Myelofibrosis

In myelofibrosis, fibrous tissue in the bone marrow grows too much and crowds out the immature cells (called stem cells) that develop into blood cells.

Myelofibrosis is rare. It usually affects people between the ages of 50 and 70.

Anemia develops and worsens progressively. Many of the red blood cells in the blood are immature or misshapen. White blood cells and platelets may also be immature. As myelofibrosis progresses, the white blood cell count may increase or decrease, and the platelet count typically decreases. The liver and spleen often enlarge as they make more blood cells. Thus, they try to compensate for the inadequate production of blood cells in the bone marrow.

This disorder often results in death in 3 to 5 years. However, for some people, stem cell transplantation cures the disorder.

Causes

The cause of myelofibrosis may be unknown. In such cases, it is called idiopathic. Myelofibrosis may accompany other blood disorders, such as chronic myelocytic leukemia, polycythemia vera, thrombocythemia, multiple myeloma, and lymphoma. It may also accompany tuberculosis or bone infections. Exposure to certain toxic substances, such as benzene and radiation, increases the risk of developing myelofibrosis.

Symptoms and Diagnosis

Many people have no symptoms for years. As the anemia becomes more severe, people feel weak, tired, and generally unwell. They may lose weight and have a low-grade fever and night sweats. They are more likely to get infections because the white blood cell count is low. They are more likely to bleed because the platelet count is low.

The abdomen may feel uncomfortably full or pain may occur because the liver and spleen enlarge. Blood pressure in veins of the liver may become abnormally high (a disorder called portal hypertension). Varicose veins in the esophagus may bleed (a disorder called esophageal varices).

Myelofibrosis is suspected when a person has anemia and when the red blood cells, viewed under a microscope, are misshapen and immature. However, a bone marrow biopsy is needed to confirm the diagnosis.

Treatment and Outlook

Stem cell transplantation is the only treatment available that may cure myelofibrosis. But because this treatment is so taxing, it is rarely recommended for people over 75. People who are younger than 75 and who are in otherwise good health can undergo this treatment if an appropriate donor is available. Usually, stem cells are removed from bone marrow in the donor's hip bone with a syringe after the donor is given a general anesthetic. Sometimes stem cells can be obtained from blood. Five years after treatment, about half of people who receive a transplant are alive, and about one fourth have no sign of the disorder. However, transplantation has significant risks, such as graft-versus-host disease, serious infections, and death.

Other treatments may be able to delay or relieve symptoms. The combination of male sex hormones (androgens) and the corticosteroid prednisone lessens the severity of the anemia in about one third of people with myelofibrosis, but the effect lasts for only 6 to 18 months. However, men who have prostate cancer cannot take male sex hormones. In women, these hormones may have masculinizing side effects, such as a lower voice and increased body hair.

Alternatively, blood transfusions are used to treat the anemia. Erythropoietin (a synthetic version of the hormone produced by the body) or darbepoietin are effective in a few people. These drugs stimulate the bone marrow to produce red blood cells. Infections are treated with antibiotics.

The chemotherapy drug hydroxyurea or interferon-alpha (a drug that affects the immune system) may reduce the size of the liver or spleen. However, either drug may worsen the anemia, because they suppress production of blood cells. Rarely, when the spleen becomes extremely large and painful, it is removed or treated with radiation therapy.

On average, people with myelofibrosis live 3 to 5 years after the disorder is diagnosed. Some people live only a year or two. People who are older than 70, have severe anemia, have an enlarged liver, or lose weight do less well. Having a very high or very low white blood cell count or a very low platelet count is also likely to shorten life. Because myelofibrosis is progressive, people who have it should decide on and write down advance directives.