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Sirenomelia, also called mermaid syndrome, is a rare lethal multi-system congenital deformity with an incidence of one in 60,000–70,000 pregnancies. Sirenomelia is mainly characterized by the fusion of lower limbs and is widely associated with severe urogenital and gastrointestinal malformations. The presence of a single umbilical artery...
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... classified into several categories based on the wide variety of limb malformation phenotypes. Saint-Hilaire and Forster classified sirenomelia based on the number of feet. The other widely used classification is the Stocker and Heifetz method, which has seven types (I-VII) and is based on the presence or absence of the femur, tibia, and fibula ( Fig. 1) [2,5,6]. Other, less commonly used classifications include the Kjaer method based on the iliac-sacral distance (ISD) ...Citations
... Some patients might survive up to one year if urogenital and anus surgeries are performed. Sirenomelia may exhibit various associated leg deformities, prompting further subclassification based on the specific anatomical variations observed [1,7,[17][18][19][20]. ...
Background: Caudal regression syndrome (CRS) is a rare congenital malformation characterized by incomplete development of the lower spine and spinal cord. Its estimated incidence ranges from 1 to 2 per 100,000 live births, leading to a spectrum of clinical presentations. Although most cases are diagnosed during childhood, only a small number of cases have been documented in adults in the medical literature. Case Report: A 27-year-old woman underwent an outpatient magnetic resonance imaging (MRI) of the thoracolumbar spine due to severe lower back pain experienced for the first time. Despite congenital leg abnormalities and multiple childhood surgeries, no further investigations were conducted at that time. MRI revealed congenital anomalies consistent with CRS, including coccygeal agenesis, L5 sacralization, and spinal cord defects. The patient also had a long-standing pilonidal cyst treated conservatively, now requiring operative treatment due to an abscess. Conclusions: This report underscores a rare case of CRS initially misdiagnosed and mistreated over many years. It emphasizes the importance of considering less common diagnoses, especially when initial investigations yield inconclusive results. This clinical case demonstrates a highly valuable and educative radiological finding. In the literature, such cases with radiological findings in adults are still lacking.
... Sirenomelia is an extreme form of caudal regression characterized by a fusion of the lower limbs and a variable combination of associated anomalies. 4 Case Reports Case 1 A 30 year old primigravida spontaneous conception came for a routine first trimester scan at gestation of 12 weeks and 1 day. There was no history of consanguineous marriage, maternal diabetes, or drug intake. ...
Caudal dysplasia or caudal regression sequence is a congenital malformation that is characterized by maldevelopment of the lower half of the body with variable involvement of the gastrointestinal, genitourinary, skeletal, and nervous system. Most cases are sporadic and associated with the presence of a single umbilical artery. We report three cases with varying morphological spectrum of caudal dysplasia diagnosed during the first trimester ultrasound.
... Thus, sirenomelia can be classified as a severe form of caudal regression spectrum. 2,3,11,12 The underlying event's intensity, onset, and duration all affect how variable the phenotype is Garrido-Allepuz et al. 12 In other words, during embryonal development, a single "hit" may result in abnormalities in many progenitor fields, leading to polytypic manifestations. The time and intensity of the hit determine the heterogeneity. ...
... 13 (2) The vascular steal phenomenon, where the distal aorta is atretic, and one intra-abdominal artery is present, leads to the redirection of blood from caudal structures to the placenta and results in anomalies of caudal structures. 2,11 In 11 cases by Stevenson et al., a single large artery in the abdominal cavity was present, pushing the vascular steal theory forward. 4,14 However, a single umbilical artery can also be found in some patients with caudal regression syndrome and normal umbilical arteries in some patients with sirenomelia. ...
Sirenomelia is a rare lethal multi-systemic birth malformation in which the two lower limbs are replaced with a rotated single midline tail-like limb. Several hypotheses try to explain this syndrome, with the most prominent theories being the “vascular steal hypothesis” and the “defective blastogenesis hypothesis.” We report a case of a baby with sirenomelia who had a single femur and a single tibia, which classify the case as type VI on Stocker and Heifetz classification. The only risk factor in our case is young maternal age. The baby had a single umbilical artery, a prominent feature of the vascular steal hypothesis. Nonetheless, it also had upper limb deformity, which can be better explained by the defective blastogenesis hypothesis. Our case supports the defective blastogenesis theory of sirenomelia more than the vascular steal hypothesis as it has both a single umbilical artery and upper limb deformity. Also, our case serves as a teaching lesson that indicates the importance of an obstetric ultrasound before a cesarean section has to be done to avoid unnecessary surgery for life incompatible congenital anomaly.
... Four additional cases were also published: two in 2015 (Samal & Rathod, 2015) and two in 2021 (Shojaee et al., 2021). ...
The etiology of sirenomelia is currently unknown. Data are limited in comparing external and internal abnormalities using modern imaging technologies and molecular genetic analysis. The purpose of the current study was designed to compare external and internal anatomical defects in two cases of sirenomelia and Potter's sequence. Considered rare, Potter's sequence is a fetal disorder with characteristic features of bilateral renal agenesis, obstructive uropathy, atypical facial appearance, and limb malformations. The internal and external malformations of two term fetuses with sirenomelia and Potter's sequence were compared using assessment of external features, radiography and MRI on internal structures, and molecular genetic studies on sex determination. Data reveal that both fetuses were male and manifested with an overlapping but distinct spectrum of abnormalities. Principal differences were noted in the development of the ears, brain, urogenital system, lower limbs, pelvis, and vertebral column. Defects of the axial mesoderm are likely to underlie the abnormalities seen in both fetuses. The first one, which had only caudal defects, was found to have a spectrum of abnormalities most similar to those associated with more severe forms of the small pelvic outlet syndrome, although the structure and orientation of the sacrum and iliae were different from previously reported cases. The other had both caudal and cranial defects, and was most similar to those described in the axial mesodermal dysplasia syndrome. Defects associated with sirenomelia can be evaluated with standard gross anatomy examination, radiology, MRI, and modified PCR techniques to determine anatomical abnormalities and the sex of preserved specimens, respectively. Evidence indicated that sirenomelia could be developed via various etiologies.
... Acredita-se que os radicais livres de oxigênio, cuja produção aumenta no diabetes materno, exerçam um efeito teratogênico no desenvolvimento embrionário levando a essa anomalia (AL HADHOUD et al., 2017;RAMPHUL;MEJIAS;RAMPHUL-SICHARAM, 2018;TURGUT et al., 2017). Além disso, a idade da mãe está fortemente associada à sirenomelia; por exemplo, idades maternas inferiores a 20 ou superiores a 40 anos estão mais ligadas à anomalia (SHOJAEE et al., 2021). ...
Introdução: A sirenomelia é uma condição caracterizada pelo desenvolvimento anormal do corpo caudal de um feto, com fusão parcial ou completa da extremidade inferior, sendo também conhecida como Síndrome da Sereia. A anomalia é uma malformação grave multissistêmica, geralmente envolvendo os sistemas gastrointestinal, geniturinário, cardiovascular e musculoesquelético. A causa exata da sirenomelia é desconhecida, e acredita-se que fatores ambientais e genéticos possam desempenhar um papel no desenvolvimento da referida anomalia. O prognóstico da sirenomelia é ruim, com uma sobrevida média de menos de uma semana e mais da metade dos casos terminam em natimortos. Objetivo: Relatar um caso de sirenomelia atendido em nosso Serviço. Método: Trata-se do relato do caso de uma gestante atendida no Serviço de Ginecologia e Obstetrícia do Hospital Universitário São Francisco na Providência de Deus – HUSF, localizado na cidade de Bragança Paulista - SP. Relato do Caso: Paciente primigesta, 17 anos, encaminhada ao Serviço de Medicina Fetal após a realização de ultrassonografia morfológica durante a gravidez que demonstrou múltiplas malformações, incluindo agenesia renal e oligoâmnio severo. A criança nasceu prematura e com sirenomelia, falecendo quatro horas após o parto. Análises da placenta e do cordão umbilical revelaram anormalidades na implantação do feto, além de uma artéria umbilical única. Conclusão: A sirenomelia é uma anomalia congênita rara e fatal, caracterizada pela fusão das extremidades inferiores, frequentemente associada a malformações adicionais. Sua etiologia é pouco compreendida e os possíveis fatores de risco incluem diabetes materno, exposição a fármacos teratogênicos, suscetibilidade genética, infecções e idade materna. Com base no caso descrito, sugere-se que a realização de ultrassonografia é crucial para o diagnóstico precoce e tomada de decisão frente a casos de sirenomelia. No mais, a conscientização sobre a prevenção da gravidez na adolescência e o controle da glicemia em mães diabéticas são essenciais para reduzir a incidência da síndrome.
... According to this theory, sirenomelia could be considered a severe form of caudal regression [1,6]. Second hypothesis is an abnormal pattern of the vasculature. ...
... Below the origin of SUA, the aorta becomes abnormally narrow, resulting in the shunting away of blood from the hypoplastic arteries supplying kidneys, gut, and genitalia, into the SUA. This causes the diversion of blood flow to the placenta, thus resulting in defective circulation and nutrition to lower limbs causing their arrested growth [1,6]. ...
... intracytoplasmic sperm injection have also been described [1,15] Unlike in humans, the genetic basis in the animal model is well established. A sirenomelia-like phenotype in animal models has been illustrated by genetic modifications through the induction of loss-of-function mutations in bone morphogenetic protein (Bmp) or gain-of-function mutations in RA signaling [1,6]. ...
Sirenomelia also called mermaid syndrome is a congenital, rare, lethal, multisystemic human malformation of unknown etiology. The characteristic feature of sirenomelia is the fusion of the lower limbs, resulting in the appearance of a mermaid’s tail, and thus the name “mermaid syndrome.” This condition is also characterized by various severe urogenital abnormalities and the presence of a singular umbilical cord blood vessel, and it is more common in infants of diabetic mothers and in monozygotic twins. The incidence is around 1 in 60,000–70,000 pregnancies. The majority of affected fetuses are stillborn, whereas the rest of the live-born die in the early neonatal period due to complications of the gastrointestinal and urogenital systems. We are reporting a case of sirenomelia in a neonate born to an unregistered multipara mother. The baby had perinatal asphyxia, sirenomelia, dextrocardia, low set ears, lymphatic malformation, bilateral renal agenesis, absent external genitalia and anus, single umbilical artery, and congenital corneal clouding. There was no antenatal ultrasonography done and the baby died at 6 h of life.
... Sirenomelia is a rare multi-organ congenital developmental disorder in which caudal part of the fetus is abnormally developed leading to fused lower limbs. Approximate incidence is estimated to be around 1 in 60,000-70,000 pregnancies [1]. Sirenomelia is also known as mermaid syndrome due to its similarity to a fabled marine creature with head and upper body of a human female and lower half of a fish. ...
... Exceptionally, children with sirenomelia are able to survive for more than a year, mainly due to urogenital and anus surgeries. The essence of the defect is a single axial positioned lower limb, with one or two feet ( Figure 1) [48]. The bones of the lower limbs may be double or single, and it is significant only for the description/classification. ...
Abnormalities in cellular differentiation during embryo-fetal period may lead to various malformations of the spine. Caudal regression syndrome (CRS) is a group of defects with premature growth/development termination of the vertebral column. CRS can be divided into three types: sirenomelia, complete absence of the sacrum and partial absence of the sacrum. Genitourinary and gastrointestinal anomalies are common, with neurogenic bladder and bowel incontinence. Treatment of patients with CRS is complex and multidisciplinary and should be comprehensive. The most common orthopedic problems are: spinal deformity (kyphosis and scoliosis), spinopelvic instability and lower limbs deformities.
... It has seven types (I-VII) and is based on the presence or absence of the femur, tibia, and fibula. [9][10][11][12] Recurrence risk is estimated up to 3−5%. [13] Hence, genetic counseling and antenatal folic acid tablets should be advised in upcoming pregnancies. ...
A 26-year-old non-diabetic primigravida with 4 months of amenorrhea was appointed for a routine second-trimester anomaly scan. On inspection, the gravid abdominal girth of the lady did not correlate with her gestational age. Ultrasonographic examination showed a single live intrauterine gestation with anhydramnios. There was an absence of bilateral kidneys and urinary bladder with lying down adrenal sign suggestive of bilateral renal agenesis. The fetus also revealed caudal dysgenesis in the form of fusion of both lower limbs, seen as a single leg with 1 upturned foot and fused toes. There were no identifiable external genitalia and anus. The parents went ahead with medical termination of pregnancy after being informed about the condition and its incompatibility with life.
... The inferior region of the body will develop abnormally or incorrectly due to improper caudal circulation. Defective blastogenesis: between the 13th and 22nd day, it may cause the fusion of the lower part of the body, malrotation, or dysgenesis [9]. ...
Sirenomelia, also known as "mermaid syndrome" or "mermaid baby syndrome," is a very rare congenital disorder. The major anomaly in this syndrome is the fusion of the lower legs, giving it a mermaid-like appearance. This syndrome consists of a range of abnormalities affecting various systems, such as the digestive, genitourinary, and musculoskeletal systems. On the basis of the severity of the syndrome, the fetus may have a single fused bone or entirely absent bones in place of a normal pair of distinct bones. In major cases, mermaid syndrome leads to stillbirths. Its occurrence in monozygotic twins is much greater than in dizygotic twins or in a single fetus. The syndrome is believed to mainly occur in cases of maternal age less than 20 years or more than 40 years, women suffering from maternal diabetes, and prenatal exposure to retinoic acid, cocaine, and water contaminated by landfills.
A 22-year-old pregnant female was admitted with a history of amenorrhea for nine months (full-term twin pregnancy) and oligohydramnios for a caesarian section. This was the patient's second pregnancy. A cesarean section was done as instructed by the gynecologist. The patient delivered twin babies. In this twin pregnancy, the first baby was normal and healthy, while the second baby was stillborn and suffered from mermaid syndrome.
