[Peripheral hereditary neuropathies: Charcot-Marie-Tooth types 1 and 2]

We report 14 cases of patients with Charcot-Marie-Tooth types 1 (CMT) and type 2 (CMT2). The objective of this study was to determine the diagnostic value of structural studies of peripheral nerve and striated muscle biopsies and to discuss correlations with clinical symptoms and electrophysiologic findings.

Nerve and muscle biopsies were obtained and processed according to standards methods for transmission electron microscopy. Diagnosis of CMT was based on clinical electrophysiologic findings.

Our results demonstrated that myelinated fibers showed moderate-to- severe demyelinization and remyelinization, folding complex, tomacula formations, and presence of moderate vacuoles into myelin. The axonal cytoskeleton shows an important decrease of neurofilaments and microtubules in myelinated and unmyelinated nerves. Striated muscle showed different degenerative changes in Z disc. One important finding was presence of crystals inclusions in mitochondrion. In 11 cases, it was possible to find relevant changes in mitochondria-like hyperplasia. In this study, we had four cases with > 20 years of evolution; these cases showed relevant degenerative changes in nerve and muscle. Nerves presented great demyelination with damage in cytoskeleton of the axon, while fibers of muscle had necrosis and hyalinization.

According to our results, it is possible to distinguish morphologically CMT subtypes, due to the fact that in CMT2 we found a 50% decrease of filaments and microtubules that were reduced in myelinic axons; this finding does not occur in CMT1.