Myelofibrosis is a serious bone marrow disorder that disrupts your body's normal production of blood cells. The result is extensive scarring in your bone marrow, leading to severe anemia, weakness, fatigue, and often, an enlarged spleen and liver. Myelofibrosis is a type of chronic leukemia - a cancer that affects the blood-forming tissues in the body. Myelofibrosis can occur on its own (primary myelofibrosis) or it can occur as a result of another bone marrow disorder (secondary myelofibrosis). Many people with myelofibrosis get progressively worse, and some may eventually develop a more serious form of leukemia. Yet it's also possible to have myelofibrosis and live symptom-free for years. Treatment for myelofibrosis, which focuses on relieving symptoms, can involve a variety of options.