Sirenomelia

Sirenomelia
Sirenomelia, Lyon natural history and anatomy museum
SpecialtyMedical genetics 
SymptomsFused legs
ComplicationsMalformations of organs
Usual onsetBirth
CausesSee Causes
Risk factors?
TreatmentSurgery
PrognosisUsually die in infancy
Deaths?

Sirenomelia, also called mermaid syndrome, is a rare congenital deformity in which the legs are fused together, giving the appearance of a mermaid's tail, hence the nickname.