Congenital absence of the flexor pollicis longus--a case report.

Congenital absence of the flexor pollicis longus, associated with hypoplasia of the thumb, is an unusual anomaly. A case of congenital absence of the flexor pollicis longus without hypoplasia or aplasia of the thumb and thenar muscles, which is described, is very rare. Surgical treatment for the transfer of the ring finger flexor superficialis tendon to provide the thumb interphalangeal joint with flexion resulted in a significant improvement in pinch.