Scottsdale, Arizona - 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 an uncommon type of chronic leukemia - a cancer that affects the blood-forming tissues in the body. Myelofibrosis belongs to a group of diseases called myeloproliferative disorders.

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.

Myelofibrosis usually develops slowly. In its very early stages, many people don't experience signs or symptoms. But as disruption of normal blood cell production increases, signs and symptoms may include:

  • Feeling tired, weak or short of breath, usually because of anemia
  • Pain or fullness below your ribs on the left side, due to an enlarged spleen
  • Pale skin
  • Easy bruising
  • Easy bleeding
  • Excessive sweating during sleep (night sweats)
  • Fever
  • Frequent infections
  • Bone pain

When to see a doctor

Make an appointment with your doctor if you have any persistent signs and symptoms that worry you.

Myelofibrosis occurs when blood stem cells develop a genetic mutation. Blood stem cells have the ability to replicate and divide into the multiple specialized cells that make up your blood — red blood cells, white blood cells and platelets.

It's not clear what causes the genetic mutation in blood stem cells.

As the mutated blood stem cells replicate and divide, they pass along the mutation to the new cells. As more and more of these mutated cells are created, they begin to have serious effects on blood production.

The end result is usually a lack of red blood cells — which causes the anemia characteristic of myelofibrosis — and an overabundance of white blood cells with varying levels of platelets. In people with myelofibrosis, the normally spongy bone marrow becomes scarred.

The gene mutation that occurs in most people affected by myelofibrosis is sometimes referred to as JAK2. Other gene mutations also may be associated with myelofibrosis.