Anti-myelin-associated glycoprotein neuropathy

Abstract

The anti-myelin-associated glycoprotein (MAG) neuropathy is an antibody-mediated demyelinating neuropathy. The clinical picture is characterized by a distal and symmetric, mostly sensory neuropathy. Monoclonal immunoglobulin M anti-MAG antibodies are uniquely found in this condition and are believed to be pathogenic. This review focuses on recent progress in understanding the mechanisms of this neuropathy and discusses new therapeutic advances. Different electrophysiological parameters have been demonstrated to distinguish the anti-MAG-associated polyneuropathy from chronic inflammatory demyelinating polyneuropathy. The electrophysiological findings generally indicate a predominantly demyelinating neuropathy with a distal accentuation of conduction slowing. Analyses of pathology in nerve tissue from anti-MAG patients using classical nerve biopsy or skin biopsy tissue demonstrated immunoglobulin M deposits at the site of MAG localization, demyelination and axonal degeneration. MAG is a Schwann cell-based glycoprotein and has been implicated as a mediator of an outside-in signaling cascade influencing the cytoskeletal integrity of axons. Therapy in patients with anti-MAG neuropathy is directed at reducing the antibody concentration, blocking the effector mechanisms and depleting the monoclonal B cells. The recent availability of rituximab, a monoclonal antibody suppressing B-cell clones, which is not myelosuppressive and does not cause secondary malignancies, allows for early targeted intervention.