Myelofibrosis is associated with the presence of 3 cardinal and often mutually exclusive mutations: janus kinase 2 V617F (JAK2V617F), calreticulin (CALR) and myeloproliferative leukemia virus (MPL) oncogene.(2) Only 10% of patients are triple negative (no JAK2, CALR or MPL mutations). The gene discussed is CALR; the disease is myelofibrosis.