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genes
G C A T
T A C G
G C A T
Case Report
The First Case of Congenital Myasthenic Syndrome
Caused by a Large Homozygous Deletion in the
C-Terminal Region of COLQ (Collagen Like Tail
Subunit of Asymmetric Acetylcholinesterase) Protein
Nicola Laforgia 1, Lucrezia De Cosmo 1, Orazio Palumbo 2, Carlotta Ranieri 3, Michela Sesta 4,
Donatella Capodiferro 1, Antonino Pantaleo 3, Pierluigi Iapicca 5, Patrizia Lastella 6,
Manuela Capozza 1, Federico Schettini 1, Nenad Bukvic 7, Rosanna Bagnulo 3and
Nicoletta Resta 3, 7, *
1Section of Neonatology and Neonatal Intensive Care Unit, Department of Biomedical Science and Human
Oncology (DIMO), University of Bari “Aldo Moro”, 70124 Bari, Italy; nicola.laforgia@uniba.it (N.L.);
dlucrezia@yahoo.com (L.D.C.); dottcapodiferro@virgilio.it (D.C.); manuelacapozza26@gmail.com (M.C.);
federico.schettini@uniba.it (F.S.)
2Division of Medical Genetics, Fondazione IRCCS Casa Sollievo della Sofferenza,
71013 San Giovanni Rotondo, Italy; o.palumbo@operapadrepio.it
3Division of Medical Genetics, Department of Biomedical Sciences and Human Oncology (DIMO),
University of Bari “Aldo Moro”, 70124 Bari, Italy; ranieri.carlotta@gmail.com (C.R.);
antonino.pantaleo@uniba.it (A.P.); rosanna.bagnulo@uniba.it (R.B.)
4Neurology Unit, University Hospital Consortium Corporation Polyclinic of Bari, 70124 Bari, Italy;
m_sesta@virgilio.it
5SOPHiA GENETICS SA HQ, 1025 Saint-Sulpice, Switzerland; PIapicca@sophiagenetics.com
6Rare Diseases Centre—Internal Medicine Unit “C. Frugoni”, Polyclinic of Bari, 70124 Bari, Italy;
patrizia.lastella76@gmail.com
7Medical Genetics Section, University Hospital Consortium Corporation Polyclinic of Bari, 70124 Bari, Italy;
nenad.bukvic@policlinico.ba.it
*Correspondence: nicoletta.resta@uniba.it; Tel.: +39-0805593619
Received: 17 November 2020; Accepted: 15 December 2020; Published: 18 December 2020
Abstract:
Congenital myasthenic syndromes (CMSs) are caused by mutations in genes that encode
proteins involved in the organization, maintenance, function, or modification of the neuromuscular
junction. Among these, the collagenic tail of endplate acetylcholinesterase protein (COLQ; MIM 603033)
has a crucial role in anchoring the enzyme into the synaptic basal lamina. Here, we report on the first
case of a patient with a homozygous deletion affecting the last exons of the COLQ gene in a CMS patient
born to consanguineous parents of Pakistani origin. Electromyography (EMG), electroencephalography
(EEG), clinical exome sequencing (CES), and single nucleotide polymorphism (SNP) array analyses
were performed. The subject was born at term after an uneventful pregnancy and developed significant
hypotonia and dystonia, clinical pseudoseizures, and recurring respiratory insufficiency with a need
for mechanical ventilation. CES analysis of the patient revealed a homozygous deletion of the COLQ
gene located on the 3p25.1 chromosome region. The SNP-array confirmed the presence of deletion that
extended from exon 11 to the last exon 17 with a size of 19.5 Kb. Our results add new insights about
the underlying pathogenetic mechanisms expanding the spectrum of causative COLQ mutations. It is
relevant, considering the therapeutic implications, to apply suitable molecular approaches so that no
type of mutation is missed: “each lost mutation means a baby treated improperly”.
Keywords: COLQ; congenital myasthenic syndrome; clinical exome sequencing; SNP-array
Genes 2020,11, 1519; doi:10.3390/genes11121519 www.mdpi.com/journal/genes
Genes 2020,11, 1519 2 of 8
1. Introduction
Congenital myasthenic syndromes (CMSs) are a group of genetically and clinically heterogeneous
disorders with impaired neuromuscular transmission and symptoms such as fatigable skeletal muscle
weakness generally confined to ocular, bulbar, or limb-girdle muscles [
1
]. CMSs can be inherited
in either an autosomal recessive or autosomal dominant manner; however, the autosomal recessive
manner is more frequently observed.
CMSs differ from myasthenia gravis, an autoimmune disorder that affects the same anatomic region,
because of early age of onset, positive family history, rarity, and lack of response to immunomodulatory
drugs. Clinical presentation of CMSs is highly heterogeneous and ranges from mild symptoms to severe
manifestations, sometimes with life-threatening respiratory episodes especially in the first decade of
life [
2
]. All subtypes of CMSs share the clinical features of fatigability and muscle weakness, but the
age of onset, presenting symptoms, and response to treatment relate to different genetic defects [
3
].
CMSs should be suspected in the case of early-onset fatigable muscle weakness, which especially
affects the ocular, bulbar, and limb muscles, positive family anamnesis, clinical and neurophysiological
myasthenic findings with a negative antibody testing profile, and abnormalities of electromyography
(EMG) [
4
]. Affected patients may also present dysmorphisms, neuropathic pain, seizures, pterygia,
contractures, hyperlaxity of joints, abnormal speech, cognitive impairment, respiratory insufficiency,
or skeletal deformities.
Onset can be prenatal, during infancy, childhood, or adolescence (rare). Clinical onset may
sometimes be in adulthood with EMG changes not present in all muscles and intermittent [5].
The most common cause of CMS is a molecular defect impacting the function (CHRNA1, CHRNB,
CHRND, CHRNE and CHRNG) or the clustering (RAPSN, DOK7, MUSK, LRP4) of muscle nicotinic
acetylcholine receptors at the neuromuscular junction. CMS can also be caused by mutations in genes
encoding proteins in the synaptic basement membrane (COLQ, AGRN, LAMB2), in the presynaptic
release machinery (CHAT, VACHT, SLC5A7, SYT2, SNAP25B)
,
or in protein glycosylation (GFPT1,
DPAGT1, ALG2 and ALG14) [3].
Intra- and inter-familial phenotypic heterogeneity have been described with the same genotype
and a possible gender effect [
6
]. Thirty CMS disease genes have been identified, and all are functionally
involved in the development and maintenance of neuromuscular endplate. Of these, the collagenic
tail of endplate acetylcholinesterase (COLQ; MIM 603033) forms a triple helix collagenic tail required
for the anchoring of acetylcholinesterase to the synaptic basement membrane. Different mutations
have now been identified in each COLQ domain and, depending on their location, they can affect the
assembly with catalytic subunits or prevent the formation of the triple collagen helix [
3
]. We present
the first report of a homozygous deletion of the C-terminal region of the COLQ protein in a Pakistani
boy with CMS and epilepsy born to healthy parents (first cousins) identified by the clinical exome
sequencing (CES) approach integrated with a copy number analysis algorithm. This approach
expands the genotype–phenotype correlation of CMS and improves genetic counseling and access to
precision medicine.
2. Materials and Methods
2.1. Patient Recruitment
Written informed consent to perform genetic testing and further studies were obtained from the
family using a form approved by the competent ethics committee in line with the principles of the
Declaration of Helsinki and any other applicable local ethical and legal requirements (approval code
6631-prot. N◦93990/03/12/2020).
2.2. Clinical Exome Sequencing (CES)
Next generation sequencing analysis was performed on genomic DNA from peripheral venous
blood (QIAamp DNA Blood Mini Kit) with a clinical exome sequencing panel kit. Approximately 11 Mb
Genes 2020,11, 1519 3 of 8
(114.405 exons) of the conserved coding regions that cover >4500 genes were enriched with
>150,000 probes, which were designed based on human genome sequences (Sophia Genetics SA,
Saint Sulpice, Switzerland). Library preparation and sequencing were performed according to the
manufacturer’s protocol on MiSeq Instrument (Illumina, San Diego, CA, USA). The mean depth of
coverage was 70
×
. Raw data were analyzed using SOPHiA
™
DDM (Sophia Genetics SA) with algorithms
for alignment including single nucleotide polymorphisms (SNPs), and insertions/deletions (Pepper
™
,
Sophia Genetics SA patented algorithm), and copy number variations (Muskat
™
, Sophia Genetics SA
patented algorithm). The raw reads were aligned to the human reference genome (GRCh37/hgl9),
and an integrative genomics viewer (IGV) was used visualize the binary alignment map (BAM) files.
2.3. SNP-Array Analysis
High resolution SNP-array analysis of the proband and his parents was carried out by using the
CytoScan HD array (Thermo Fisher Scientific, Waltham, MA, USA) as previously described [7,8].
This array contains more than 2.6 million markers for copy number variations (CNVs) analysis
and approximately 750,000 SNP probes capable of genotyping with an accuracy greater than 99%.
Data analysis was performed using the Chromosome Analysis Suite Software version 4.1
(Thermo Fisher Scientific) following a standardized pipeline described in literature [
8
]. Base pair
positions, information about genomic regions and genes affected by CNVs, and known associated
disease have been derived from the University of California Santa Cruz (UCSC) Genome Browser,
build GRCh37 (hg19).
3. Results
3.1. Clinical History
This was the fourth child of first cousin parents born at term (3470 g at 41 weeks) after an uneventful
pregnancy. One neonatal death for unknown causes was reported. The child was discharged home
after three days (Figure 1).
Genes 2020, 11, x FOR PEER REVIEW 3 of 8
>150,000 probes, which were designed based on human genome sequences (Sophia Genetics SA, Saint
Sulpice, Switzerland). Library preparation and sequencing were performed according to the
manufacturer’s protocol on MiSeq Instrument (Illumina, San Diego, CA, USA). The mean depth of
coverage was 70×. Raw data were analyzed using SOPHiA™ DDM (Sophia Genetics SA) with
algorithms for alignment including single nucleotide polymorphisms (SNPs), and
insertions/deletions (Pepper™, Sophia Genetics SA patented algorithm), and copy number variations
(Muskat™, Sophia Genetics SA patented algorithm). The raw reads were aligned to the human
reference genome (GRCh37/hgl9), and an integrative genomics viewer (IGV) was used visualize the
binary alignment map (BAM) files.
2.3. SNP-Array Analysis
High resolution SNP-array analysis of the proband and his parents was carried out by using the
CytoScan HD array (Thermo Fisher Scientific, Waltham, MA, USA) as previously described [7,8].
This array contains more than 2.6 million markers for copy number variations (CNVs) analysis
and approximately 750,000 SNP probes capable of genotyping with an accuracy greater than 99%.
Data analysis was performed using the Chromosome Analysis Suite Software version 4.1
(Thermo Fisher Scientific) following a standardized pipeline described in literature [8]. Base pair
positions, information about genomic regions and genes affected by CNVs, and known associated
disease have been derived from the University of California Santa Cruz (UCSC) Genome Browser,
build GRCh37 (hg19).
3. Results
3.1. Clinical History
This was the fourth child of first cousin parents born at term (3470 g at 41 weeks) after an
uneventful pregnancy. One neonatal death for unknown causes was reported. The child was
discharged home after three days (Figure 1).
Figure 1. Pedigree chart of the family. Squares and circles indicate men and women, respectively. A
diagonal line through a symbol indicates a deceased individual. A small rhombus indicates a
miscarriage. Affected individuals are indicated by filled symbols. Carrier individuals are indicated
by filled-empty symbols. II-4 genetic analysis revealed a homozygous microdeletion involving the
3p25.1 chromosome region that contains part of the collagenic tail of endplate acetylcholinesterase
(COLQ) gene. The microdeletion resulted in heterozygous status in I-1 and I-2.
At 55 days of life (DOL), he was brought to the emergency department (ED) of a local hospital
for dyspnea and cyanosis. He was intubated and ventilated and developed tonic-clonic fits during
hospitalization that were treated successfully with phenobarbitone. He was then discharged after 15
days but was then admitted to our department at DOL84 because of hypotonia, weight loss, and
difficult feeding. Weight, length, and head circumference were all <3° centile for his age. Marked
hypotonia, dystonia, mild palpebral ptosis, and electroclinic fits (chaotic movements, hyperextension
of arms and legs followed by marked hypotonia, apnea and cyanosis) with partial response to
Figure 1.
Pedigree chart of the family. Squares and circles indicate men and women, respectively.
A diagonal line through a symbol indicates a deceased individual. A small rhombus indicates a
miscarriage. Affected individuals are indicated by filled symbols. Carrier individuals are indicated by
filled-empty symbols. II-4 genetic analysis revealed a homozygous microdeletion involving the 3p25.1
chromosome region that contains part of the collagenic tail of endplate acetylcholinesterase (COLQ)
gene. The microdeletion resulted in heterozygous status in I-1 and I-2.
At 55 days of life (DOL), he was brought to the emergency department (ED) of a local hospital
for dyspnea and cyanosis. He was intubated and ventilated and developed tonic-clonic fits during
hospitalization that were treated successfully with phenobarbitone. He was then discharged after 15 days
but was then admitted to our department at DOL84 because of hypotonia, weight loss, and difficult
feeding. Weight, length, and head circumference were all <3
◦
centile for his age. Marked hypotonia,
dystonia, mild palpebral ptosis, and electroclinic fits (chaotic movements, hyperextension of arms
Genes 2020,11, 1519 4 of 8
and legs followed by marked hypotonia, apnea and cyanosis) with partial response to different drugs
(levetiracetam, carbamazepine, midazolam, clonazepam, vitamin B6, and vigabatrin) were evident.
Electroencephalography (EEG) showed theta–delta waves starting from the right occipital region with
contralateral spread followed by the depression of the brain’s electrical activity linked to a cyanosis
crisis (Figure 2A–D). Cerebral MRI revealed a normal brain structure except for mild enlargement of
the subarachnoid space. He was discharged after four months at the age of eight months and was
treated with levetiracetam with no new episodes of convulsions.
Figure 2.
Electroencephalography (EEG). (
A
,
B
) High voltage slow waves from right occipital areas with
bilateral involvement. Video EEG recording showed associated chaotic movements. (
C
,
D
) Occipital
bilateral slow waves with suppression of electrical activity. Video EEG recording showed apnea and
lack of motion.
Palpebral ptosis became more evident at 12 months. The EMG revealed a decremental response to
repetitive nerve stimulation on the deltoid muscle at a frequency of 3 Hz. The EMG showed a decrease
in the amplitude of motor unit potential (MUP) with no post-increment. Treatment was started with
noninvasive ventilation (NIV) during nocturnal sleep and pyridostigmine. Pyridostigmine was started
at the dose of 0.78 mg/kg/day in four divided doses. There was only improvement of the ptosis,
no effects on apnea and respiratory crisis. Pyridostigmine was then stopped at 18 months after genetic
diagnosis of COLQ mutation, and both 3–4 diaminopyridine and salbutamol treatments were started
with positive effects on muscular tone and a significant reduction in the apnea and respiratory crisis.
The child is now 20 months old with a mild neuromotor delay. He can walk with support. NIV during
sleep is still needed.
3.2. Genetic Findings
CES of the patient identified a homozygous microdeletion of part of the COLQ gene and
heterozygous status in both parents (Figure 3A). The deleted exons identified by CES were exons 13–17.
No other significant single nucleotide variants (SNVs) in genes related to the clinical features were
detected. SNP-array analysis confirmed the homozygous deletion involving the 3p25.1 chromosome
region. The deleted region was 19.5 Kb in size and was covered by 24 SNP-array probes. The SNP-array
demonstrated the deletion of exons 11–17 of the COLQ gene, which was wider than that revealed by
CES analysis. The discrepancy between the SNP-array and NGS results may reflect the limitation of
the CNV-detection algorithm of the latter technology for large panels due to coverage fluctuations,
as CNV resolution is based on the coverage levels of the target regions. No other CNVs were
Genes 2020,11, 1519 5 of 8
detected apart from known polymorphisms. The molecular karyotype of the patient according
to the International System for Human Cytogenetic Nomenclature (ISCN 2016) is: arr[GrCh37]
3p25.1(15491478x1,15492150_15511615x0,15511740x1). The deleted region in 3p25.1 contains part of the
COLQ gene (i.e., exons 11–17). Carrier testing in the parents was performed by chromosome microarray
analysis (CMA) using the same platform (i.e., CytoScan HD Array) and resulted in heterozygous
outcomes in both (Figure 3B).
Figure 3.
Schematic representation of the COLQ gene and results of single nucleotide polymorphism
(SNP)-array analysis in the patient and his parents (
A
) COLQ exons with 28 published pathogenic
variants (upper part) and the microdeletion described in this study (lower part). Three COLQ domains:
(1) conserved domains of COLQ include an N-terminal proline-rich attachment domain (PRAD) that
associates each COLQ strand with an acetylcholinesterase tetramer, (2) a central collagen domain that
contains two heparan sulfate proteoglycan binding (HSPBP) domains, and (3) a C-terminal region
needed for assembly of the COLQ strands in a triple helix. (
B
) Results of SNP-array analysis in the
patient and his parents. The copy number state of each probe is drawn along chromosome 3 from
15.44 to 15.56 Mb (University of California Santa Cruz (UCSC) Genome Browser, buildGRCh37/hg19).
The upper panel represents the copy number state of the proband, the middle panel that of the father,
and the lower panel that of the mother. Values on the Y-axis indicate the inferred copy number
according the probes’ intensities. Red bars indicate the deletion identified in the patient (homozygous
state, copy number =0) and his parents (heterozygous state, copy number =1).
Genes 2020,11, 1519 6 of 8
4. Discussion
The usual clinical pattern of CMSs is characterized by abnormal fatigability either permanent or
fluctuating with weakness of extra-ocular, facial, bulbar, axial, respiratory, or limb muscles. There is
often hypotonia with developmental delay. Generalized muscle hypotonia and weakness, feeding
difficulties, poor suck and cry, and developmental delay may also be the first signs of CMS [9].
Progressive respiratory failure is also associated with CMSs. In 2002, Byring et al. described
sudden episodes of respiratory distress and bulbar weakness in CMSs elicited by infections, fever,
and stress [
10
]. In some cases, significant apnea may require intubation and rapid initiation of
ventilation support.
In our patient, the main signs of CMSs in the first month of life were chaotic movements followed
by apnea needing ventilation without the typical clinical features of CMS.
The EEG did not show seizures and the observed chaotic movements of our patient have not
been previously described in CMSs, in which muscular weakness and fatigue, with secondary clinical
manifestations, are typical.
We believe that, during the first months of life of our patient, his muscular response was still not
profoundly compromised so that chaotic movements mimicking seizures represented his physiological
response to the reduced gas exchange due to respiratory impairment, triggered by different factors,
such as viral infections.
In other words, before the typical respiratory insufficiency with apnea and the need for artificial
ventilation of CMS-affected patients, he was still able during the early phase of his disease, he was still
able to partially react to the developing asphyxia, i.e., acidosis and hypoxemia.
These chaotic movements soon followed by apnea with the need of assisted ventilation did
not occur thereafter, i.e., after the age of six months. They could be interpreted as well as choking
spells, already reported in patients with CMS, that occur when the musculature is not yet severely
compromised [11].
CMSs are caused by mutations in genes that encode proteins involved in the organization,
maintenance, function, or modification of the neuromuscular junction (NMJ) [
3
]. Age of onset,
presenting symptoms, and response to treatment vary depending on the molecular mechanism that
results from the underlying genetic defect. In our patient, we identified a mutation of the COLQ gene
that encodes a multidomain functional protein of the NMJ crucial for anchoring acetyl cholinesterase
(AChE) to the basal lamina and its accumulation at the NMJ [12].
Mutations in COLQ cause AChE deficiency. Patients severely affected by COLQ mutations
abolish AChE activity present during infancy [
3
,
13
]. Less severely affected patients with residual
enzyme activity present during childhood and become disabled later in life. The weakness can affect
all voluntary muscles but can spare the ocular muscles, and in a few patients, the weakness has a
limb–girdle distribution. Clinically, COLQ-related CMSs present with a broad range of features and
severity, but the clinical manifestations are usually severe and can include respiratory failure, as in our
patient [14].
However, biallelic COLQ mutations are responsible for a minority of CMSs cases with mutations
that have been described in each of the three COLQ domains. To date, most reported COLQ mutations
are uniformly distributed on the three conserved domains of COLQ protein: proline-rich attachment
domain (PRAD) [exons 1–4] in the N-terminal region, heparan sulfate proteoglycan-binding domain
(HSPBD) in the collagen domain [exons 4–14], and the C-terminal region [exons 15–17]. The causative
mutations would exert their effects by different mechanisms resulting in prolonged synaptic currents
and different action potentials due to expanded residence of acetylcholine in the synaptic space. Most of
the COLQ gene mutations are nonsense, frameshift, splicing, or missense. Mutations localized in the
N-terminal domain prevent the collagen domain from associating with the catalytic subunits, and those
in the collagen domain affect the assembly of the triple-helical collagen domain. Most mutations in the
C-terminal domain reduce COLQ expression or prevent the triple helical assembly (Figure 3A) [3].
Genes 2020,11, 1519 7 of 8
To date, multiexon COLQ deletion has been described only in the two following cases. In 1998,
Ohno et al. [
15
] reported a heterozygous truncation mutation consisting of a large-scale frameshift
deletion [exon 2–3] in a CMS patient that abolished PRAD and followed the domain of the COLQ gene.
Twenty years later, Wang et al. [
16
] identified a novel copy number deletion encompassing exon 14 and
exon 15 of the COLQ gene in compound heterozygosity with the IVS16 +3A >G variant.
Our case is the first report of a CMS harboring a homozygous extended deletion of 19.5 kb
encompassing exon 11–17 of the COLQ gene (Figure 3A). This mutation truncates half of the collagen
domain consisting of GXY triplets and one of the two HSPB domains as well as the entire C-terminal
domain. It could be particularly damaging considering that the cationic residues of the HSPB
domain interact with the anionic residues in the synaptic basal lamina and help the anchoring of
the COLQ protein and the C-terminal region needed for assembly of the COLQ strands in a triple
helix. The homozygous state of the deletion was identified. The crucial role of the domains involved
could explain the severe clinical presentation in our patient. Congenital myasthenic syndromes are
rare diseases; the prevalence of CMS is estimated at one tenth that of myasthenia gravis, which has a
prevalence of 25:1.000.000–125:1.000.000 [11]. CMS also has genotypic and phenotypic heterogeneity;
thus, therapy of CMSs is only symptomatic, and several drugs may exhibit severe side effects. The most
frequently used drugs are AchE-inhibitors [
14
], 4-diaminopyridine [
17
], salbutamol [
18
], ephedrine [
14
],
and fluoxetine [19].
In our case, the EMG revealed a myasthenic pattern. As our patient needed NIV during the night
to sleep due to recurrent apnea, pyridostigmine was started. Only a partial response (reduction in
palpebral ptosis) was obtained but after the molecular diagnosis, pyridostigmine was stopped
and salbutamol was given, leading to a significant reduction in apnea and respiratory insufficiency.
This finding highlights the importance of timely genetic counselling because the final diagnosis is crucial
for correct CMSs treatment. Non-pharmacological treatments rely on physiotherapy, speech therapy,
and occupational therapy. Sometimes invasive treatments are needed such as nasal intermittent
positive pressure ventilation (NIPPV) during the night or the entire day in case of respiratory failure.
PEG is used in the case of dysphagia, failure-to-thrive, or a nutritional disturbance. Surgical corrections
are performed for severe deformities [20].
Prognosis and outcome of CMSs derive only from observational studies, case studies, and case
reports because prospective outcome studies are not available. Due to the clinical variability, outcome and
prognosis may vary considerably accordingly to various CMS types and infections. Fever or psychosocial
stress could also have a negative effect on the outcome of these patients [
1
]. Our case report confirms
the clinical heterogeneity of patients with CMS, indicating that recurrent apnea and respiratory crises
during the first months of life could be responsible of electro-clinic seizures.
Author Contributions:
Conceptualization, N.L. and N.R.; Methodology, C.R., P.I. and R.B.; Software, P.I.;
Validation, N.R., N.L., M.C., M.S., D.C., F.S., N.B. and L.D.C.; Investigation N.L., N.R., M.S. and O.P.; Data curation,
M.S., D.C., F.S., R.B., P.L., L.D.C. and C.R.; Writing—original draft preparation, N.R., M.C., O.P., A.P. and
N.L.; Writing—review and editing, N.R., N.L., N.B. and L.D.C.; Supervision, N.R.; Project administration, N.R.
All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding
Acknowledgments: We are extremely grateful to the family who took part in this study.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. Finsterer, J. Congenital myasthenic syndromes. Orphanet J. Rare Dis. 2019,14, 57. [CrossRef] [PubMed]
2.
Maggi, L.; Bernasconi, P.; D’Amico, A.; Brugnoni, R.; Fiorillo, C.; Garibaldi, M.; Astrea, G.; Bruno, C.;
Santorelli, F.M.; Liguori, R.; et al. Italian recommendations for diagnosis and management of congenital
myasthenic syndromes. Neurol. Sci. 2019,40, 457–468. [CrossRef] [PubMed]
3.
Engel, A.G.; Shen, X.-M.; Selcen, D.; Sine, S.M. Congenital myasthenic syndromes: Pathogenesis, diagnosis,
and treatment. Lancet Neurol. 2015,14, 420–434. [CrossRef]
Genes 2020,11, 1519 8 of 8
4.
De Souza, P.V.S.; Batistella, G.N.D.R.; Lino, V.C.; Pinto, W.B.V.D.R.; Annes, M.; Oliveira, A.S.B. Clinical and
genetic basis of congenital myasthenic syndromes. Arq. Neuro-Psiquiatria
2016
,74, 750–760. [CrossRef]
[PubMed]
5.
Cruz, P.M.R.; Palace, J.; Beeson, D. Inherited disorders of the neuromuscular junction: An update. J. Neurol.
2014,261, 2234–2243. [CrossRef] [PubMed]
6.
Ardissone, A.; Moroni, I.; Bernasconi, P.; Brugnoni, R. Congenital myasthenic syndrome: Phenotypic
variability in patients harbouring p.T159P mutation in CHRNE gene. Acta Myol.
2017
,36, 28–32. [PubMed]
7.
Palumbo, O.; Fichera, M.; Palumbo, P.; Rizzo, R.; Mazzolla, E.; Cocuzza, D.M.; Carella, M.; Mattina, T. TBR1 is
the candidate gene for intellectual disability in patients with a 2q24.2 interstitial deletion. Am. J. Med. Genet.
Part A 2014,164, 828–833. [CrossRef] [PubMed]
8.
Palumbo, O.; Palumbo, P.; Di Muro, E.; Cinque, L.; Petracca, A.; Carella, M.; Castori, M. A Private 16q24.2q24.3
Microduplication in a Boy with Intellectual Disability, Speech Delay and Mild Dysmorphic Features. Genes
2020,11, 707. [CrossRef] [PubMed]
9.
Barisic, N.; Müller, J.; Paucic-Kirincic, E.; Gazdik, M.; Lah-Tomulic, K.; Pertl, A.; Serti ´c, J.; Zurak, N.;
Lochmüller, H.; Abicht, A. Clinical variability of CMS-EA (congenital myasthenic syndrome with episodic
apnea) due to identical CHAT mutations in two infants. Eur. J. Paediatr. Neurol.
2005
,9, 7–12. [CrossRef]
[PubMed]
10.
Byring, R.; Pihko, H.; Tsujino, A.; Shen, X.-M.; Gustafsson, B.; Hackman, P.; Ohno, K.; Engel, A.G.;
Udd, B. Congenital myasthenic syndrome associated with episodic apnea and sudden infant death.
Neuromuscul. Disord. 2002,12, 548–553. [CrossRef]
11.
Abicht, A.; Müller, J.S.; Lochmüller, H. Congenital Myasthenic Syndromes; Adam, M.P., Ardinger, H.H.,
Pagon, R.A., Wallace, S.E., Bean, L.J.H., Mefford, H.C., Stephens, K., Amemiya, A., Ledbetter, N., Eds.;
GeneReviews; University of Washington: Seattle, WA, USA, 2016.
12.
Arredondo, J.; Lara, M.; Ng, F.; Gochez, D.A.; Lee, D.C.; Logia, S.P.; Nguyen, J.; Maselli, R.A. COOH-terminal
collagen Q (COLQ) mutants causing human deficiency of endplate acetylcholinesterase impair the interaction
of ColQ with proteins of the basal lamina. Hum. Genet. 2014,133, 599–616. [CrossRef] [PubMed]
13.
Hutchinson, D.O.; Walls, T.J.; Nakano, S.; Camp, S.; Taylor, P.; Harper, C.M.; Groover, R.V.; Peterson, H.A.;
Jamieson, D.G.; Engel, A.G. Congenital endplate acetylcholinesterase deficiency. Brain
1993
,116, 633–653.
[CrossRef] [PubMed]
14.
Al-Shahoumi, R.; Brady, L.I.; Schwartzentruber, J.; Tarnopolsky, M. Two cases of congenital myasthenic
syndrome with vocal cord paralysis. Neurology 2015,84, 1281–1282. [CrossRef] [PubMed]
15.
Ohno, K.; Brengman, J.; Tsujino, A.; Engel, A.G. Human endplate acetylcholinesterase deficiency caused by
mutations in the collagen-like tail subunit (ColQ) of the asymmetric enzyme. Proc. Natl. Acad. Sci. USA
1998,95, 9654–9659. [CrossRef] [PubMed]
16.
Wang, W.; Wu, Y.; Wang, C.; Jiao, J.; Klein, C.J. Copy number analysis reveals a novel multiexon deletion of
the COLQ gene in congenital myasthenia. Neurol. Genet. 2016,2, e117. [CrossRef] [PubMed]
17.
Andreux, F.; Hantaï, D.; Eymard, B. Congenital myasthenic syndromes phenotypic expression and
pathophysiological characterisation. Rev. Neurol. 2004,160, 163–176. [CrossRef]
18.
Padmanabha, H.; Saini, A.G.; Sankhyan, N.; Singhi, P. COLQ-Related Congenital Myasthenic Syndrome and
Response to Salbutamol Therapy. J. Clin. Neuromuscul. Dis. 2017,18, 162–163. [CrossRef] [PubMed]
19.
Chaouch, A.; Müller, J.S.; Guergueltcheva, V.; Dusl, M.; Schara, U.; Rakoˇcevi´c-Stojanovi´c, V.; Lindberg, C.;
Scola, R.H.; Werneck, L.C.; Colomer, J.; et al. A retrospective clinical study of the treatment of slow-channel
congenital myasthenic syndrome. J. Neurol. 2012,259, 474–481. [CrossRef] [PubMed]
20.
Maselli, R.A.; Ng, J.J.; A Anderson, J.; Cagney, O.; Arredondo, J.; Williams, C.; Wessel, H.B.; Abdel-Hamid, H.;
Wollmann, R.L. Mutations in LAMB2 causing a severe form of synaptic congenital myasthenic syndrome.
J. Med. Genet. 2009,46, 203–208. [CrossRef] [PubMed]
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