Macrodactyly and localized hypertrophic neuropathy.

Abstract

A case of focal hypertrophic neuropathy involving the left median nerve associated with macrodactyly of the left thumb is reported. The pathologic picture showed classic onion bulb formation caused by proliferation of Schwann cell processes, collagen, and fibroblasts. An unusual feature of the ultrastructural aspects of the disorder, to our knowledge not previously recognized, was the participation of processes from one Schwann cell in the formation of several onion bulbs. Although the relationship of the focal hypertrophic neuropathy to the macrodactyly remains speculative, it is tentatively attributed to disturbed trophic functions of peripheral nerves. Onion bulb formation, although not usually clinically apparent at birth, might arise in utero, since the macrodactyly in our patient was noted in infancy.