Multiple myeloma in a six year old Labrador Retriever

Abstract

Multiple myeloma is responsible for approximately eight percent of all canine hematopoietic tumors and is accountable for 3.6 percent of all neoplasias affecting the bones of dogs. It is a neoplasia of the plasma cells in the bone marrow. Classically, diagnosis of canine multiple myeloma is made based on the presence at least two of the following four criteria: 1) bone marrow plasmacytosis of greater than five percent, 2) radiographic evidence of osteolysis, 3) monoclonal gammopathy on serum or urine electrophoresis, and 4) Bence-jones proteinuria. Many of the clinical signs and complications associated with multiple myeloma are caused by the overproduction of the M component (immunoglobulins) by neoplastic plasma cells. In dogs, the immunoglobulins produced excessively are IgG, IgA, and IgM (macroglobulinemia). If there is only abnormal over-production of the immunoglobulin light chains, Bence-jones proteinuria is observed. In rare cases, such as a nonsecreting multiple myeloma, some of the criteria for diagnosis may be absent. Diagnosis is then made by the extent of bone marrow plasmacytosis and the presence of neoplastic plasma cells.