Primary myelofibrosis (PMF) is a rare myeloproliferative neoplasms (MPN) characterized by mutations in three driver genes that cause an hematopoietic stem cell – derived monoclonal proliferation: janus kinase 2 (JAK2), calreticulin (CALR) or MPL proto-oncogene (MPL) (83). The gene discussed is CALR; the disease is myeloproliferative disorder.