Multifocal motor neuropathy (MMN) is a progressively worsening condition where muscles in the extremities gradually weaken.
The disorder, a pure motor neuropathy syndrome, is sometimes mistaken for amyotrophic lateral sclerosis (ALS) because of the similarity in the clinical picture, especially if muscle fasciculations are present.
Many patients, once undergoing treatment, only experience mild symptoms over prolonged periods, though the condition remains slowly progressive.
[2] MMN is thought to be caused by alterations in the immune system, such that certain proteins (antibodies) that would normally protect one from viruses and bacteria begin to attack constituents of peripheral nerves.
More recent studies also suggest that newer tests for antibodies directed against GM-1, as well as a number of related gangliosides, are positive in over 80% of MMN patients.
These criteria are designed to differentiate the disorder from ALS (purely motor but with UMN signs), the Lewis-Sumner Syndrome variant of Chronic inflammatory demyelinating polyneuropathy (CIDP) (similar to MMN but usually with significant sensory loss), and "vasculitis" (a type of multiple mononeuropathy syndrome caused by inflammatory damage to the blood vessels in nerves that also causes sensory and motor symptoms).
[citation needed] Multifocal motor neuropathy is normally treated by receiving intravenous immunoglobulin (IVIG), which can in many cases be highly effective, or immunosuppressive therapy with cyclophosphamide or rituximab.
[4] Ongoing specialist community support, information, advice, and guidance is available from a range of Charities, Non-Government Organisations (NGOs), and Patient Advisory Groups around the world.