Muscle overgrowth of the upper limb in a proximo-distal gradient and concurrent hypoplasia of the index finger.

BACKGROUND: There are many forms of congenital overgrowth of the upper limb. We aim to present the characteristics of a new form overgrowth of the upper limb.
METHODS: This is a case series of 3 sporadic cases from 3 different Saudi Arabian families with progressive overgrowth of one or both upper limbs. The literature is reviewed for similar cases.
RESULTS: The 3 cases were considered unique because they had almost identical clinical features as follows: the progressive overgrowth only affected the muscles (and not bones or other soft tissues); the palm was wide with abnormal dermatoglyphics; the space between the second and third metacarpals was wide resulting in radial deviation of the index finger metacarpal, the index finger was mildly hypoplastic, and the metacarpophalangeal joint of the thumb had a hyperextension deformity. Ulnar deviation of the fingers was not a constant feature. When the literature was reviewed, similar cases were found, but they were mostly discussed as an unusual form of windblown hand deformity because of the ulnar deviation of the fingers.
CONCLUSION: The author believes that these cases present a new clinical form of overgrowth of the upper limb. LEVEL OF EVIDENCE: Level IV (case series).