Literature Review: Essential Thrombocythemia
Nichola H Lawrence, Indu Singh, Michelle Butina, Nicola Richards
Int. J. Bio. Lab. Sci 2021(10)2:91-101【PDF】

Abstract
Essential Thrombocythemia (ET), a clonal hematopoietic stem cell disorder, is one of the classic Philadelphia negative myeloproliferative neoplasms and is characterized by thrombocytosis with bone marrow megakaryocytic hyperplasia. Mutations in Janus kinase 2 (JAK2), calreticulin (CALR), or myeloproliferative leukemia (MPL) are found in approximately 80-90% of patients. Over the past decade, new molecular and clinical knowledge in ET has led to a significant improvement in the diagnostic, prognostic, and therapeutic processes. Despite these advancements, many uncertainties remain regarding clinical decision-making. In the 2016 revised World Health Organization (WHO) classification true ET requires meeting all 4 major criteria described below or 3 major criteria and one minor criterion. Because of the revised WHO classification, study data has been re-evaluated and the revised International Prognostic Score of Thrombosis for Essential Thrombocythemia risk stratification was devised allowing clinicians to assign patients to the appropriate risk group in a 4-tiered system. In ET patient’s transformation to acute myeloid leukemia and/or post-ET myelofibrosis are rare events. Current treatment in ET is primarily indicated for the purposes of preventing vascular complications which have been reported to be the leading cause of death. Thrombotic complications can occur in up to 24% of patients with 13% developing a vascular event before diagnosis. Mutational status has an impact on thrombotic risk with a lower rate of thrombosis seen in CALR-mutants as compared to JAK2 V617F/MPL mutants and triple-negative cases. Mutations other than JAK2, CALR, or MPL have been found in approximately 53% of patients with ET with the most frequent being TET2, ASXL1, DNMT3A, and SF3B1.

Key words: Essential Thrombocythemia, JAK2 mutation, CALR mutation, MPL mutation, Platelets.