CALR and acquired polycythemia vera: General risk factors in MPNs associated with pathological bleedings include the use of aspirin and anticoagulants, disease phenotype (myelofibrosis>PV>essential thrombocythemia), extreme thrombocytosis (ie, >1 × 1000-1500 × 109/L), leukocytosis, higher JAK2 allele burden, the presence of calreticulin mutations, arterial hypertension, and male sex (21-23).