Thrombocytosis: a retrospective study of 165 dogs

Abstract

Thrombocytosis has been associated with various conditions, including inflammation, neoplasia, iron deficiency, splenectomy, and drug administration. The aim of this study was to characterize diseases and conditions associated with thrombocytosis in dogs. In this retrospective study, dogs with thrombocytosis (platelet count > 600 × 10(3) /μL) and complete medical records during a 1-year period were included, and breed, sex, age, CBC results, alkaline phosphatase and gamma-glutamyltransferase activities in some dogs, administration of glucocorticoids or vincristine, and primary diagnosis were evaluated. Thrombocytosis was found in 240 of 5342 dogs (4.6%), and 165 (3.1%) met inclusion criteria. Thrombocytosis was secondary in all dogs, and underlying diseases and conditions (n,%) were neoplasia (56, 33.9%), inflammation (55, 33.3%), miscellaneous disorders (26, 15.8%), neoplasia plus a second disease (13, 7.9%), endocrine diseases (8, 4.8%), and multiple diseases (7, 4.2%). In dogs with neoplasia, carcinomas (24) and round cell neoplasms (20), especially lymphoma and mast cell tumor, were the most frequent tumors. Inflammatory disorders consisted of immune-mediated disorders (11), neurologic diseases (8), infectious diseases (6), allergic disease (5), orthopedic diseases (4), gastrointestinal diseases (4), and miscellaneous conditions (17). Of the 165 dogs, 73 (44.2%) had received glucocorticoids (55) or vincristine (18) Marked (850-969 × 10(3) platelets/μL) or extreme ( ≥ 970 × 10(3) platelets/μL) thrombocytosis occurred in 24 (14.5%) dogs; 12 (50.0%) had neoplasia. Thromboembolism occurred in 13 (7.9%) dogs. Thrombocytosis in dogs occurred most frequently secondary to neoplastic and inflammatory diseases and was commonly associated with glucocorticoid and vincristine administration. Thromboembolic complications occurred in a small number of patients. Marked or extreme thrombocytosis was more likely to occur with neoplasia than with other conditions.