Hereditary motor and sensory neuropathy type I: clinical and neurographical features of the 17p duplication subtype.

Forty-four affected individuals, aged 8-68 years (mean 34 years), from six families with hereditary motor and sensory neuropathy type I (HMSN I, Charcot-Marie-Tooth disease type 1) were investigated to determine the clinical and electroneurographical characteristics of the HMSN I subtype that is defined by the presence of a DNA duplication on chromosome 17p. Motor nerve conduction velocity (MNCV) and, to a lesser extent, compound muscle action potential amplitude, were inversely related to clinical severity. Neither clinical severity nor MNCV were significantly related to age. These results suggest that the primary pathological process is not, or only slightly active after childhood.