Orofaciodigital syndrome I (OFD1; MIM 311200) is an X-linked dominant disease with lethality in males. It is characterized by facial, oral cavity and digit malformations. Typical facial and oral cavity findings include hypertelorism, broad nasal bridge, hypoplastic malar cartilage, small median cleft or pseudocleft of the upper lip, hyperplastic oral frenuli, cleft palate, bifid or lobulated tongue, lingual hamartomas, and hypodontia. Hand malformations consist of brachydactyly, syndactyly, clinodactyly, and occasionally polydactyly. Approximately 50% of the patients have polycystic kidneys. Fibrocystic disease of the liver and pancreas can be present. Central nervous system malformations are variable and found in about 40% of the patients. OFD1 is caused by mutations in the OFD1 gene, which codes for oral-facial-digital syndrome 1 protein. Mutations in this gene can also cause Simpson-Golabi-Behmel syndrome, type 2 (SGBS2; MIM 300209) and Joubert syndrome 10 (JBTS10; MIM 300804).