Polydactyly is defined as duplication of a finger or part of it. It occurs as an isolated malformation, in association with other malformations of the hands and/or feet, or as a part of a syndrome. Sporadic as well as familial occurrence have been described. In the latter it is usually inherited as an autosomal dominant trait. The prevalence of polydactyly with or without an associated malformation varies between 5 and 17 per 10,000 live births.
Types
central polydactyly (medial ray)
postaxial polydactyly (lateral ray)
Etiology
isolated polydactyly (postaxial hexadactyly ++)
syndromal polydactyly (in malformative syndromes)
References
Lettice LA, Hill RE. Preaxial polydactyly: a model for defective long-range regulation in congenital abnormalities. Curr Opin Genet Dev. 2005 Jun;15(3):294-300. PMID: #15917205#