[Isotype switching of produced immunoglobulins in multiple myeloma].

Multiple myeloma is usually characterized by production of a single serum monoclonal protein of constant isotype and light chain restriction. Isotype switching in human lymphomas appears to be an uncommon event. It could be due to altered para-protein production by the malignant plasma cell clone, or oligoclonal Ig production during recovery of B-cell function after chemotherapy. We describe a case of clonal heavy chain isotype switching in a patient with lymphoplasmocytic lymphoma.