Mondo Description Any hydrolethalus syndrome in which the cause of the disease is a mutation in the HYLS1 gene.

Uniprot Description A lethal syndrome characterized by polydactyly, central nervous system malformation, and hydrocephalus. The polydactyly is postaxial in the hands and preaxial in the feet. A highly characteristic hallux duplex is seen in almost no other situation. In half of the cases, a large atrioventricular communis defect of the heart is found. The pregnancy is characterized by hydramnios, which is often massive, and by preterm delivery.