Clinical findings, diagnostics and treatment results in primary and secondary immune-mediated thrombocytopenia in the dog

Thrombocytopenia (< 150,000/<mu>l) was observed in 268 dogs at the Small An imal Hospital at the University of Berlin during a 2 year period. Platelet- bound antibodies were determined in 58 of these dogs. These dogs are furthe r described in this study. The platelet-bound antibody test was positive in 41 dogs with thrombocytope nia. A primary immune-mediated thrombocytopenia (pITP) was diagnosed in 15 dogs based on the positive antibody test result, exclusion of other disease s, and response to immunosuppressive therapy. Nine dogs with pITP also had an anemia and a positive Coombs' test result: thus these dogs also had a pr imary immune hemolytic anemia (Evans' syndrome). Clinical signs of hemorrhage were observed in 12 of 15 dogs with pITP and i n 6 of 9 dogs with Evans' syndrome, characterized by surface bleeding in 17 of 18 dogs. Platelet counts ranged from 0-74 000/mul (diameter 10 400/mul) in dogs with pITP and from 10 000-143 000 (diameter 46 900/mul) in dogs wi th Evans' syndrome, 21 of them had platelet counts < 30 000/<mu>l. Five dog s with pITP and 8 dogs with Evans' syndrome were moderately to severely ane mic. A mild splenomegaly and/or hepatomegaly was documented radio- and ultr asonographically in 10 dogs with pITP and 7 with Evans' syndrome. After 2-1 1 days (diameter 4.4 days) of immunosuppressive treatment with prednisolone , azathioprine or vincristin, platelet counts rose in 13 of 14 severely thr ombopenic clogs (< 50 000/<mu>l) to 48 000-112 000/mul. Dogs with Evans' sy ndrome were treated with prednisolone, azathioprine or cyclosporine. The 7 severely thrombopenic dogs (<50,000/<mu>l) had a rise in platelet counts > 50 000/mul in 2-6 days (diameter 3.3 days). Recurrence rate in dogs with pI TP while receiving drugs or after withdrawel was 40 % in the 10 dogs with a dequate follow-ups. In 4 of 8 dogs with Evans' syndrome the platelet count declined while being treat or following withdrawel. One dog with pITP and o ne with Evans' syndrome were euthanized. An underlying disease was diagnosed (platelet counts 1 000-119 000/mul, dia meter 31 000/mul) in 17 dogs with a positive platelet-bound antibody test r esult suggesting a secondary ITP (sITP). Twelve of the 17 dogs had an infec tious disease (babesiosis, ehrlichiosis, leishmaniasis, abscess, prostatiti s), 4 had neoplasia (lymphoma, liver or splenic tumor) and 1 dog developed thrombocytopenia after a blood transfusion. In 9 of 12 dogs with infections platelet counts increased after treatment of the underlying disease, 3 dog s also received prednisone. In conclusion the platelet-bound antibody test was useful in diagnosing ITP in dogs. A positive platelet-bound antibody test result was, however, not specific for pITP and other causes of ITP have to be carefully excluded.