[Benign monoclonal gammopathies].

The finding in serum and/or urine of IgG, IgA or a monoclonal light chain must prompt a systematic search for a myeloma, a solitary plasmocytoma or an immunoglobulins amyloidosis. Clinical and experimental data suggest that some monoclonal immunoglobulins can remain stable after several years of existence, but at the time of diagnosis there is no criterium to assert with certainty that a monoclonal immunoglobulin will or will not be complicated by a malignant proliferation of plasmocytes. Nothing but a prolonged follow-up enables a diagnosis of "benign" monoclonal gammapathy to be made.