Lymphoplasmacytic lymphoma. Report of a case with three monoclonal proteins derived from a single neoplastic clone.

The unique case of a 60-year-old patient with a non-Hodgkin's B-cell lymphoma of the lymphoplasmacytic type and three associated monoclonal proteins, is described. The patient also exhibited various autoimmune phenomena that were consistent with the diagnoses of Sjögren's syndrome and autoimmune thyroiditis. The evolution from production of a single monoclonal protein (IgM-kappa) to three monoclonal proteins (IgG-kappa, IgA-kappa, and IgM-kappa) suggested that the lymphoplasmacytic cells were at different stages of terminal differentiation within a single neoplastic clone. The chronic antigenic stress imposed on the immune system by the autoimmune disorder may have played a role in the development of lymphoma and in the heavy chain immunoglobulin switching that occurred during the patients' clinical course.