Axonal neuropathy due to myelin protein zero mutation misdiagnosed as amyloid neuropathy.

In up to 50% of chronic idiopathic axonal neuropathies, an underlying diagnosis may be identified, including hereditary neuropathy. Charcot-Marie-Tooth disease (CMT) is clinically and genetically heterogeneous. Several mutations in the myelin protein zero (MPZ) gene have been associated with different CMT phenotypes, including classical demyelinating CMT1B and the axonal form of the disease. Primary amyloidosis, a rare disease where the amyloid is formed by the N-terminal portion of a monoclonal immunoglobulin light chain, may be complicated by polyneuropathy. We report a patient who was incorrectly diagnosed with amyloid neuropathy, but was found to have axonal CMT1B only after sural nerve biopsy ruled out an acquired amyloid neuropathy.