Proposal of New Category for Congenital Unilateral Upper Limb Muscular Hypertrophy

Abstract

According to congenital anomalies of the hand and forearm classifications, the common characteristic of overgrowth problems is the skeletal overgrowth of part or all of the hand. Congenital unilateral muscular hypertrophy of the upper extremity has been classified under the overgrowth (gigantism) problems as whole-limb hemihypertrophy. The common characteristic of overgrowth problems is the skeletal overgrowth of part or all of the hand, which is not prominent in these patients. Only 15 cases with this anomaly have been reported since 1962. These patients have abnormal muscles with hypertrophic appearance and changed tendon to muscle length ratio. This type of muscular hypertrophy shows an increase in the number of fibers in transverse section, as also seen in multiply innervated muscles like the sartorius and gracilis in humans. Although this phenomenon has a mosaic type distribution, there is no progression of the muscular hypertrophy during growth period. Hand deformities are not due to a part of progression of the disease but result of imbalance of the extrinsic and intrinsic muscles. The evolutionary changes of skeletal muscles should be investigated to explain this congenital phenomenon and might be classified in a different entity from the present categories.

Early activating somatic PIK3CA mutations promote ectopic muscle development and upper limb overgrowth

“…2 The umbrella term PIK3CA-related overgrowth spectrum (PROS) is a heterogeneous group of rare genetic disorders with overgrowth caused by somatic mosaic PIK3CA mutations. 6 The etiology remains still undetermined but it has recently been reported that isolated congenital muscular upper limb overgrowth can be related to somatic mosaic PIK3CA mutations. 4 The terminology "aberrant muscle syndrome" or "accessory muscle syndrome" has been suggested to describe patients with "hypertrophy of the hand and arm because of aberrant muscles with or without hypertrophy of the muscles."…”

“…5 It has been proposed that an increased number of neuromuscular junctions and a change in the muscle-tendon ratio is involved in muscle hypertrophy development. 6 The etiology remains still undetermined but it has recently been reported that isolated congenital muscular upper limb overgrowth can be related to somatic mosaic PIK3CA mutations. 7,8 Somatic activating PIK3CA mutations are common in at least 12 different cancer types.…”

Congenital Unilateral Upper Limb Muscular Hypertrophy Associated With Contracture of an Extrinsic Extensor Tendon

“…These and other authors agree that the joint deformities progress with growth (Lanz et al, 1994;So, 1992;Tanabe et al, 1997). Takka et al (2005) noted no radiographic bony deformity in a neonatal case, but spreading of the metacarpal bones, presumably as a result of the increasing size of the hypertrophied intrinsic muscles, after 3 years of follow-up. In this case, a hypertrophied extensor indicis proprius with reduced excursion of its tendon caused a difficulty of flexion of the index finger in a manner similar to our case.…”

Upper limb muscle overgrowth with hypoplasia of the index finger: a new over-growth syndrome caused by the somatic PIK3CA mutation c.3140A>G

“…Upon reviewing the English literature prior to Al-Qattan [2] report, several similar cases were found in the Hand Surgery literature [4–9]. These hand surgeons commented on the muscle hypertrophy of the upper limbs as well as the aberrant muscles and the deviation of the fingers.…”