[The nosological situation of hereditary motor and sensory neuropathies (HMSN, Charcot-Marie-Tooth disease, neural muscular atrophy)].

Hereditary motor and sensory neuropathies (HMSN) comprise a heterogeneous group of disorders. Since phenotypic manifestations are similar in most families, classification is based on differences in the mode of inheritance, onset and progression of the disease, nerve conduction velocity and nerve biopsy findings. Autosomal dominant, autosomal recessive, X-dominant and X-recessive forms, substantial intrafamilial differences, intermediate forms and the combination of neuropathies with spinocerebellar degeneration within one and the same sibship have been described. On the basis of selected own cases it is demonstrated that there is a broad spectrum of functional and structural abnormalities depending on the progression of the disease and on the site of nerve studied (proximal or distal part). Both the neuronal and hypertrophic variants begin with axonal degeneration of the dying back type followed by segmental demyelination and variable degrees of hypertrophic Schwann cell proliferation. Constantly, posterior columns of the spinal cord reveal fiber loss. Since the molecular basis of the different forms remains to be clarified it seems to be of greater interest to underline common features than to separate seemingly different nosological entities. It is suggested that the latter are partly the result of a selection of cases with a variable severity. Evidently, the syndrome of myatrophic ataxia comprises apart from "pure" HMSN with unsignificant degenerations of posterior columns and "pure" Friedreich's ataxia with mild peripheral nerve fiber loss intermediate forms.