CD34 and myeloproliferative disorder: Primary myelofibrosis (PMF) is a Philadelphia-negative (Ph−) myeloproliferative disorder of unknown aetiology, characterized by the presence of acquired mutations of either JAK2, or MPL, or CALR genes in the myeloid cells of 90% of the patients [1], abnormal CD34+ progenitor cell trafficking [2], splenomegaly, and marrow fibrosis leading to extensive extramedullary haematopoiesis [3].