A Novel Duplication Mutation in the Myelin Protein Zero Gene Causing Mild, Nonprogressive Demyelinating Neuropathy

Mutations in the myelin protein zero (MPZ) gene can cause a variety of clinical and electrophysiological forms of genetic neuropathies including Charcot-Marie-Tooth (CMT) type 1B disease which is characterized by demyelinating features. We present a father and daughter with neuropathy carrying a novel 31 base pair duplication mutation in the 5' untranslated region of the MPZ gene, c.-23_8dup31. Genetic analysis and protein modeling indicated that this is a frameshift mutation resulting in premature truncation of the encoded protein. The daughter underwent repeat neurological examination and electromyography testing over an 11-year time span demonstrating no clinical or electrophysiological change. Our study expands the clinical and genetic spectrum of mutations that can cause CMT type 1B disease and demonstrates the value of sequence analysis of noncoding portions of a gene that are not intronic.