MYCN and Feingold syndrome type 1: Feingold syndrome, caused by NMYC mutations–a member of the MYC family of oncogenes, is characterized by syndactyly of toes 2–3 and 4–5, hypoplastic middle phalanges, and other systemic abnormalities.[26, 27] Conditional NMYC inactivation in mice results in skeletal and joint abnormalities, implicating NMYC in interdigital cell death and joint formation, linking its dysfunction to syndactyly and brachydactyly.[28]