familial caudal dysgenesis sirenomelia https://www.malacards.org/card/sirenomelia icd11.foundation:473306797 MEDGEN:52357 Sirenomelus Fused legs and feet mermaid syndrome SCTID:67254002 Orphanet:3169 symmelia mermaid malformation MedDRA:10049216 MONDO:0017850 sirenomelia sequence NORD:1720 NCIT:C118455 Sirenomelia is a rare, genetic, developmental defect during embryogenesis disorder characterized by fusion of the lower limbs and associated with some degree of lower extremity reduction and persistent vitelline artery. Patients also present severe malformations of the musculoskeletal system (e.g. sacral agenesis), as well as the urogenital and lower gastrointestinal tracts (e.g. renal agenesis, absent bladder, rectal/anal atresia, and absent internal genitalia). Most cases are stillborn, or die during, or shortly after, birth. UMLS:C0037205 GARD:0007652