Essential Thrombocythemia in a Two-year-old Child, Responsive to Hydroxyurea but Not Aspirin.

Essential thrombocythemia (ET) is a myeloproliferative neoplasm that occurs mostly in patients above the age of 50 years. Its incidence in children is very rare, with around 100 cases reported in the literature. High-risk patients are defined by previous life threatening major thrombotic or severe hemorrhagic complication or age > 60. Those patients probably benefit from cytoreductive therapy. On the other hand, antiplatelet drugs are recommended for patients with low risk group. Although rare, ET should be considered in the differential diagnosis of persistent thrombocytosis in children, even at a very young age. A constellation of clinical, pathologic, and molecular testing are essential for diagnosis. Given the rarity of these cases, there is currently no consensus for treatment guidelines in children, especially in asymptomatic patients. We describe a case of a two-year old girl who presented with unexplained, isolated thrombocytosis which persisted for eight years. Bone marrow biopsy demonstrated typical features of ET. Over the course of the disease, hydroxyurea, but not aspirin, showed better control of symptoms and lowered the platelets level.