Immune complex glomerulonephritis with unusual microfibrillar deposits associated with primary bone marrow lymphoma

Glomerular microfibrillary deposits are characteristic of several diseases of the kidney. In a number of glomerulopathies, the nature of these microfibrillary deposits is critical in classifying the renal lesion and in suggesting the possibility of an associated systemic process. However, it is likely that as efforts are made to classify glomerulopathies with microfibrillary deposits, certain cases will defy categorization. We describe one such case in which a patient presented with rapidly progressive glomerulonephritis associated with large subepithelial, parallel-arrayed microfibrillar deposits associated with a primary bone marrow B-cell lymphoma. While IgG, C3, and lambda and kappa light chains were deposited in the glomerulus, serum and urine protein electrophoresis were normal. Treatment with Cytoxan and prednisone caused simultaneous remission of the lymphoma and the glomerulonephritis. Relapse of the lymphoma was associated with rapid deterioration of renal function. This case may represent a newly described variant of immune complex-mediated glomerulonephritis associated with microfibrillary deposits. The possibility is raised that the glomerular lesion is due to atypical immunoglobulins synthesized by a bone marrow lymphoma.