Immunoglobulin A myeloma in a cat with pleural effusion and serum hyperviscosity

Immunoglobulin A myeloma, serum hyperviscosity, and septic pleuritis were diagnosed in a cat with pleural and peritoneal effusions. Serum hyperviscosity was determined by use of a WBC pipette, and clinical manifestations included retinopathy and cardiac changes. The presence of Salmonella typhimurium in the pleural fluid may have resulted from increased susceptibility to infection. Postmortem examination revealed plasma cell infiltration of the pleura, mesenteric lymph nodes, and the serosa of the intestine, liver, and spleen. This case represents an unusual form of myeloma in the cat.