A retrospective study of 19 cases of canine myelofibrosis.

Nineteen cases of myelofibrosis were identified among 456 canine bone marrow specimens submitted for analysis. Myelofibrosis was classified as primary in I dog and as secondary in 18 dogs. Clinical conditions associated with secondary myelofibrosis included immune-mediated hemolytic anemia (n = 5), neoplasia (n = 4), and long-term drug treatment (n = 4). Drugs administered included phenobarbital, phenytoin, phenylbutazone, and colchicine. Bone marrow necrosis was observed in 5 dogs. Eight dogs were treated with immunosuppressive doses of prednisolone, and 3 were treated with erythropoietin. Half of the dogs with secondary myelofibrosis recovered from their cytopenias and were alive from 4 months to 5 years after diagnosis.