A congenital anomaly characterized by the presence of supernumerary fingers or toes.

A thumb with three phalanges in a single, proximo-distal axis. Thus, this term applies if the thumb has an accessory phalanx, leading to a digit like appearance of the thumb.

This syndrome has manifestation of symmetric, nonopposable triphalangeal thumbs and radial hypoplasia. It has been described in eight patients (five females and three males) spanning generations of a family. The affected males also presented with hypospadias. The syndrome is inherited as an autosomal dominant trait.