[Sirenomelia].

Sirenomelia is an uncommon congenital malformation of unknown etiology characterized by all degrees of severity in merning, malrotation, and dysgenesis of the lower limbs, combining as it does malformation with several anomalies of the external and internal organs, specially of the urogenital and gastrointestinal systems and other lumbosacral vertebral abnormalities; the severity of the associated malformations are not compatible with life. A genetic mechanism leading to sirenomelia is unlikely, due to the absence of the familial cases.