BACKGROUND :
Essential thrombocythemia (ET) in children is a rare chronic myeloproliferative disorder characterized by a sustained proliferation of megakaryocytes, which leads to increased numbers of circulating platelets. Major complications are thrombosis, bleeding, and microvascular occlusive symptoms, sometimes resulting in serious morbidity. Although the indication for treatment of symptomatic patients seems to be clear and several therapeutic modalities can be used, treatment of asymptomatic young patients remains controversial and is individualized according to the centers.
METHODS :
Four children were diagnosed as ET according to the criteria of the Polycythemia Vera Study Group at the department of pediatrics, Kyungpook National University Hospital in Daegu, Korea from January 1998 to February 2003. Hydroxyurea (HU) was started with a dose of 20mg/kg.
RESULTS : HU in starting doses of 20mg/kg/day reduced the platelet count to less than 600,000/mm(3) in 14 to 28 days in three cases and 3 months in one case. Adverse effects of the drug, such as leukopenia and anemia, were observed in 3 cases.
CONCLUSION :
HU was effective in managing the children with ET, but was associated with adverse events such as leukopenia and anemia. We therefore recommend anagrelide be considered as first-line drug in the treatment of ET.

Keywords: Hydroxyurea, Essential thrombocythemia, Children