[Congenital neuropathy caused by hypomyelination].

A 9 year-old girl with congenital hypomyelination neuropathy is reported. Clinical features were delayed motor development, disturbances of gait, deep sensory defect, areflexia and mild distal palsy with claw feet. E.M.G. revealed dramatically diminished motor conduction velocities. C.S.F. protein was normal. Histological examination of the right sural nerve revealed a severe loss of myelinated fibers. On electron microscopy, poorly myelinated and large amyelinated axons were enclosed by normal Schwann cells and surrounded by multiple single or double layered basement membranes which were concentrically arranged in an onion bulb pattern. This case of congenital hypomyelination neuropathy is compared with ten similar cases in the literature.