Primary Myelofibrosis

This chapter illustrates the diagnosis and treatment of primary myelofibrosis (PMF), a myeloproliferative neoplasm (MPN). PMF is diagnosed according to a 2008 World Health Organization system. This disorder is characterized by stem cell-derived clonal myeloproliferation and the presence of somatic mutations involving JAK2 (in the majority of patients) and MPL or other somatic mutations (in the minority). Current prognostication in PMF is best accomplished by the use of the International Prognostic Scoring System (IPSS), dynamic IPSS (DIPSS), or DIPSS-plus. High-risk or intermediate-2 risk patients with PMF should always be considered for either investigational drug therapy or allogeneic hematopoietic cell transplant. Ruxolitinib, a JAK1-JAK2 inhibitor, is used in patients with high-or intermediate-risk disease. In general, allogeneic stem cell transplant is a treatment modality whose benefits should be carefully balanced against its risks. Pomalidomide, other JAK-inhibiting adenosine triphosphate (ATP) mimetics, and other novel drugs (e.g., mTOR inhibitors) are currently being tested in patients with MF.