JAK2 and myeloproliferative disorder: Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm characterized by the presence of clonal proliferation of myeloid cells in the bone marrow (BM) led by driver mutations, which include JAK2, MPL and CALR, that induce disease phenotype most notably by the activation of the JAK‐STAT pathway [1, 2].