Idiopathic myelofibrosis

Alternative names 
Myelofibrosis; Primary myelofibrosis; Myeloid metaplasia; Agnogenic myeloid metaplasia

Primary myelofibrosis is a disorder of the bone marrow in which the marrow is replaced by fibrous (scar) tissue.

Causes, incidence, and risk factors

In primary myelofibrosis, a progressive scarring (fibrosis) of the bone marrow occurs. This causes blood formation to take place in sites other than the bone marrow, such as the liver and spleen, causing enlargement of these organs. The cause is unknown.

The disorder usually develops slowly, in people over 50 years old. It leads to progressive bone marrow failure with severe anemia. Low platelet count leads to easy bleeding, and spleen enlargement continues. The disease gets progressively worse in most cases. Risk factors are unknown.


  • Fatigue  
  • Abdominal fullness related to an enlarged spleen  
  • Easy bleeding  
  • Bone pain  
  • Pallor (paleness)  
  • Shortness of breath on exertion  
  • Bruising  
  • Increased susceptibility to infection

Signs and tests
Physical examination shows an enlarged spleen. Later in the disease, it may also show an enlarged liver.

  • An examination of the blood shows teardrop-shaped red blood cells.  
  • The white blood cell count is variable.  
  • The platelet count is variable.  
  • Bone marrow biopsy may be performed to rule out other causes of the symptoms.  
  • CBC (complete blood count) shows a low red blood cell count.

There is no specific treatment for primary myelofibrosis. Blood transfusions are given to correct anemia. Recombinant erythropoietin or androgens may stimulate red blood cell production and may be beneficial. A splenectomy (removal of the spleen) may help if the enlarged size of the spleen causes symptoms. Radiation and chemotherapy may also be used. In young people, bone marrow transplants appear to improve the outlook.

Expectations (prognosis)
The average survival of people with primary myelofibrosis is about 5 years. However, many people survive for decades. In the end stages, myelofibrosis is a wasting, debilitating illness.


  • Liver failure  
  • Acute myelogenous leukemia

Calling your health care provider
Call for an appointment with your health care provider if symptoms of this disorder develop. Uncontrolled bleeding, shortness of breath, jaundice, and progressive confusion are symptoms that indicate a need for urgent or emergency care.

There is no known prevention.

Johns Hopkins patient information

Last revised: December 8, 2012
by Armen E. Martirosyan, M.D.

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