Abstract
BACKGROUND: Polycythemia vera is a myeloproliferative disease that sometimes evolves to myelofibrosis, causing splenomegaly and neutropenia. In this case report, we describe a patient with polycythemia vera and unexplained neutropenia who later turned out to also have hairy cell leukemia. CASE PRESENTATION: A middle-aged Caucasian man with polycythemia vera presented to our hospital with chronic mouth ulcers. Later he developed leukopenia and pancytopenia. Bone marrow biopsies showed fibrosis. Further morphological analyses of bone marrow and blood smears revealed probable transformation into acute myeloid leukemia. However, there were also cells indicating hairy cell leukemia. Morphological and immunohistochemical analyses later confirmed the presence of hairy cell leukemia in biopsies that had been present for 3 years. Treatment with cladribine temporarily reversed the patient's neutropenia. CONCLUSIONS: Hairy cell leukemia may mimic development to myelofibrosis in patients with polycythemia vera.