Myelofibrosis (MF)

What Is Myelofibrosis? Myelofibrosis (MF) is a rare type of chronic blood cancer that originates in the bone marrow. In MF, healthy bone marrow tissue is gradually replaced by fibrous scar tissue, a process known as fibrosis. This scarring disrupts the bone marrow’s ability to produce normal blood cells, including red blood cells, white blood cells, and platelets. Myelofibrosis is usually a slow-growing disease, and many people live with it for years without noticeable symptoms. In some cases, however, MF progresses more rapidly and requires timely medical treatment. A hallmark feature of myelofibrosis is the overproduction of megakaryocytes — large bone marrow cells that normally produce platelets. In MF, these cells release excessive amounts of cytokines, proteins that promote inflammation. This chronic inflammation stimulates further scarring in the bone marrow, worsening blood cell production over time. Risk Factors for Myelofibrosis The exact cause of myelofibrosis is not fully understood. However, several factors are associated with an increased risk: Age: Most commonly diagnosed in people over 60 Environmental exposure: Ionizing radiation and petrochemicals such as benzene and toluene JAK2 mutation: Present in approximately 50–60% of MF patients; this mutation causes blood cells to grow and divide abnormally CALR mutation: Found in about 35% of people with MF Other genetic mutations may also play a role, although they are less common. Symptoms of Myelofibrosis Because MF often develops slowly, many patients experience no symptoms in the early stages. As the disease progresses and blood cell production becomes increasingly impaired, symptoms may include: Anemia, leading to fatigue, weakness, and shortness of breath Frequent infections Itching Pale skin Night sweats Fever Unexplained weight loss Abnormal bleeding or easy bruising Bone or joint pain Enlarged spleen (splenomegaly), causing discomfort or a feeling of fullness in the upper left abdomen Enlarged liver Dilated veins in the stomach or esophagus, which may rupture and bleed Portal hypertension, increased blood pressure in the vein connecting the spleen and liver Unexplained blood clots Extramedullary hematopoiesis, where blood-forming cells grow outside the bone marrow, potentially forming masses that compress organs or interfere with their function Types of Myelofibrosis Myelofibrosis is considered a rare form of chronic leukemia and is classified into two main types: Primary myelofibrosis: Occurs on its own, without a prior bone marrow disorder Secondary myelofibrosis: Develops as a complication of another bone marrow disease, such as polycythemia vera or essential thrombocythemia In approximately 12% of primary myelofibrosis cases, the disease can progress to acute myeloid leukemia (AML), a more aggressive and fast-growing cancer.