Chronic lymphatic leukemia developing in a patient with multiple myeloma: immunologic demonstration of a clonally distinct second malignancy.

A patient with multiple myeloma who subsequently developed chronic lymphocytic leukemia is reported. Initial studies demonstrated clinical and hematological features of multiple myeloma with an IgM lambda paraprotein. Skeletal disease was a significant presenting feature, although relapse occurred in extraosseous sites, particularly the pleura. He developed chronic lymphatic leukemia 31 months later and immunological studies showed the malignant lymphocytes to have kappa (Kappa) light chain surface immunoglobulin, demonstrating separate clonal origin of this patient's two B-cell malignancies.