[Gamma heavy chain disease. A new case]

Description of a case presenting as an inflammatory polyarthritis. A uterine sarcoma was detected one year later and led to the death of the patient. The abnormal protein belonged to the gammal subclass. Biosynthesis experiments, performed on the marrow plasma cells, showed that light chains were not produced and that the molecular weight of the monomeric unit of the serum protein was slightly smaller than that of the protein secreted in vitro, suggesting the occurrence of a secondary and limited extracellular proteolysis.