Pediatric trigger thumb in identical twins: congenital or acquired?

Abstract

Pediatric trigger thumb is an uncommon condition with a calculated incidence of 3 per 1000 live births or less. Some reports have suggested a congenital etiology while others could not find a single case of pediatric trigger thumb at birth. This article reports the occurrence of bilateral trigger thumbs in identical twins, age 3 years and 9 months, affecting their thumbs to similar extents, which may suggest a congenital etiology.Congenital etiology for trigger thumb has been proposed for many reasons: occurrence in infants, occurrence in twins, occasional bilaterality, possible presence of triggering at birth, and absence of history of trauma. The occurrence of pediatric trigger thumb in twins has been reported 3 times in the literature; all reported cases were bilateral, as in our case.The mean age at presentation of pediatric trigger thumb is 2 years. The thumb is usually held in a fixed flexion position (mimicking a fracture). Examination usually reveals a palpable nodule in the flexor pollicis longus tendon at the metacarpal joint. This is an important clinical sign. Triggering in children, however, is rare. Macroscopically, there is a nodular thickening of the tendon itself. Pathological changes can be found in the tendon, tendon sheath, or both. A specimen taken from one of the nodules in our case showed degenerative changes while those from both pulleys were normal.Pediatric trigger thumb responds predictably to A1 pulley release, preferably before age 4 years, although milder cases may resolve spontaneously.