Sickle cell thalassemia, thrombocytosis, and erythrocytosis.

A patient with sickle cell beta+-thalassemia had thrombocytosis and erythrocytosis due to a myeloproliferative disorder best classified as polycythemia vera. RBC counts were 6 to 8 million/cu mm and the red cell mass was 33 ml/kg. A higher red cell mass and an increased hematocrit value were prevented probably by factors related to the hemoglobinopathy, such as microcytosis and hemolysis. The diagnosis of polycythemia vera in patients with sickle cell disease may be difficult to document and the association of these disorders has not been previously reported. This patient's high red blood cell and platelet counts did not result in recurrent vasoocclusive crises.