Monoclonal and biclonal immunoglobulin-producing disorders.

Monoclonal gammopathies are B lymphocyte-derived disorders producing a specific monoclonal immunoglobulin. The group includes multiple myeloma, Waldenström's macroglobulinaemia, monoclonal gammopathy of undetermined significance (MGUS) and heavy-chain disease. In 1% of the cases a double M-component is present which is referred to as a biclonal gammopathy. The pathogeneses of these disorders are unknown, but several possibly related environmental factors have been identified. In multiple myeloma, an increased incidence and mortality rate has been noted during the last 20 years. Strong lines of evidence are presented showing that, in monoclonal gammopathies, the cell clone consists of B lymphocytes in different stages of maturation. In most cases of biclonal gammopathy there is probably a common cellular origin.