[A case of IgM paraproteinemic polyneuropathy complicated with serum anti-myelin-associated glycoprotein and anti-GM1 antibodies].

A 57-year-old man was admitted to our hospital complaining of slowly progressive numbness over the hands and legs. Neurological examinations revealed marked loss of superficial sensation of glove-stocking type, mild distal weakness over the extremities and diffuse hyporeflexia. Laboratory examinations disclosed marked increase of serum IgM level and significantly increased kappa-light chain of IgM immunoelectrophoresis. Bone marrow aspiration showed no evidence of malignancy. Motor and sensory nerve conduction velocities were decreased. Sural nerve biopsy was characterized by marked loss of large myelinated fibers, onion bulb formation and widely spaced major dense lines of myelin. The immunological examinations revealed two different antibody activities of IgM against myelin-associated glycoprotein (MAG) and GM1 in serum. Treatment with prednisolone (PSL) 60 mg daily did not improve his neurologic signs and symptoms. Then double-filtration plasmapheresis was performed, which improved the neurologic symptoms and decreased both anti-MAG and anti-GM1 antibody titers. This is the first Japanese case presenting IgM paraproteinemic polyneuropathy with simultaneous occurrence of anti-MAG and anti-GM1 antibodies.