Serum and urinary immunofixation electrophoresis in a dog with multiple myeloma

Multiple myeloma (MM), a neoplasm of plasma cells or their precursors, is a lymphoproliferative disorder usually associated with a monoclonal gammopathy. Immunofixation electrophoresis (IFE) is considered the gold standard to detect and identify the suspected monoclonal component (MC). A 10-year-old crossbreed dog was presented because of lethargy, weight loss, polyuria/ polydipsia and exophthalmos. Blood tests revealed anemia, thrombocytopenia and hyperproteinemia with a narrow spike in the b2-g region of the electrophoretic pattern. Urinalysis showed a urinary proteine/creatinine ratio of 4.51 and a mixed incomplete proteinuria using sodium-dodecil-sulfate agarose gel electrophoresis. The bone marrow cytology showed the presence of 25% atypical plasma cells. The MC was identified as IgA-l type both in serum and urine by IFE using mammalian immunoglobulins anti-human heavy (gamma, alpha and mu) and light (kappa and lambda, both free and bound) chains. Paraproteins were quantified in the serum by densitometric scanning of high resolution agarose gel (72.4 g/L). Bence-Jones proteins were not found in the urine by IFE. Treatment with melphalan (2 mg/day PO), prednisone (12.5 mg/day PO) and benazepril (10 mg/day PO) was started. After 2 months of therapy complete clinical remission was obtained and serum paraprotein concentration decreased to 3 g/L. Atypical plasma cells were still detectable on bone marrow cytology, but were markedly reduced (15%). We highlight the cross-reaction between anti-human heavy and light chains (kappa and lambda, free and bound) and canine heavy and light chains. The use of IFE has proved crucial to the diagnosis ofMMand to monitoring the course and treatment of disease