[Hereditary motor and sensory neuropathy (Charcot-Marie-Tooth disease). Molecular-genetic aspects].

Hereditary motor and sensory neuropathy (HMSN) comprises a heterogenous group of peripheral neuropathies which are classified on the basis of symptoms, mode of inheritance and electrophysiological and neuropathological investigations. HMSN type I, or Charcot-Marie-Tooth disease (CMT) type 1, is a hypertrophic and demyelinating neuropathy with reduced nerve conduction velocity, and most often with dominant inheritance. HMSN type II (CMT type 2), the neuronal or axonal form, is dominantly inherited with normal or only moderately reduced nerve conduction velocity. HMSN type III, also called Déjérine-Sottas disease, is a hypertrophic neuropathy with markedly reduced nerve conduction velocity. HMSN type I is genetically heterogenous with at least four autosomal loci and at least two X-linked loci. The most frequent form, HMSN type Ia, is associated with a specific duplication on chromosome 17, which can be detected by DNA-analysis. The genes for HMSN type Ia, Ib and an X-linked dominant form have been identified as PMP22, MPZ and GJB1 respectively. Analysis for these molecular defects will become important in the differential diagnosis of peripheral neuropathies and will surely prove invaluable in the genetic counselling of the families.