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.

Monozygotic twins discordant for pediatric trigger-locked thumbs

“…While much has been discussed about the pathophysiology of the congenital trigger thumb, the debate continues about its cause: a genetic versus acquired etiology. Some studies in the literature lean towards a genetic cause for the condition [3,[8][9][10][11], whereas others argue that it may be acquired in nature [12,13]. Regardless of the true cause of the condition, it is possible that some children are born with the condition but it manifests later in infancy or childhood.…”

“…The few articles available in the literature on this topic suggest that genetic factors are important in its etiology [5-8, 10, 11]. There are three case reports of "congenital trigger thumb" in twins [3,4,8] that support the genetic factors in the etiology of the condition. These reports are based on the fact that the condition occurred in "identical" twins but without a proof of the monozygotic nature of the twins with DNA analysis.…”

Congenital trigger thumb in children

“…Several authors have suggested a possible congenital predisposition, based on the observation that the lesion is sometimes present at birth [2,[9][10][11][12][13] or shortly afterwards, along with a high incidence of bilateral occurrence in children and the occurrence in monozygotic twins [11,14,15]. Some authors believe that CTT is familial [12,16].…”

Serial Ultrasound Evaluation of Pediatric Trigger Thumb

“…Its incidence within the first year of life (3.3/ 1000) exceeds that of both clubfoot and developmental dysplasia of the hip. [9][10][11][12][13][14] Thickening and hypervascularization of the A1 pulley are the hallmarks of trigger fingers on sonography in adults. 2,3 Proposed etiologies include trauma, infection, congenital soft-tissue malformation, intratendinous nodules, or articular malformation.…”