Holoprosencephaly-caudal dysgenesis syndrome is a central nervous system malformation syndrome characterized by holoprosencephaly with microcephaly, abnormal eye morphology (hypotelorism, cyclopia, exophthalmos), nasal anomalies (single nostril or absent nose), and cleft lip/palate, combined with signs of caudal regression (sacral agenesis, sirenomelia with absent external genitalia).

Wrist is bent inward toward the thumb because of a congenital defect associated with shortening or absence of the radius.