To comment on this article Introduction Polydactyly is defined as duplication of a finger or part of it. Sporadic as well as familial occurrence have been described. In the latter it is usually inherited as an autosomal dominant trait. In general, polydactyly is one of the most frequent congenital anomalies. According to location it can be subdivided into pre- and postaxial polydactyly.
Preaxial forms are less common than postaxial forms.
Negroes have a ten times higher rate of postaxial polydactyly compared to Caucasians. Polydactyly occurs in a broad variety of phenotypes. This causes great difficulties in developing an adequate classification system. Group I to VI define biphalangeal duplications of the thumb at different levels. The genetic defects underlying the majority of congenital hand malformations are unknown.