[Studies on 13 cases of double gammopathy].

By a combined use of immunoelectrophoresis and immunofixation, we detected 13 cases of double gammopathy among 269 cases of monoclonal gammopathy investigated between 1986 and 1990. The incidence of double gammopathy (4.8%) was greater than that in previous studies. Double gammopathy was classified into 5 groups: (1) identical pairs of both heavy (H)- and light (L)-chains (1 case); (2) identical H-chains and different L-chains (2 cases); (3) different H-chains and identical L-chains (3 cases); (4) different pairs of both H- and L-chains (5 cases); and (5) monoclonal immunoglobulin and Bence Jones protein of different type (2 cases). An additional M-component was detected during the course of illness in 2 of the 13 cases. As to H-chain combinations, a pair of IgG and IgA (46%) was most frequently encountered. Seven patients had myeloma, three benign double gammopathy and two macroglobulinemia. One case of benign double gammopathy developed IgA (lambda) myeloma three years after the diagnosis. Serum and urine immunofixation is a useful method to detect a trace amount of M-component and to follow up the clinical course of monoclonal gammopathy.