A case of refractory anemia with ring sideroblasts and associated thrombocytosis.

A 69-year-old man presented with a 2-year history of progressive thrombocytosis, referred to exclude essential thrombocythemia. He had been asymptomatic apart from intermittent dysphagia and a brief episode of amaurosis fugax a few weeks prior to his presentation. On examination, he had no palpable splenomegaly. Complete blood count showed the following: hemoglobin, 129 g/L; mean corpuscular volume, 85 fL; platelets, 930 3 10/L; and white blood cell count, 9.3 3 10/L. The peripheral blood smear showed marked thrombocytosis, giant platelets, and red cell dysplastic changes including oval cells, target cells, numerous red cell stippling, and Pappenheimer bodies (panel A). These findings suggested acquired sideroblastic anemia and an associated myeloproliferative neoplasm. Molecular studies showed the Janus kinase 2 V617 mutation was positive.