Congenital Hypomyelinating Neuropathy Attributable to a De Novo p.Asp61Asn Mutation of the Myelin Protein Zero Gene

We describe a boy aged 2 years and 11 months with congenital hypomyelinating neuropathy attributable to a de novo heterozygous missense mutation of c.181G>A (p.Asp61Asn) in the myelin protein zero gene. A nerve conduction study indicated markedly reduced motor conduction velocities in the upper and lower extremities. Stimuli of up to 50-100 mA were necessary for nerve activation, suggesting diseased nerves with greatly decreased excitability. A sural nerve biopsy revealed a marked loss of large myelinated fibers, the absence of myelin breakdown products, occasional basal lamina onion-bulb formations, and tomacula-like structures. The p.Asp61Asn mutation is novel in congenital hypomyelinating neuropathy, but was previously reported in a patient with Charcot-Marie-Tooth disease type 1.