The Potential Misdiagnosis of Multifocal Motor Neuropathy as Amyotrophic Lateral Sclerosis—A Case Series

Abstract

Multifocal motor neuropathy (MMN) is a rare neuropathy that is often treatable with immunomodulatory therapy if diagnosed early. However, accurate diagnosis is difficult due to a significant overlap of symptoms with other neurological conditions, such as amyotrophic lateral sclerosis (ALS). Evidence of immunoglobulin M (IgM) anti-ganglioside GM1 antibodies and electrodiagnostic findings of conduction block are useful diagnostic criteria for MMN but are not universal findings. This review explores the differential diagnosis of MMN and ALS and discusses three cases of MMN initially diagnosed as ALS, in which the correct diagnosis allowed effective treatment. These cases highlight the need for greater awareness of MMN among physicians.