Pre-PMF emerging as important subgroup of MPN

In this issue of Blood , Guglielmelli et al highlight the importance of distinguishing prefibrotic/early primary myelofibrosis (pre-PMF) from overt primary myelofibrosis (overt-PMF) as a separate prodromal subgroup of myeloproliferative neoplasm (MPN). 1 Before the World Health Organization (WHO) 2016 classification, pre-PMF was neither generally accepted in the scientific community as a distinct subgroup of MPN nor aligned with overt-PMF. 2 In this study, the authors provide evidence that pre-PMF represents a prodromal stage of overt-PMF, and that it is clearly different from essential thrombocythemia (ET). With respect to clinical, hematologic, and molecular phenotypes, pre-PMF is associated with better risk factors that result in prolonged overall survival, as well as leukemia-free and fibrosis-free survival, when compared with overt-PMF. However, as has been reported in earlier studies, pre-PMF showed a significantly shorter overall survival than ET. 3-5 Patients with pre-PMF are younger compared with patients with overt-PMF. Patients with overt-PMF have greater hematologic abnormalities (anemia, leukopenia, thrombocytopenia, higher blast counts), are more symptomatic, have larger spleens, and have a higher frequency of high molecular risk mutation profiles. Interestingly, the cohort of patients with pre-PMF had a predominance of female patients, which suggests the possibility that male patients progress to overt-PMF faster as the sex distribution is balanced in the later cohort.