Sirenomelia, also called mermaid syndrome, is a rare congenital deformity in which the legs are fused together, giving the appearance of a mermaids tail, hence the nickname. Classification
Sirenomelia is classified by the skeletal structure of the lower limb, ranging from class I, where all bones are present and only the soft tissues are fused, to class VII where the only bone present is a fused femur.It has also been classified as an expanded part of the VACTERL association and as a form of caudal regression syndrome. Presentation
Sirenomelia is mainly characterized by the fusion of both legs with rotation of the fibula. It may include the absence of the lower spine, as well as abnormalities of the pelvis and renal organs. It was previously thought to be a severe form of sacral agensis/caudal regression syndrome, but more recent research confirms that these two conditions are not related. NORD has a separate report on caudal regression syndrome. In general, the more severe cases of limb fusion correlate with more severe dysplasia in the pelvis. Rather than the two iliac arteries present in fetuses with complete renal agenesis, fetuses with sirenomelia display no branching of the abdominal aorta, which is always absent.Associated defects recorded in cases of sirenomelia include neural tube defects (rachischisis, anencephaly, and spina bifida), holoprosencephaly, hypoplastic left heart syndrome, other heart defects, esophageal atresia, omphalocele, intestinal malrotation, persistent cloaca, and other limb defects (most commonly absence of the radius). Causes
The ultimate cause of sirenomelia is a subject of debate.
For the developmental symptoms, Educational intervention and speech therapy beginning in infancy could help to reduce the high risk for motor, cognitive, speech, and language delay. For the skeletal features, referral to an orthopedist for consideration of surgical release of contractures. In addition, early referral to physical therapy could help increase joint mobility. Lastly, thyroid hormone replacement could help out the thyroid dysfunction. History
In 1988, Goldblatt et al. first reported a 4-year-old boy with hypoplastic patellae, mental retardation, scrotal hypoplasia, skeletal deformities, kidney anomalies, flattened nasal bridge, and short stature. Later in 2000, Cormier-Daire et al. reported seven patients with genital anomalies (scrotal hypoplasia and cryptorchidism in the boys and clitoral hypertrophy in the girls), facial dysmorphism, kidney anomalies, absent patellae, and severe mental retardation in the two survivors. The condition is now known as genitopatellar syndrome. See also
Say-Barber-Biesecker-Young-Simpson syndrome
KAT6B

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