Peripheral neuropathy and monoclonal IgM with antibody activity against peripheral nerve myelin; effect of plasma exchange.

Serum IgM antibodies directed against peripheral nerve myelin were demonstrated using enzyme-linked immunosorbent assay, mixed haemagglutination and indirect immunofluorescence in 3 patients with chronic polyneuropathy and monoclonal serum IgM. Isoelectric focusing followed by antigen immunofixation and autoradiography showed that the antimyelin antibodies co-migrated with the monoclonal IgM. Plasma exchange alone, without chemotherapy, proved beneficial in 2 patients. In one patient, plasma exchange was discontinued because of low IgG levels. Serum IgM and antimyelin antibodies decreased during plasma exchange and no increase beyond initial levels was noted after cessation of treatment.