For a general phenotypic description and a discussion of genetic heterogeneity of Charcot-Marie-Tooth disease type 1 (, see CMT1B (118200).

CMT1A is the most common form of CMT. The average age of onset of clinical symptoms is 12.2 +/- 7.3 years. Slow nerve conduction velocity (NCV) less than 38 m/s is highly diagnostic and is a 100% penetrant phenotype independent of age (Lupski et al. (19911992)).