Mutations in the ganglioside-induced differentiation-associated protein 1 gene 
cause either autosomal recessive demyelinating Charcot-Marie-Tooth disease type 
4A or autosomal recessive axonal Charcot-Marie-Tooth disease with vocal cord 
paresis. We sequenced the ganglioside-induced differentiation-associated protein 
1 gene in 138 patients from 119 unrelated families diagnosed with either 
demyelinating or axonal autosomal recessive Charcot-Marie-Tooth disease. We 
detected six distinct mutant alleles in four families, four of which are novel. 
Electrophysiological studies show severely slowed motor nerve conduction 
velocities with severely reduced compound muscle action potentials. However, one 
patient had a normal conduction velocity in the ulnar nerve. Based on the 
electrophysiological tests, patients with ganglioside-induced 
differentiation-associated protein 1 mutations will therefore be classified as 
either axonal or demyelinating Charcot-Marie-Tooth disease. The 
neuropathological aspect shows a divergent pattern; nerve biopsies taken from 
two siblings at the same age and sharing the same ganglioside-induced 
differentiation-associated protein 1 gene mutation showed a dissimilar severity 
stage.