Primary myelofibrosis (PMF) is among the Philadelphia Chromosome Negative Myeloproliferative Disorders. This diagnosis can be present at a patient's initial diagnosis or it can arise out of preceding Polycythemia Vera or Essential Thrombocythemia. While the clinical course is variable, it is defined by varying degrees of splenomegaly, anemia, fatigue and other constitutional symptoms. Patients with PMF are at increased risk of acute leukemia, bone marrow failure and thrombosis. Currently, the only curative treatment for PMF is allogeneic stem cell transplant. However, as the median age at diagnosis is in the mid to late 60s, most patients are no longer candidates for transplant due to their age and/or other comorbid illnesses.