Charcot-Marie-Tooth Disease, Type 1A

Abstract

Peroneal muscular atrophy, or Charcot-Marie-Tooth disease, is characterized by a wide genetic heterogeneity, including forms with both autosomal dominant and recessive or X-linked pattern of inheritance (Tables 70.1 and 70.2). Electrophysiological studies suggested that the slowing of nerve conduction velocities distinguishes patients with a hypertrophic demyelinating form (CMT type 1) from patients with a neuronal form (CMT type 2). CMT1A is the most common form of CMT. The onset of symptoms occurs in average around 12 years. Slow nerve conduction velocity less than 38 m/s is highly diagnostic and is a fully penetrant phenotype independent of age. The basis of the disease is usually a duplication in the PMP22 gene, which encodes the peripheral myelin protein 22. PMP22 comprises 2–5 % of peripheral nervous system myelin (produced primarily by Schwann cells).