Purpose: To report the unusual occurrence of essential thrombocythemia (ET) in a 5-month-old infant.
Patients and methods: The child was referred by her pediatrician for a high platelet count detected on routine blood testing. The child was asymptomatic except for failure to thrive. Diagnostic tests to rule out secondary causes of thrombocytosis as well as myeloproliferative syndrome were done.
Results: The platelet count persisted at > 1,000,000/microliters, and no secondary cause could be established. The bone marrow aspirate and biopsy showed normal cellularity, no fibrosis, orderly maturation, and normal morphology of all three cell lines, with only an increase in the number of megakaryocytes. A diagnosis of ET was established as per the Polycythemia Vera Study Group criteria. In view of the young age of the patient and asymptomatic course of the disease, we decided to observe the child only, reserving antiplatelet agents for use in the event of a thromboembolic or hemorrhagic episode.
Conclusions: This is the youngest known child with ET. We believe that conservative observation is warranted in an asymptomatic child. The child is currently doing well and is asymptomatic 4.5 years after diagnosis.