Congenital unilateral muscle hyperplasia of the hand with ulnar deviation of the fingers.

Three cases of congenital unilateral muscular hyperplasia of the hand combined with ulnar deviation of the fingers are presented. In all three patients the deformity was confined to the right upper extremity, and there were no other associated congenital malformations. All patients displayed anomalous or hyperplastic musculature acting on the proximal phalanges of the fingers, contributing to the associated ulnar drift of the hand. This condition is previously unreported, and is a different entity from the previously described "windblown hand".