Abstract
Simple SummaryAmong chronic Ph-negative myeloproliferative neoplasms, essential thrombocythemia is found in children with low but increasing incidence. The diagnostic and clinical features do not completely overlap with ET of adult age. A significant number of cases, in fact, do not meet the criteria of clonality, and many cases require extensive clinical evaluation to exclude secondary, reactive forms. Therefore, histological analysis of bone marrow biopsy is necessary, and its use should be enforced. The clinical course appears to be more benign, at least within the first decades of observation, with the incidence of thrombotic events being much lower than in adults (4 % vs. 30%). Hemorrhages are mostly irrelevant. Therefore, the management should be carefully adapted to the individual patient, balancing the risk of future complications with long-term collateral effects of any drug. This review analyzes the peculiarities of the disease facing similarities and differences with adult scenarios.This paper reviews the features of pediatric essential thrombocythemia (ET). ET is a rare disease in children, challenging pediatric and adult hematologists alike. The current WHO classification acknowledges classical Philadelphia-negative MPNs and defines diagnostic criteria, mainly encompassing adult cases. The presence of one of three driver mutations (JAK2V617F, CALR, and MPL mutations) represent the proof of clonality typical of ET. Pediatric ET cases are thus usually confronted by adult approaches. These can fit only some patients, because only 25–40% of cases present one of the driver mutations. The diagnosis of hereditary, familial thrombocytosis and the exclusion of reactive/secondary thrombocytosis must be part of the diagnostic process in children and can clarify most of the negative cases. Still, many children present a clinical, histological picture of ET, with a molecular triple wild-type status. Moreover, prognosis seems more benign, at least within the first few decades of follow-up. Thrombotic events are rare, and only minor hemorrhages are ordinarily observed. As per the management, the need to control symptoms must be balanced with the collateral effects of lifelong drug therapy. We conclude that these differences concert a compelling case for a very careful therapeutic approach and advocate for the importance of further cooperative studies.
Highlights
Essential thrombocythemia (ET), one of the Ph-negative Chronic Myeloproliferative neoplasms (MPNs), develops as an acquired clonal defect of myeloid precursor cells driving uncontrolled myeloid proliferation [1]
Within MPN, ET is characterized by high platelet counts, a finding which can be found in polycythemia vera (PV), myelofibrosis (MF) and chronic myeloid leukemia (CML) [2]
Diagnosis of ET as well as of other MPNs has long been addressed by adult hematology and was recently confirmed within the WHO classification of myeloid neoplasm [3,4], gaining from the insight given by the identification of driver mutations and peculiar histological patterns (Table 1)
Summary
Essential thrombocythemia (ET), one of the Ph-negative Chronic Myeloproliferative neoplasms (MPNs), develops as an acquired clonal defect of myeloid precursor cells driving uncontrolled myeloid proliferation [1]. Some papers [14,15,16,17,18] suggest that ET in children is different than in adults, with lower incidences of thrombotic and hemorrhagic complications and scarce or no evolution into myelofibrosis and acute leukemia This poses questions regarding the opportunity of adapting the available hematological and management criteria to pediatric patients. In ET ( commonly assumed as primary thrombocytosis), the increase in platelet count depends on a clonal disease of the bone marrow. These forms were grouped as myeloproliferative diseases and were later considered myeloproliferative neoplasms by the 2016 WHO classification [3,4] and comprise different entities, such as BCR-ABL-positive chronic myeloid leukemia, chronic eosinophilic leukemia, mastocytosis, some myelodysplastic syndromes, and the three entities within BCR-ABL-negative chronic MPN, i.e., ET, PV and MF. ET is recognized more frequently than in the past and an incidence of 0.6/100,000/year has been reported in children and young people under the age of 20 [43], probably due to the increased number of automated blood counts performed in children [18], and case series, case reports, have been published in recent years [8,15,16,17,18,43,44]
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