Renal pathology of Waldenström's macroglobulinaemia with monoclonal antiglomerular antibodies and nephrotic syndrome.

Severe nephrotic syndrome developed suddenly in a 67-year-old man. IgM M-component and bone marrow findings indicated a diagnosis of Waldenström's macroglobulinaemia. High-titre IgM glomerular autoantibodies were found to reside mainly in the M-component. Immunofluorescent (IF) studies on serial kidney biopsies showed extensive IgM deposits that disappeared after treatment. Light microscopy of kidney biopsy appeared only slightly altered, but combined with electron microscopy could demonstrate changes that correlated well with IF findings. The latest biopsy showed interstitial infiltration in the kidney of atypical lympho-histiocytic cells. Morphological and immunological examination indicated that pathogenetic events started with minimal-change glomerulonephritis, causing release of glomerular antigen, that finally triggered a monoclonal IgM response and lymphoproliferative reaction. Intermittent treatment with chlorambucil and corticoids completely abolished the nephrotic syndrome and at the same time the changes in renal morphology largely disappeared.