Myelofibrosis is a rare type of blood cancer that affects the bone marrow, leading to the formation of scar tissue. This scarring disrupts the production of blood cells, which can result in anemia, fatigue, and an enlarged spleen. The exact cause of myelofibrosis is often unknown, but it can be associated with mutations in certain genes, such as JAK2. Treatment options may include medications, blood transfusions, or in severe cases, a stem cell transplant to help restore normal blood cell production.