Transverse deficiency of the hand in one of monozygotic twins.

In this paper, we report on one male infant of twins with a left hand anomaly. The hand deformities were diagnosed as so called "congenital amputation" which is a synonym of "transverse deficiency" in Swanson's classification. The left hand showed spontaneous amputation at the level of the palm. There were two rudimentary digits on the stump, and an extremely hypoplastic thumb and little finger. The other twin had no anomaly. The results of laboratory findings on blood groups and HLA types suggest that these twins are monozygotic. From these facts, we considered that environmental factors are more important than genetic ones in the pathogenesis of transverse deficiency and symbrachydactyly of the hand.