Peripheral nerve damage during multiple myeloma and Waldenstrom's macroglobulinemia: an ultrastructural and immunopathologic study.

Peripheral nerve biopsies of 22 patients who were seen with a peripheral neuropathy were studied. On each occasion an ultrastructural study was performed and on 12 occasions an immunopathologic study was done. Ten patients had Waldenström's macroglobulinemia and 12 had multiple myeloma. Cellular infiltrates were observed in three cases of Waldenström's macroglobulinemia by light microscopy. A widening of the myelin sheath, corresponding to an accumulation of macroglobulin, was found in three cases of Waldenström's macroglobulinemia. The presence of abundant deposits of amyloid was noted in one case of multiple myeloma. These diverse features show the various possible mechanisms that can produce peripheral nerve damage during the course of malignant dysglobulinemias. The segmental demyelination is probably of immunologic origin. The axonal lesions cannot be explained satisfactorily except in those rare cases where amyloid deposits are present in the endoneurium.