Dominantly inherited motor and sensory neuropathy type I. Genetic, clinical, electrophysiological and pathological features in four families.

This report describes the genetic, clinical, electrophysiological and sural nerve biopsy features in 26 affected members and 21 unaffected relatives from 4 families with autosomal dominant inherited motor and sensory neuropathy (HMSN), Type I. In all age categories, the proportion of affected to unaffected individuals at risk did not significantly differ from the expected 50%. The peak age of onset was in the first decade. There was a complete concordance between nerve conduction velocity in the propositi and that in their affected relatives within each family. Marked slowing of conduction velocities was present as early as the age of 2.5 years, while precocious clinical signs and symptoms were quite subtle. Determination of conduction velocity is a valuable aid aid to the early diagnosis of the disease.