Polycythemia vera (PV) is an acquired hematologic stem cell disorder of clonal origin. It is rare in the pediatric population, and very few cases have been described. Common presenting complaints include itching, headache, weakness, and dizziness. Patients appear plethoric and often have elevated blood pressures. Enlargement of the spleen and liver is common. Patients are at risk for thrombosis and hemorrhage. In addition to increased hemoglobin and hematocrit values, peripheral blood findings include moderate thrombocytosis and leukocytosis. These findings, along with an increase in the red blood cell mass, are part of diagnostic criteria developed by the Polycythemia Vera Study Group. Bone marrow specimens are usually hypercellular with increased megakaryocytes. Although there have been a variety of nonrandom cytogenetic abnormalities detected in a few patients at diagnosis, none of them is specific for PV, and their incidence increases with time from diagnosis. Erythropoietin levels are typically low and do not increase in response to phlebotomy. Demonstration of the growth of erythroid progenitors in vitro in the absence of erythropoietin (or endogenous erythroid progenitors [EECs]) is considered a hallmark of the disease.

Therapy is directed toward the reduction of the erythrocyte mass through phlebotomy. Hydroxyurea or interferons are currently preferred above radioactive phosphorus or the use of alkylating agents. Phlebotomy to reduce the hematocrit to 45% should be the initial approach for pediatric patients, unless complicating factors contribute to hyperviscosity and vasoocclusive events. The literature on PV patients has suggested that iron deficiency in adults induced by repeated phlebotomies may increase the long-term risk for thrombosis.
For this reason, along with the possible consequences of iron deficiency on child development, iron supplementation may be considered in polycythemic pediatric patients requiring regular phlebotomies. Acute myeloid leukemia may develop during the patient’s course, and its incidence may be increased by therapy with alkylating agents. Myeloid fibrosis is another possible complication of PV and bone marrow transplantation should be considered for these patients.