Chronic lymphocytic leukaemia with subsequent development of multiple myeloma. Evidence of two B-lymphocyte clones and of myeloma-induced suppression of secretion of an M-component and of normal immunoglobulins.

In a patient with chronic lymphocytic leukaemia, two M components of the IgGkappa and IgGlambda classes were demonstrated in the serum at the time of diagnosis. The patient was first followed without treatment; after 18 months multiple myeloma developed. At that time, immunofluorescence study of lymphocytes of the peripheral blood showed mainly membrane-bound immunoglobulins (S-Ig) of the IgGkappa class. The bone marrow disclosed a definite predominance of plasma cells with cytoplasmic IgGlambda, suggesting that the two B cell-derived diseases had arisen from two different cell clones. During the development of multiple myeloma, the serum concentration of the M component IgGlambda increased. Concurrently, the M component of IgGkappa gradually disappeared from the serum, and the concentrations of the normal immunoglobulins IgA and IgM declined. Following cytostatic treatment, the concentration of the myeloma-derived M component IgGlambda was halved and simultaneously the M component IgGkappa reappeared in the serum. To our knowledge, this case is the second reported of chronic lymphocytic leukaemia and multiple myeloma indicating development of the two diseases from different cell clones, and the first reported cases with myeloma-induced suppression of M-component secretion from malignant cells.