Childhood essential thrombocytosis.

摘要

We report a 5-year-old female who was incidentally found to have thrombocytosis (platelet count 1,783 x 10~9/L) on routine laboratory investigations before tonsillectomy. Reactive thrombocytosis was excluded by multiple serological and immunological tests. On clinical and ultrasonography investigation she had splenomegaly. There was no family history of thrombocytosis. Cytogenetics showed normal 46XX karyotype with absence of the Philadelphia chromosome. Bone marrow aspirate was markedly hypercellular with numerous clusters of megakaryocytesand platelet clumps. In agreement with the Polycythemia Vera Study Group (PVSG) criteria (platelet count >600 x 10~9/L, absence of conditions associated with reactive thrombocytosis, normal iron stores, normal red cell mass, and absence of Philadelphia chromosome) our patient was diagnosed with essential thrombocytosis (ET). Hydroxyurea, 15 mg/kg daily, was administered for 15 days until normalization of platelet count. One year later, she remains in good health andtonsillectomy was successfully performed without any haemorrhagic complications.ET is a myeloproliferative disorder of unknown origin that has usually been considered a disease of the middle-aged. It is extremely rare in childhood with an annual incidence about 1 per 10 million, 60 times lower than in adults. Forty eight other children have been reported in the literature. Their age ranged from 6 weeks to 18 years with median age at diagnosis of 11 years. Splenomegaly is a common clinical feature, in agreement with thrombocytosis of clonal disorder.