon 2 of TRIM32 and expand the phenotype of Ala93Thr‐caveolinopathy and of limb‐girdle muscular dystrophy 2i due to FKRP mutation. In 15 patients no causal variants were detected by Sanger sequencing and NGS panel analysis. In 12 of these cases, WES was performed, but did not yield any definite mutation or likely candidate gene. In one of these patients with a family history of muscle weakness, the vacuolar myopathy was eventually linked to chloroquine therapy.
Our study illustrates the wide phenotypic and genotypic heterogeneity of vacuolar myopathies and validates the role of histopathology in assessing the pathogenicity of novel mutations detected by NGS. In a sizable portion of vacuolar myopathy cases, it remains to be shown whether the cause is hereditary or degenerative.
Inherited neuromuscular diseases are a heterogeneous group of rare diseases for which the low general awareness leads to frequent misdiagnosis. Advances in DNA sequencing technologies are changing this situation, and it is apparent that these diseases are not as rare as previously thought. Knowledge of the pathogenic variants in patients is helping in research efforts to develop new therapies. Here we present a review of current knowledge in GNE myopathy, a rare neuromuscular disorder caused by mutations in the GNE gene that catalyzes the biosynthesis of sialic acid. The most common initial symptom is foot drop caused by anterior tibialis muscle weakness. There is a progressive wasting of distal skeletal muscles in the lower and upper extremities as well. The quadriceps is relatively spared, which is a distinguishing feature of this disease. The characteristic histological features include autophagic rimmed vacuoles with inclusion bodies. GNE variant analysis of Indian patients has revealed a founder mutation (p.Val727Met) common within the normal Indian populations, especially in the state of Gujurat. We discuss therapeutic options, including metabolite supplementation, pharmacological chaperones, and gene therapy. Initiatives that bring together patients, researchers, and physicians are necessary to improve knowledge and treatment for these rare disorders.
Distal myopathies are a group of rare muscle diseases characterized by distal weakness at onset. Although acquired myopathies can occasionally present with distal weakness, the majority of distal myopathies have a genetic etiology. Their age of onset varies from early‐childhood to late‐adulthood while the predominant muscle weakness can affect calf, ankle dorsiflexor or distal upper limb muscles. A spectrum of muscle pathological changes, varying from nonspecific myopathic changes to rimmed vacuoles to myofibrillar pathology to nuclei centralization, have been noted. Likewise, the underlying molecular defect is heterogeneous. In addition, there is emerging evidence that distal myopathies can result from defective proteins encoded by genes causative of neurogenic disorders, be manifestation of multisystem proteinopathies or the result of the altered interplay between different genes. In this review, we provide an overview on the clinical, electrophysiological, pathological and molecular aspects of distal myopathies, focusing on the most recent developments in the field.
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Four cases of distal myopathy in 2 families are reported. In all the cases the parents were first cousins. Three male cases among 4 siblings in one family were typically affected and their younger sister who was rather thin, and showed an increased excretion of creatine in urine, was thought to have a risk of affection in the future. In the other family only one female case among 7 siblings was observed. One of her elder sisters had suffered from a similar disorder. The onsets of the disease were at 29, 32, 33 and 35 yr of age, respectively. Muscular weakness and atrophy began from the distal portion of the lower extremities, and in 3 cases the proximal muscles were affected also. Slight weakness of the sternocleidomastoid muscle was demonstrated in one case. In 3 cases there was no obvious difference in the degree of affection between the flexor and extensor of mucles in the upper extremities, but the flexor muscles were more markedly affected in the lower extremities. Impotence was noted in one case. The activity of creatine phosphokinase showed a slightly high level in 2 of 3 cases tested. LDH isozyme, in one of 2 cases tested, showed an abnormal pattern similar to that of progressive dystrophy. Electromyographic changes were myopathic. The histopathological findings of the biopsied muscles were myopathic; there was variation in the diameter of fibers, an increase and central emigration of sarcolemmal nuclei, vacuolar degeneration and proliferation of the connective tissue, and in one case, the long chains of nuclei.
Kugelberg (1947) found certain positive electromyographic criteria for the diagnosis of primary myopathies. Without this discovery there is no reason to believe that the dystrophy-simulating juvenile muscular atrophy would have been distinguished in Sweden. Also for further investigations and differential diagnosis of distal late myopathy this discovery was invaluable.
Ultrastructural studies have shown plasmalemmal defects in a proportion of non-necrotic muscle fibers in Duchenne dystrophy, suggesting that intracellular calcium overloading may be an important mechanism of muscle fiber degeneration. To investigate this assumption, we studied the localization of calcium with the von Kóssa method, with alizarin red, and with glyoxalbis-(o-hydroxyanil) in serial, fresh-frozen sections of 114 biopsy specimens. The biopsy material included Duchenne dystrophy (24 cases), other dystrophies (27 cases), inflammatory myopathies (47 cases), and normal controls (11 cases). Counted in each specimen were every muscle fiber, the so-called large-dark fibers, and all calcium-positive fibers. Separate counts were made of the large-dark, necrotic, and other types of calcium-positive fibers. In Duchenne dystrophy, non-nectotic calcium-positive fibers occurred with a mean frequency of 4.83 percent. For all other groups, the corresponding value was 0.57 percent, with a range of 0.21 percent (normals) to 1.76 percent (scleroderma), p less than 0.001. Large-dark fibers were 12 times more common in Duchenne dystrophy than in all other cases. Forty-three percent of the fibers were calcium-positive in Duchenne dystrophy, whereas calcium-positive large-dark fibers were extremely rare in the other cases.
Studies of sarcolemmal integrity with extracellular Procion Yellow gave evidence of structural defects in a high percentage of muscle fibers in Duchenne dystrophy and in vitamin E-deficiency myopathy in the guinea pig. The dye entered fibers in these conditions more often than in controls. Myofibrillary clumping occurred in the region of major penetration of the dye. It seems likely that sarcolemmal defects occur in vivo in these conditions, allowing the entry of high concentrations of calcium into the sarcoplasm with consequent fiber damage. The biochemical basis of these sarcolemmal defects remains to be elucidated. Our procedure for biopsy of the vastus medialis muscle may prove useful in preparing a limb muscle for in vitro physiologic studies.
Histochemical and histopathological staining methods were applied to muscle biopsy material from 13 patients with distal myopathy of late onset. Six cases showed slight to moderate histopathological changes and the normal distinction between Type I and Type II muscle fibres, based on their staining characteristics for myofibrillar ATPase, was well preserved. A selective Type I atrophy and an irregular distribution of oxidative enzyme and fat staining in Type I fibres were evident. In the other 7 cases, with moderate to advanced histopathological changes, there was a marked blurring of the normal difference observed in ATPase activity between Type I and TYpe II fibres. Thus, both types of fibre exhibited a high intensity of staining for myofibrillar ATPase at pH 9.4 without inhibition by acid preincubation (pH 4.3). These changes in phosphatase activity were found not only in atrophic fibres but also in normal-sized fibres without other signs of degeneration. Nuclear proliferation in chains and "ring fibres" were found. The early histopathological and histochemical changes in distal myopathy are strikingly similar to those of myotonic dystrophy.
This report describes the clinical, laboratory, and muscle biopsy histochemical and electron microscopic studies of one inherited and two sporadic cases of distal myopathy. Histopathologic and histochemical studies showed numerous myopathic alterations and no significant evidence of denervation. Electron microscopic studies showed a broad spectrum of nonspecific alterations similar to those in other forms of muscular dystrophy. Autophagic vacuoles were prominent in all cases. The inherited case was characterized by an unusual focal granular degeneration that, ultrastructurally, was composed of homogeneous fine granules devoid of other organelles or myofilamens.
We report six cases of inclusion body myositis (IBM), a distinct but infrequently recognized inflammatory disease of skeletal muscle. Clinically, IBM differs from dermatomyositis and polymyositis. It lacks features of collagen-vascular disease, has a relatively benign and protracted course, frequently involves distal muscles, is found mainly in males, and does not improve with corticosteroid treatment. Electronmicroscopic demonstration of abnormal filaments in muscle cells is necessary for definite diagnosis, but IBM may be suspected by the finding on cryostat sections of numerous hematoxylinophilic granules in "lined" vacuoles in muscle cells. These correspond to whorls of cytomembranes. Although in dermatomyositis the capillary network is partly destroyed, in IBM it is usually augmented. A viral etiology of IBM has been suggested but remains unproven.
Study of biopsies from 30 boys with Duchenne muscular dystrophy suggests that necrosis of muscle cells is initiated by loss of plasma membrane, followed, after a short interval, by Z disc lysis and mitochondrial changes to constitute the picture of fully developed necrosis. Empty basal lamina tubes containing collagen indicated that regeneration may fail to occur. The tubes form a basis for collagen deposition. Evidence suggests that small patches of membrane loss can be repaired, though a slice of superficial cytoplasm is lost, and a piece of detached basal lamina results. The markedly hypercontracted fibres seen did not show features of necrosis.
The study of a family affected with hereditary distal myopathy with onset in early infancy is presented. Complete neurological examination was necessary in several members of the two last generations to discover the existence of the abnormalities of which they were unaware. The propositus was the most affected member of the family iwth distal paresis of the upper and lower extremities and selective paresis of the deltoid muscles. In addition he had kyphoscoliosis, talipes valgus and limitation of mobility of several joints. The onset of the disease was estimated as before the age of 2 when the child started walking. There was no progression of the disease. Clinical examination suggested a myopathic origin of the condition. A sural nerve biopsy was normal. Light-microscopy histochemical studies disclosed a predominance of type I fibres which were at the same time hypotrophic. Subsarcolemmal deposits of mitochondria were present although they were scanty and of normal ultrastructural appearance. In view of the morphological presentation it is postulated that this disease should be classified within the groups of myopathies accompanied by disproportion of fibres and selective atrophy of type I fibres.
In 6 patients with Duchenne dystrophy, electron microscopical studies of concanavalin A (Con A) binding sites using the peroxidase labeling technique revealed a population of muscle fibers in which the reaction at the cell surface was irregular and patchy in areas larger than 0.5 mu. In 5 control subjects, such focal alterations were not observed and the reaction appeared continuous and regular. The findings indicate focal abnormalities at the muscle cell surface of Con A receptors in Duchenne dystrophy.
With the exception of the large series of adult-onset hereditary distal myopathy from Sweden, few cases of primary muscle disease with a definite distal predilection have been published. We report 3 sporadic cases of distal myopathy with the following features: (1) early adult onset (26 to 33 years); (2) slowly progressive weakness affecting first the distal leg muscles and later the arms; (3) marked elevation of creatine phosphokinase (more than 10 times the normal value); and (4) electromyographic and histological evidence of myopathy in distal muscles. The differential diagnosis is discussed and other reported cases are reviewed. The differences between hereditary cases reported by others and the sporadic cases reported here form the basis for a tentative subclassification of this syndrome.
A kindred is described in which six members, and probably a seventh, have been affected by a late-onset distal myopathy. Detailed clinical, laboratory, biopsy and autopsy findings are described in two family members. Myopathic histologic changes were observed in numerous biopsy and autopsy muscle specimens. Cardiomyopathy was present in one case.
Nineteen patients with long-standing muscular wasting are described in whom the clinical and investigative data suggest a chronic disorder of anterior horn cells. They have been presented in a number of broad groups based upon the distribution of weakness and it is suggested that this grouping may bear some relationship to an aetiological classification, although exceptions probably occur.Patients showing a symmetrical distribution of weakness most commonly have a family history of the disease, and a genetically-determined metabolic defect is probably responsible in most of these cases. Several metabolic defects may occur, and some possible factors influencing the resulting distribution of weakness have been discussed.Some of the remaining patients are probably suffering from “conventional” motor neurone disease of unusually slow progression.The results of investigation are discussed and further examples are described showing in some cases EMG features suggestive of a myopathic disorder.
SINCE GOWERS'1 description of distal myopathy in 1902, the specific aspects of this disorder have remained the subject of controversy. Some investigators suggest that a majority of patients with distal myopathy have atypical forms of myotonic dystrophy, Charcot-Marie-Tooth, or motor neuron disease. An important advance in the understanding of this problem was made in 1951 when Welander2 clearly proved the existence of a distal myopathy, which she called "distal late hereditary myopathy." The clinical characteristics of this disorder include dominant inheritance, onset between the ages of 20 and 77 years of age (mean 47 years) with similar features in men and women, and slow progression. The disease begins with paresis and atrophy of the extensor and small muscles of the distal portion of the extremities. In most patients, weakness seems to start in the hands, causing clumsiness in performing fine movements. Electromyograms and muscle biopsies confirm
Muscle biopsies in 4 cases of Duchenne muscular dystrophy and two normal controls were examined by electron microscopy using lanthanum as a tracer for assessment of the T-system. Lanthanum was localized in the extracellular spaces, the basement membranes, intercellular spaces between muscle fibers and satellite cells, subsarcolemmal vesicles (caveola), motor end-plate, and the T-system in the controls. The T-system was sometimes connected with the caveolae, and was located at right angles to the myofibrils in the controls. In Duchenne muscular dystrophy, the T-system showed irregularities of position, tangle formations and dilatation of the diameters when observed using lanthanum as a tracer, even in muscle fibers which under light- and electron-microscopic examinations did not show any changes. Structure of the triad was destroyed and lanthanun was localized in the sarcoplasmic reticulum (SR). The changes of the T-system and triad seemed to play an important role in the high level of creatine phosphokinase (CPK) in the serum of Duchenne muscular dystrophy patients who do not show any clinical symptoms. Because of the destruction of the triad, CPK will easily flow out to the exterior of muscle fibers via the T-system.
Undifferentiated type 2C fibers, which are dark on ATPase staining with both alkaline and acid preincubation, comprised on average 16.1% of the muscle fibers in 12 patients with Duchenne muscular dystrophy (DMD). Many of type 2C fibers had characteristics of regenerating fibers: basophilic cytoplasm, vesicular nuclei with occasional prominent nucleoli, high alkaline phosphatase and nonspecific esterase activity, and also high oxidative enzyme activity at the periphery of the fiber. A localized high acetylcholinesterase activity suggested the presence of a neuromuscular junction in some of the type 2C fibers. In serial sections, histochemical reactions characteristic of the type 2C fiber were present in segments of a single fiber, which in other parts was either a type 1 or a type 2 fiber. Since most of the opaque (hyaline, dark) fibers, which previously have been thought to be precursors of necrotic fibers, behaved as differentiated type 1 or type 2 fibers, the presence of type 2C fibers in DMD may not reflect "dedifferentiation" of fiber type, but rather indicate an active regenerating process. It remains unknown whether the type 2C fiber segments in DMD develop into fully differentiated functional fibers or remain as incompletely regenerated fibers.
A family with a hitherto unrecognized type of distal myopathy is described. The disorder appears to be of late onset and to be inherited through a dominant autosome. It has a more malignant course than the distal myopathies described earlier, from which it can be differentiated clinically by an early involvement of thenar muscles and hand flexors. The key to the correct diagnosis is provided by the morphological and immunohistological investigation of muscle biopsies, which show typical sarcoplasmic bodies and an abundance of intermediate-sized (skeletin) filaments.
Calcium-activated neutral protease (CANP) was demonstrated in myofibrils, especially at the Z-band in chicken glycerinated myofibrils, by an immunofluorescent method. The amount of CANP bound to myofibrils was approximately 4 percent of that contained in the whole muscle homogenate. No immunological difference was recognized between the myofibril-bound CANP and the soluble one when examined by Ouchterlony's immunodiffusion analysis. A possible role of myofilbril-bound CANP in the physiological turnover of the myofibrillar proteins is discussed.
Although changes in proteolysis in muscle tissue are now well documented for a variety of physiological and pathological conditions, the mechanism of degradation of cellular protein during normal protein turnover remains to be elucidated. Data from several laboratories have suggested the involvement of alkaline serine proteinases. Recent studies have questioned these results, and demonstrated that the serine proteinases are of mast cell origin and are not present in muscle cells. The only proteinases to date that have been shown to be present in muscle cells and capable of degrading myofibrillar proteins are Ca2+-activated proteinase, cathepsin B, and cathepsin D. Recent interest and developing awareness of endogenous enzyme inhibitors in cells may unmask many new enzymes.
The presence of intermediate filaments in various mature and immature eukaryotic cells is well documented. By using antibodies against the intermediate (skeletin) filaments of cow heart Purkinje fibres, we have in the present work analyzed the distribution of skeletin in normal and diseased skeletal muscle fibres. Antiskeletin proved to be a useful tool for the identification of regenerating fibres in Duchenne muscular dystrophy. In mature muscle fibres with well-preserved myofibrils, skeletin had an intermyofibrillar localization at the Z-disk level where intermediate filaments were demonstrated. The presence of skeletin was also demonstrated around the rods of muscle fibres in nemaline myopathy biopsies, but the rods themselves did not show any cross-reactivity. This report exemplifies the usefulness of antibodies in muscle pathology.
Rimmed vacuoles (Dubowitz and Brooke 1973) have been found in 12 cases with various neuromuscular diseases and are considered to be autophagic in nature. They consisted of multilaminated membranous structures accompanied by glycogen granules, dense bodies, and amorphous, granular, and fibrillar material. The contents of the vacuoles were regarded as having partially dissolved out of the vacuoles in cryostat sections but some were plastered along the walls of the vacuoles and were depicted by the staining procedures for light microscopy. The "lined vacuoles" described by Carpenter et al. (1978) in inclusion body myositis closely agree with the rimmed vacuoles in respect of histochemical and ultrastructural features.
Diseased human muscle in tissue culture — A new approach to the pathogenesis of human neuromuscular disorders
- Askanas
Askanas, V. and W. K. Engel (1977) Diseased human muscle in tissue culture --A new approach to the pathogenesis of human neuromuscular disorders. In : L.P. Rowland (Ed.), Pathogenesis of Human Muscular Dystrophy, Excerpta Medica, Amsterdam, pp. 85f~874. Barrows, H. S. and L. P. Duemler (1962) Late distal myopathy-Report of a case, Neurology (Minneap.), 12: 547-550.
A review of the morphologic features and consequences of muscle cell necrosis in Duchenne disease — Clues to the pathogenesis
- Karpati
A case report of sporadic distal myopathy, with special reference to vacuolar degeneration and rod-like body in muscle fibers.
- Miyoshi S.
- Santa T.
- Ohta M.
- Araki S.
Autosomal recessive distal muscular dystrophy — A new variety of distal muscular dystrophy predominantly seen in Japan.
- Miyoshi K.
- Iwasa M.
- Kawai H.
- Sasaki N.
- Kusaka K.
- Yagita M.
- Hiasa M.
- Tada Y.
Distal myopathy A variety characterized by prominent vacuolar degeneration of muscle.
- Mizusawa H.
- Nakano I.
- Inoue K.
- Takagi A.
- Mannen T.
- Toyokura Y.
Distal myopathy — A case of non-hereditary distal myopathy.
- Murone I.
- Sato T.
- Shirakawa K.
- Yamada K.
- Kanbayashi K.
Myopathia distalis tarda hereditaria
- Walender
Ultrastructure of “opaque fibers” (OFs) in Duchenne muscular dystrophy (DMD)
- Chou
Duchenne dystrophy — Electron microscopic findings pointing to a basic or early abnormality in the plasma membrane of the muscle fiber.
- Mokri B.
- Engel A.G.
The distribution of intermediate filament protein (skeletin) in normal and diseased human skeletal muscle — An immunohistochemical and electron-microscopic study.
- Thornell L.-E
- Edström L.
- Eriksson A.
- Henriksson K.-G
- Ägqvist K.-A
Distal myopathy A variety characterized by prominent vacuolar degeneration of muscle
- Mizusawa
A case report of sporadic distal myopathy, with special reference to vacuolar degeneration and rod-like body in muscle fibers
- Miyoshi
Autosomal recessive distal muscular dystrophy — A new variety of distal muscular dystrophy predominantly seen in Japan
- Miyoshi
Distal myopathy — A case of non-hereditary distal myopathy
- Murone