Ultrastructural and cytochemical observations in a case of dominantly inherited hypertrophic (Charcot-Marie-Tooth) neuropathy.

Ultrastructural and cytochemical studies were carried out on the sural nerve of a 6 1/2 year old girl with dominantly inherited hypertrophic (Charcot-Marie-Tooth) neuropathy. Electron microscopy revealed a paucity of myelinated fibers, with inappropriately thin myelin sheaths and onion-bulb formations associated with those fibers that were myelinated. In some cases the nodal axolemma was folded so as to form irregular excrescences. At other nodes, the non-myelinated gap was enlarged. Following staining with ferric ion and ferrocyanide, dense precipitates were observed on the cytoplasmic surface of the axolemma at some nodes of Ranvier, as in normal peripheral axons. At other nodes, staining was attenuated or absent. The latter result is similar to our findings in the dy/dy dystrophic mouse. These results are consistent with the hypothesis that, in dominantly inherited hypertrophic neuropathy, there are abnormalities of structure of the axolemma, in addition to an abnormality of the myelin sheath.