Plasmacytic neoplasm of the gastrointestinal tract in a patient with long-standing monoclonal gammopathy.

We have reported the 21-year follow-up of a patient with progressive monoclonal IgG lambda gammopathy and recurrent pneumococcal infections who had diarrhea and weight loss. The serum IgG had risen from 2,850 mg/dl in 1966 to 6,120 mg/dl in 1986, but repeated evaluations had shown no evidence of myeloma or lymphoma. Evaluation revealed infiltration of the gastrointestinal tract by a plasmacytic malignancy with a surface heavy and light chain identical to her serum monoclonal band.