Anemia, splenomegaly, and increased osmotic fragility of erythrocytes in Abyssinian and Somali cats

Objective-To determine clinical and clinicopathologic features of a chronic intermittent severe hemolytic anemia characterized by erythrocyte osmotic fragility in Abyssinian and Somali cats. Design-Case series. Animals-13 Abyssinian and 5 Somali cats. Procedures-History, pedigree information, and results of routine laboratory tests, special erythrocyte studies, and histologic evaluation of splenic a nd hepatic specimens were analyzed. Results-Age at which clinical signs of anemia were first apparent ranged fr om 6 months to 5 years. Ten cars had splenomegaly. Most often, the PCV was between 15 and 25%, but it was as low as 5% at some times. The anemia was c haracterized by macrocytosis and mild To moderate reticulocytosis, but no p oikilocytosis. Hyperglobulinemia, lymphocytosis, mild hyperbilirubinemia, a nd high hepatic enzyme activities were common findings. Results of Coombs t ests and tests for infectious diseases were negative. The erythrocytic osmo tic fragility was high in affected cats (mean osmotic fragility, 0.66 to 0. 78%), compared with healthy cats (0.48 to 0.58). No specific membrane prote in abnormality, erythrocyte enzyme deficiency, or hemoglobinopathy was iden tified. Histologic evaluation of splenic and hepatic specimens revealed ext ramedullary hematopoiesis and hemosiderosis. Four of the 5 Somali cats were closely related. Conclusions and Clinical Relevance-On the basis of results of pedigree anal yses, the apparent breed predilection, and the exclusion of other known cau ses of anemia in cats, we believe that the hemolytic anemia in these cats w as likely a result of a novel hereditary erythrocyte defect. A genetic pred isposition to immune-mediated destruction of erythrocytes could not be rule d out.