Macroglobulinemia with abdominal symptoms caused by intestinal extracellular macroglobulin.

A 54-year-old woman had a marked splenomegaly, diarrhoea and abdominal cramps. Her serum contained monoclonal IgM with lambda light chains, and lambda light chains were also excreted in the urine. Bone marrow and spleen punctures failed to reveal the classic morphological changes associated with Waldenström's macroglobulinemia. A peroral jejunal biopsy disclosed homogenous extracellular material consisting of IgM, lambda and kappa light chains were demonstrable in a large number of the plasma cells and plasmacytoid cells in post-mortem specimens of bone marrow, spleen and some lymph nodes by the peroxidase-anti-peroxidase techniques. The causes of the "discrepancy" between the serum findings and tissue findings are discussed.