Absence of JAK2V617F mutation in patients with betathalassemia major and thrombocytosis due to splenectomy

Thalassemia Unit, Hippokration Hospital, Thessaloniki, Greece.
Molecular Biology Reports (Impact Factor: 2.02). 12/2011; 39(5):6101-5. DOI: 10.1007/s11033-011-1425-7
Source: PubMed


The report of Janus Kinase 2 (JAK2) mutations in myeloid malignancies with high frequency in myeloproliferative neoplasms has been well known since 2005. By monitoring allele burden, it is found that the expression of JAK2V617F mutation is increasing significantly from essential thrombocytosis to polycythemia vera. Furthermore, JAK2 abnormalities are reported in the majority of unexplained thrombotic episodes. Thalassemic syndromes are characterized by ineffective erythropoiesis and thrombocytosis, mainly due to splenectomy. The high incidence of thromboembolic events has led to the identification of a prothrombotic state in these patients. The contribution of JAK2 mutations to the hypercoagulable state of thalassemic patients is still unknown. Furthermore, the potential role of Janus Kinase mutations in hepcidin expression and consequently in ineffective erythropoiesis is still under investigation. This study was scheduled to determine whether the presence of JAK2V617F mutation in thalassemic patients is associated with thrombocytosis. We studied 20 patients DNA with beta-thalassemia for JAK2V617F mutation by using RG-PCR method. None of the patients were positive for this particular mutation. More studies are needed to prove the role of JAK2 in ineffective erythropoiesis, iron metabolism and thrombocytosis and to determine if using JAK2 inhibitors in thalassemic patients can be a potential therapeutic option.

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    ABSTRACT: : The identification of Jak2(V617F) mutations in more than 90% of patients with polycythemia vera (PV) has greatly improved the diagnostic accuracy for this uncommon myeloproliferative disorder. Although previous cases of presumptive PV in patients with hereditary spherocytosis (HS) have been described, these earlier reports either preceded the establishment of widely accepted criteria for the diagnosis of PV or lacked definitive studies to rule out secondary causes of polycythemia. In contrast, the author describes here a novel case of PV confirmed at the molecular level in a patient with hereditary spherocytosis by the finding of a Jak2(V617F) mutation. Based on recent advances in understanding the role of Jak2 signaling in the pathogenesis of PV, the author proposes 2 independent biological mechanisms that could account for more than a chance association of these 2 disorders.
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    ABSTRACT: Thrombosis is a major complication of polycythemia vera (PV) and also a well-known complication of thalassemia. We reported a case of non-atherosclerotic ST-segment elevation myocardial infarction (STEMI) in a 17- year-old man with concurrent post-splenectomized hemoglobin H-Constant Spring disease and JAK2 V617F mutation-positive PV. The patient initially presented with extreme thrombocytosis (platelet counts greater than 1,000,000/μL) and three months later developed an acute STEMI. Coronary artery angiography revealed an acute clot in the right coronary artery without atherosclerotic plaque. He was treated with plateletpheresis, hydroxyurea and antiplatelet agents. The platelet count decreased and his symptoms improved. This case represents the importance of early diagnosis, awareness of the increased risk for thrombotic complications, and early treatment of PV in patients who have underlying thalassemia with marked thrombocytosis.
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