Steroid-responsive neutropenia in a cat with progressive feline leukemia virus infection

An 8-month-old female domestic shorthair cat was presented to the Animal Medical Center with anorexia, lethargy, and mild gastrointestinal signs. A CBC revealed a profound neutropenia, and serologic testing with an in-house test kit (SNAP FIV/FeLV Combo, IDEXX) was positive for feline leukemia virus (FeLV) antigen. Serial hematologic examinations during hospitalization showed a persistent neutropenia with occasionally severe anemia and thrombocytopenia. Prednisolone administration afforded complete hematologic remission within 3 days. Four weeks after the premature discontinuation of prednisolone, the patient relapsed; however, complete and prolonged hematologic remission was achieved after prednisolone was re-induced. Bone marrow aspiration cytology was consistent with immune-mediated destruction of the mature myeloid cells. Steroid-responsive (likely immune-mediated) cytopenias rarely occur in cats with progressive FeLV infection. Although only a few cases of FeLV-positive, severely neutropenic cats that responded to immunosuppressive therapy have been reported, this case highlights that a grave prognosis should not always be given to these FeLV-positive cats.