[Polyneuropathies and gammapathies: a form with antiglycoprotein MAG antibodies].

Two cases of polyneuropathy with IgM gammopathy are reported. Myelin associated glycoprotein is the antigen for the monoclonal antibody in both of these patients. The same antigenic specificity has now been identified in other patients having a paraproteinemia with a polyneuropathy. These findings suggest the existence of a new syndrome characterized by: a) a primary demyelinating neuropathy; b) a monoclonal IgM antibody to a specific glycoprotein component of myelin, referred to as myelin associated glycoprotein (MAG). As in other humorally mediated autoimmune diseases, it is suggested that demyelination is caused by circulating anti-MAG antibodies. The role of immunosuppressive drugs and plasmapheresis is discussed.