Two cases of congenital hypomyelination neuropathy.

The clinical features and findings in biopsied sural nerves of two cases of congenital hypomyelination neuropathy were reported. Case 1 had slightly retarded motor milestones without evidence of respiratory distress during the neonatal period. Case 2 had difficulty in swallowing and respiration after birth and severely delayed motor milestones. The sural nerve, on light microscopy, revealed reduced density of myelinated fibers in the two cases. Electron microscopy disclosed hypomyelination without evidence of active demyelination or axonal changes in the two cases. Onion-bulbs were composed of concentric whorls of Schwann cell process surrounding particularly small myelinated fibers in case 1 and of concentric lamellae, mainly consisting of two parallel layers of basement membrane, in case 2. Congenital hypomyelination neuropathy shows variability of clinical features such as in our two cases. We suspected that there was gradation of severity both in clinical expression and in the disorder of Schwann cells.