Polycythemia vera (PV) was diagnosed in a four-year-old domestic shorthair evaluated for hind-limb ataxia, extension of all claws, and difficulty in jumping to elevated surfaces. Mild cardiac hypertrophy also was diagnosed. Initial laboratory evaluation revealed polycythemia (packed cell volume [PCV], 75%) and normal serum total protein (7.5 g/dl). Definitive diagnosis of PV was reached by excluding causes of relative and secondary absolute polycythemia using radiography, ultrasonography, and blood gases, and by measuring serum erythropoietin concentration by radioimmunoassay (13 mU/ml) and an enzyme-linked immunosorbent assay (ELISA) method (8.0 mU/ml). Bone-marrow biopsy revealed relative erythroid hyperplasia characteristic of myeloproliferative disease. Clinical signs were controlled with hydroxyurea (12.2 mg/kg body weight) and occasional phlebotomy. Polycythemia vera is an uncommon feline disease, and clinical reports on the use of hydroxyurea to manage the condition in the cat are lacking.
