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International audience; No abstract available

Elevated red blood cell distribution width (RDW) has recently gained attention in patients with myeloproliferative neoplasms (MPN) as it was shown to be associated with reduced survival in myelofibrosis [1] and conflicting information has been reported for thrombotic risk in treatment- naïve and exposed polycythemia vera (PV) patients [2, 3, 4]. Due to uncertain implications of this parameter on the thrombotic risk in MPN, we aimed to evaluate RDW and associated thrombotic risk in a multicentric cohort of patients with primary (PMF) and secondary myelofibrosis (SMF).

Secondary thrombocytosis is a frequent secondary finding in childhood infection and inflammation. Primary hereditary thrombocytosis may be caused by germline mutations within the genes encoding key regulators of thrombopoiesis, i.e., thrombopoietin (THPO) and its receptor c-MPL (MPL) or the receptor’s effector kinase Januskinase2 (JAK2). Furthermore, somatic mutations in JAK2, MPL, and in the gene-encoding calreticulin (CALR) have been described to act as driver mutations within the so-called Philadelphia-negative myeloproliferative neoplasms (MPNs), namely essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). Increasing knowledge on the molecular mechanisms and on the clinical complications of these diseases is reflected by the WHO diagnostic criteria and European LeukemiaNet (ELN) recommendations on the management of adult MPN. However, data on childhood thrombocytosis are rare, and no consensus guidelines for pediatric thrombocytosis exist. Current literature has highlighted differences in the epidemiology and molecular pathogenesis of childhood thrombocytosis as compared to adults. Furthermore, age-dependent complications and pharmacological specificities suggest that recommendations tailored to the pediatric population are necessary in clinical practice. Here we summarize literature on classification, diagnostics, and clinical management of childhood thrombocytosis.

The most common causes of morbidity and mortality in myeloproliferative neoplasms (MPN) are thrombotic and hemorrhagic complications. The JAK2V617F mutation, commonly found in MPN, correlates with several clinical and laboratory characteristics even if the relevance of JAK2V617F allele burden in the natural history of these diseases is unclear. In this study we searched, a relation between thrombotic and hemorrhagic complications and JAK2V617F allele burden level in MPN patients. We evaluated 253 consecutive MPN [121 essential thrombocythemia (ET), 124 polycythemia vera (PV), and 8 primary myelofibrosis (PMF)] patients in whom the JAK2V617F allele burden was available, all studied and followed (median 8.8 years) in our department. Patients were stratified accordingly to their JAK2V617F allele burden, into four quartiles (1st25%, 2nd 26-50%, 3rd 51-75%, and 4th75%). Significantly higher incidence of thromboses (p = 0.001) and hemorrhages (p 0.001) during follow-up has been observed in higher quartiles when compared to lower ones. Thrombosis- and hemorrhage-free survivals were poorer in patients belonging to the highest quartile. Our data suggest that MPN patients with JAK2V617F allele burden higher than 75% have to be considered as high risk patients, being prone to develop thrombo-hemorrhagic complications during the disease course.

The telomerase reverse transcriptase (TERT) gene rs2736100_C allele has recently been shown to be associated with an increased risk for myeloproliferative neoplasms (MPNs) among Caucasians. However, it is unknown if this association is present in other ethnical populations and whether rs2736100 allele frequencies mirror the incidence of MPNs in a population. Here we genotyped TERT rs2736100 variants in 126 Swedish and 101 Chinese MPN patients and their age-, sex-, and ethnically-matched healthy controls. Healthy Chinese adults had a higher frequency of the A allele and lower frequencies of the C allele compared to Swedish counterparts (57.4 vs 47.0 % for A, 42.6 vs 53.0 % for C, P = 0.006). Both Swedish and Chinese patients harbored significantly higher C allele frequency than their controls (62.7 vs 53.0 % and 57.4 vs 42.6 % for Swedish and Chinese, respectively, P = 0.004). Swedes and Chinese bearing the CC genotype had a significantly increased risk of MPN compared to AA carriers (OR = 2.47; 95 % CI: 1.33–4.57, P = 0.003, for Swedes, and OR = 3.45; 95 % CI: 1.52–7.85, P = 0.005, for Chinese). Further analyses showed that rs2736100_CC was associated with robustly enhanced risk in males only (CC vs AA, OR = 5.11; 95 % CI: 2.19–11.92, P