According to the 2016 revision of the World Health Organization (WHO) classification, the diagnosis of ET is based on sustained thrombocytosis (platelet count ≥ 450 × 109/L), characteristic megakaryocytic proliferation in the bone marrow, exclusion of other myeloid neoplasms, and the presence of clonal markers such as mutations in Janus kinase 2 (JAK2), calreticulin (CALR), or the myeloproliferative leukemia virus oncogene (MPL) [1]. The gene discussed is JAK2; the disease is Thrombocytosis.