A serious bone marrow condition that harms the making of blood cells.

Myelofibrosis is a serious bone marrow condition that harms the body's ability to make blood cells. It causes scarring, also called fibrosis, in the bone marrow. Myelofibrosis is a type of chronic leukemia.

Myelofibrosis develops slowly. There may be no symptoms at first. Symptoms may include feeling weak and very tired. Other symptoms may include an enlarged spleen and liver.

Treatments depend on the risk level. Treatment may not be needed for low-risk disease. A bone marrow transplant may be used for people at high risk. Treatments usually manage symptoms for those at medium risk.