Myelofibrosis (MF) is a chronic blood cancer in which abnormal or malignant precursor cells in the bone marrow proliferate rapidly, causing scar tissue to form (fibrosis). As a result, normal blood production in the bone marrow is impaired and may shift to other organs such as the spleen and liver, which can cause them to enlarge substantially. People with MF may have abnormally low or high numbers of circulating red blood cells, white blood cells or platelets, and abnormally high numbers of immature cells in the blood or bone marrow. MF patients can also suffer from debilitating constitutional symptoms, such as drenching night sweats, fatigue, severe itching (pruritus), abdominal pain, fever and bone pain.
MF is classified as a myeloproliferative neoplasm (MPN) and can arise on its own (primary myelofibrosis, PMF), or as a progression of polycythemia vera (post-PV-MF) or essential thrombocythemia (post-ET-MF). The manifestations of PMF, post-PV-MF and post-ET-MF are virtually identical and treatment is generally the same for all three.
The number of people living with MF in the United States is estimated at 13,000 patients, with approximately 3,000 new cases diagnosed each year. Up to 20% of patients with MF develop acute myeloid leukemia (AML).