Monoclonal IgM gammopathy with anti-myelin associated glycoprotein (MAG) activity and polyneuropathy. A study of three cases.

The authors describe three patients with a chronic sensory-motor polyneuropathy associated with a monoclonal IgM gammopathy. In each case, the M-component was shown to display an antibody activity against the Myelin-Associated Glycoprotein (MAG) in a western blot technique. Sera from the three patients stained specifically the myelin sheaths of normal human peripheral nerves after incubation with rabbit anti-IgM. Motor conduction velocities were very low in each case. Morphological studies of the sural nerve from one patient revealed a moderate loss of myelinated fibres, some onion-bulbs but also a microangiopathy and signs of axonal degeneration.