Waldenström's macroglobulinemia in a dog with a bleeding diathesis.

An 11-year-old female spayed Whippet dog was referred to the Veterinary Hospital of the National Veterinary School of Lyon with a 3-month history of chronic bleeding, cutaneous masses suggestive of hematomas, and hemorrhagic diarrhea. Laboratory abnormalities included leukopenia with neutropenia and lymphopenia, rouleaux formation, marked hyperproteinemia with hyperglobulinemia and normoalbuminemia, hypercalcemia, markedly increased serum urea concentration, mildly increased creatinine concentration, and proteinuria. Hemostatic screening tests showed marked prolongation of thrombin time, increased concentrations of fibrin(ogen) degradation products and D-dimers, and slightly prolonged activated partial thromboplastin time. Serum and urine protein electrophoresis revealed a monoclonal peak identified as IgM by immunoelectrophoresis and an M-spike, respectively. Cytologic evaluation of bone marrow revealed a hypocellular sample with lymphoplasmacytic cells comprising approximately 50% of all nucleated cells. These findings were consistent with a diagnosis of Waldenström's macroglobulinemia with secondary bleeding diathesis. Treatment with prednisone and chlorambucil was initiated, and the dog had a good response. ©2011 American Society for Veterinary Clinical Pathology.