Radiologic findings of the flexor pollicis longus hypoplasia.

A case of a 10-year-old boy with hypoplasia of the flexor pollicis longus and without other associated anomalies and trauma history is reported. Flexor pollicis longus tendon anomalies are rare; several types of this congenital anomaly have been reported in the literature. The diagnosis should be considered to the conditions of a patient who was unable to flex the interphalangeal joint of the thumb. Hypoplastic thumb or absent interphalangeal joint crease may be a diagnostic feature in such cases. We preoperatively present the radiological findings of this rare congenital anomaly. Ultrasound and magnetic resonance imaging (MRI) features have never been reported in the literature.