Pure red cell aplasia in cats: 9 cases (1989-1997).

OBJECTIVE: To evaluate clinical features, laboratory test results, treatment, and outcome of FeLV-negative cats with pure red cell aplasia (PRCA) diagnosed by examination of bone marrow.

DESIGN: Retrospective study.

ANIMALS: 9 cats.

PROCEDURE: Medical records and smears of bone marrow aspirates were reviewed to determine clinical features, laboratory test results, treatment, and outcome of this syndrome in cats.

RESULTS: PRCA was diagnosed in 9 cats that were between 8 months and 3 years old. Cats had 2- to 16-day histories of lethargy and anorexia, and a severe normocytic, normochromic to hypochromic, nonregenerative anemia (Hct range, 6 to 15%; reference range, 25 to 45%). Other hematologic values were generally within reference ranges. Consistent changes in biochemical profiles included high aminotransferase activities and hyperferremia. Cats were seronegative for FeLV and feline immunodeficiency virus. Smears of bone marrow aspirates were characterized by absence of identifiable erythroid precursors and a high proportion of small lymphocytes. Abnormalities were not identified in megakaryocytes or myeloid cells. Treatment with immunosuppressive drugs (corticosteroids and cyclophosphamide or cyclosporin) resulted in resolution of anemia within 3 to 5 weeks. Most cats required long-term treatment to maintain Hct within reference range and tended to relapse when treatment frequency or dosage was decreased (especially if done rapidly) or treatment was discontinued.

CLINICAL IMPLICATIONS: PRCA is a rare syndrome in young FeLV-negative cats, and is characterized by severe nonregenerative anemia and absence of erythroid cells in bone marrow. The condition requires prompt, aggressive, often long-term treatment with immunosuppressive drugs for resolution.