Benign monoclonal gammaglobulinemia and glomerulonephritis.

Serum protein electrophoresis revealed a monoclonal gammopathy in three patients who presented with glomerulonephritis. Other features of myeloma were not found. Clinical manifestations of glomerulonephritis included marked proteinuria and significant hematuria. Rate of progression of renal failure was variable. Morphologically, glomerulonephritis was characterized by diffuse proliferative lesion with predominant mesangial involvement. Immunoglobulins and complement were found deposited in the mesangium. Immunoglobulins deposited in the glomeruli were found to consist exclusively of the circulating monoclonal IgG in one patient. Immunoglobulins eluted from the glomeruli of another patient consisted of immunoglobulin (IgM) which had electrophoretic mobility similar to that of the monoclonal spike in the serum. Selective deposition of monoclonal immunoglobulins in the glomeruli indicated that an active process was involved in their glomerular localization and that the monoclonal immunoglobulins may have had a role in the pathogenesis of glomerulonephritis in these patients.