Dorsal dimelia of the index finger in a patient with absent thumb and radial club hand.

Dorsal dimelia is a rare form of duplication along the dorsoventral axis as opposed to polydactyly and hyperphalangism, which are duplications along the radioulnar and proximodistal axes, respectively. All previous cases of dorsal dimelia involved the ulnar digits. We report the first human case of dorsal dimelia of a radial digit (index finger) in a patient with absent thumb and radial club hand. Associated anomalies of previously reported cases of dorsal dimelia are reviewed and their pathogenesis is discussed.