Essential thrombocythemia in children.

PURPOSE: The objective of this study was to evaluate the clinical course, laboratory findings, and outcomes of children with essential thrombocythemia (ET).

PATIENTS AND METHODS: The authors analyzed 36 children, ages 6 weeks to 18 years, by combining descriptions of 2 patients observed at their institution with 34 patients reported in the English medical literature.

RESULTS: Fifteen patients (10 at diagnosis and 5 later on) had symptoms directly related to ET, including 9 who had severe thrombohemorrhagic phenomena. Common abnormalities included large platelets, increased marrow megakaryocytes with hyperlobulated forms, and abnormal platelet aggregation. Symptomatic patients had significantly higher platelet counts (2,419 versus 904 x 10(9)/L, P < 0.001); however, three patients with platelet counts that were only moderately elevated (600-800 x 10(9)/L) had thrombotic events. Eleven patients received various therapeutic agents. Interestingly, three patients who had one thrombotic event, and did not receive therapy, went on to have a benign clinical course. Leukemia developed in two treated patients, and they died; two others died of thrombotic complications; and myelofibrosis developed in one patient. Seventeen cases (47%) were familial. Patients with familial cases had significantly lower platelet counts, a lower incidence of hepatomegaly, and no thrombotic complications.

CONCLUSIONS: This analysis of children with ET found that severe vascular complications developed in a substantial number. Platelet counts usually, but not always, correlate with the occurrence of complications. The indications for treatment and the best treatment of children with ET are currently not known, and guidelines for the management of children with ET are needed. Familial thrombocythemia is common among children with primary thrombocytosis and appears to be a different disease from ET, with a more benign course.