Primary cardiovascular amyloidosis with benign monoclonal gammopathy.

A 54-year-old woman is reported whose primary amyloidosis was diagnosed at autopsy. Amyloid deposits were found in the myocardium, the striated muscles, the smooth muscle layers of the gut and the wall of the blood vessels. The deposits showed resistance to induced proteolysis. A large number of mature plasma cells was demonstrated in the bone marrow, and immunocytochemical studies revealed a considerable increase in the proportion of plasma cells which were positive for kappa light chains of immunoglobulins, indicating a monoclonal gammopathy. This view was strongly supported by the unexpected finding that amyloid deposits were positive for kappa light chains. The relationship between the kappa positive reaction of amyloid and its resistance to induced proteolysis are discussed.