Distribution of heavy chain classes and light chain types in 757 cases of monoclonal gammapathies.

The distribution in heavy chain classes and light chain types of M components were studied in 757 cases of monoclonal gammapathies. These gammapathies were classified according to clinical and hematological data in 439 myeloma (MM), 165 Waldenström's macroglobulinemia (WM) and 152 monoclonal gammapathies occurring in other conditions. The IgG/IgA ratio differs in myeloma and in non-myelomatous gammapathies (64% IgG versus 33% IgA in myeloma and 95% IgG versus 5% in absence of myeloma). Presence of free light chains in patient's urines (Bence Jones proteinuria) was detected in about 72% of cases of MM, 48% of WM and only in 9% in others gammapathies. Concerning the sex of patients, an equal repartition between males and females is observed in MM, whereas males predominate in WM. The age distribution of the patients shows that 74% of myeloma and 79% of WM were above sixty. In addition to the 757 cases under study, 10 sera with two M Components were characterized.