RESUMEN
Erythrocytosis is a rare disorder in childhood and is mainly secondary to causes such as long-term chronic cardiopulmonary diseases or haemoglobin dysfunction. In some cases, polycythaemia is found when renal, hepatic or cerebellar tumours are diagnosed. Polycythemia vera (PV) is uncommon in paediatrics and usually clinical and biological features are used to diagnose and classify PV. The V617F mutation of JAK-2 has been described recently and is found in almost 90% of adult patients with PV. This mutation allows now a reliable and early diagnosis. Therapeutic management is based on phlebotomy and cytoreductive therapy. In young adults and children, interferon alpha is theoretically superior as it is effective and there is no risk of inducing leukemia. We report here a case of PV in a 10-year-old girl with the V617F JAK-2 mutation.