[Hereditary Polyneuropathies].

Hereditary neuropathies are a group of diseases of which the most prevalent is Charcot Marie Tooth disease (CMT). From the clinical point of view pes cavus is a typical yet not specific sign for CMT. Motor signs like bilateral foot drop are dominant over sensory signs. Mutations in some 80 genes can lead to CMT. Whereas clinical sign can hardly differentiate between these genotypes, there is a clear differentiation by classical neurography: median nerve conduction velocity of less or more than 38 m / s differentiates between CMT type 1 and CMT type 2. The two most common forms are CMT1A induced by duplication of the PMP22 gene and hereditary neuropathy with liability to pressure palsy (HNPP) induced by deletion of the PMP22 gene.