Summitt syndrome is an extremely rare disorder originally described in two brothers and characterized by mild to severe craniosynostosis and syndactyly, obesity, and normal intelligence. Acrocephaly, brachydactyly, clinodactyly, mild syndactyly of the hands and feet, genu valgum and marked obesity were later described in another patient. There have been no further descriptions in the literature since 1979. Summitt syndrome could be a variant of Carpenter syndrome.

Webbing or fusion of the fingers or toes, involving soft parts only or including bone structure. Bony fusions are referred to as \"bony\" syndactyly if the fusion occurs in a radio-ulnar axis. Fusions of bones of the fingers or toes in a proximo-distal axis are referred to as \"symphalangism\".