Thrombocytopenia associated with neoplasia in dogs.

Ten percent (214/2,059) of all dogs with cancer at North Carolina State University Veterinary Teaching Hospital had thrombocytopenia. The thrombocytopenia was associated with infectious/inflammatory etiologies in 4%, miscellaneous disorders (therapy, bone marrow failure, disseminated intravascular coagulation) in 35%, and neoplasia without identifiable secondary factors in 61% of cancer-bearing dogs. Classifying these dogs by tumor groups revealed the following proportionate ratios: lymphoid, 29%; carcinoma, 28%; sarcoma, 20%; hemic neoplasia, 7%; multiple, 5%; unclassified, 3%; benign, 3%; brain, 3%; and endocrine, 3%. Dogs with hemangiosarcoma, lymphoma, and melanoma were at increased risk of developing thrombocytopenia. Cytotoxic therapy was the major factor increasing the risk of thrombocytopenia in dogs with melanoma. Golden Retrievers were the only breed recognized with a predisposition to develop thrombocytopenia. If thrombocytopenia is identified in a dog with cancer, we recommend thorough evaluation of the coagulation system before surgery or therapy, and careful consideration of the risks and potential benefits of myelosuppressive or L-asparaginase therapy.

An epizootic of peroneal and tibial neuropathy in Walker Hound pups.

Early in life, Walker Hound pups from several litters, later determined to have peroneal and tibial neuropathy, had been given supplements of either evaporated milk and corn syrup mixed with well water or powdered bitch milk formula mixed with well water. Other pups not given supplements were not affected. Pelvic limb monoparesis, areflexia, analgesia, and muscular atrophy developed by 2 weeks of age. Abnormalities detected by light and electron microscopy included scattered swollen axons containing increased organelles and whorled neurofilaments. The clear association between clinical signs of disease and dietary supplementation of pups among healthy dogs in a kennel, as well as lack of an obvious pattern of inheritance, suggested an environmentally acquired toxin, specifically the well water. Attempts to reproduce neuropathy in a litter of Beagle pups 2 years after initial evaluation of the disease syndrome were unsuccessful. Atomic absorption studies performed on the well water to detect heavy metals did not reveal toxic concentrations. Toxins that may have been responsible for the neuropathy in these pups were not identified.

Therapy of immune mediated thrombocytopenia. A retrospective study of 15 dogs.

Fifteen dogs with immune mediated thrombocytopenia (IMT) were studied retrospectively. All dogs had a thrombocyte count below 50,000/microliters when response to therapy was studied. Platelet counts greater than 50,000/microliters were present in all dogs within 2-9 days of initiating medical therapy. Eight dogs experienced a single episode of thrombocytopenia and seven dogs relapsed over the following 5 to 24 months. Clinical parameters from dogs that experienced a single episode of IMT were compared with data from dogs that relapsed to determine whether any information would identify dogs that were prone to relapse. Signalment, severity of thrombocytopenia, and time to achieve a platelet count above 50,000/microliters were found not to differ (P greater than 0.05) between these two groups. Five of the seven dogs with relapsing IMT were splenectomized after 2 to 4 episodes (mean, 2.8 +/- 0.8) of thrombocytopenia over 2 to 14 months. The postoperative progress of these five dogs was followed for 6 to 17 months. Platelet counts were sustained above 200,000/microliters in 4/5 after splenectomy and it was possible to discontinue medical therapy in these dogs. In comparison, the 2 relapsing IMT cases that were not splenectomized continued to require intermittent immunosuppressive therapy. We conclude that signalment and routine pretreatment laboratory test results are not useful in distinguishing dogs with relapsing IMT from those that will experience one episode of IMT. Seemingly, splenectomy is useful in the management of dogs with relapsing IMT.