Primary myelofibrosis (PMF) is a clonal myeloproliferative neoplasm (MPN) stemming from hematopoietic stem and progenitor cells (HSPCs), frequently associated with mutations in Janus kinase signal transducer (JAK2), calreticulin (CALR), or thrombopoietin receptor (MPL). Here, JAK2 is linked to myeloproliferative disorder.