Preaxial polydactyly of fingers (Q93800)

Preaxial polydactyly of fingers is a limb malformation syndrome characterised by the attachment of a superfluous digit on the first digit. Four types have been defined. Type I (polydactyly of biphalangeal thumb): duplication of one or more skeletal components of a biphalangeal thumb; type II (polydactyly of triphalangeal thumb): presence of a usually opposable triphalangeal thumb which may or may not be duplicated; type III (polydactyly of index): thumb replaced by one or two triphalangeal digits with index dermatoglyphic pattern; type IV (polysyndactyly): variably mild degrees of thumb duplication and variable 3-4 syndactyly.