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Chronic Myeloproliferative Disorders Treatment (PDQ®)

Patient Version
Last Modified: 09/27/2011

Primary Myelofibrosis

Key Points for This Section


Primary myelofibrosis is a disease in which abnormal blood cells and fibers build up inside the bone marrow.

The bone marrow is made of tissues that make blood cells (red blood cells, white blood cells, and platelets) and a web of fibers that support the blood-forming tissues. In primary myelofibrosis (also called chronic idiopathic myelofibrosis), large numbers of blood stem cells develop into blood cells that do not mature properly (blasts). The web of fibers inside the bone marrow also becomes very thick (like scar tissue) and slows the blood-forming tissue’s ability to make blood cells. This causes the blood-forming tissues to make fewer and fewer blood cells. In order to make up for the low number of blood cells made in the bone marrow, the liver and spleen begin to make the blood cells.

Possible signs of primary myelofibrosis include pain below the ribs on the left side and feeling very tired.

Primary myelofibrosis often does not cause early symptoms. It is sometimes found during a routine blood test. The following symptoms may be caused by primary myelofibrosis or by other conditions. A doctor should be consulted if any of these problems occur:

  • Feeling pain or fullness below the ribs on the left side.
  • Feeling full sooner than normal when eating.
  • Feeling very tired.
  • Shortness of breath.
  • Easy bruising or bleeding.
  • Petechiae (flat, red, pinpoint spots under the skin that are caused by bleeding).
  • Fever.
  • Night sweats.
  • Weight loss.

A special blood test is used to diagnose primary myelofibrosis.

In addition to a complete blood count, bone marrow aspiration and biopsy, and cytogenetic analysis, a peripheral blood smear is used to diagnose primary myelofibrosis. A peripheral blood smear is a procedure in which a sample of blood is checked for tear drop-shaped red blood cells, the number and kinds of white blood cells, the number of platelets, and the presence of blast cells.

Certain factors affect prognosis (chance of recovery) and treatment options for primary myelofibrosis.

Prognosis (chance of recovery) depends on the following:

  • The age of the patient.
  • The number of abnormal red blood cells and white blood cells.
  • The number of blasts in the blood.
  • Whether there are certain changes in the chromosomes.
  • Whether the patient has symptoms such as fever, night sweats, or weight loss.


Glossary Terms

abnormal (ab-NOR-mul)
Not normal. An abnormal lesion or growth may be cancer, premalignant (likely to become cancer), or benign (not cancer).
blast (blast)
An immature blood cell.
blood (blud)
A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.
bone marrow (bone MAYR-oh)
The soft, sponge-like tissue in the center of most bones. It produces white blood cells, red blood cells, and platelets.
bone marrow aspiration (bone MAYR-oh AS-pih-RAY-shun)
A procedure in which a small sample of bone marrow is removed, usually from the hip bone, breastbone, or thigh bone. A small area of skin and the surface of the bone underneath are numbed with an anesthetic. Then, a special wide needle is pushed into the bone. A sample of liquid bone marrow is removed with a syringe attached to the needle. The bone marrow is sent to a laboratory to be looked at under a microscope. This procedure may be done at the same time as a bone marrow biopsy.
bone marrow biopsy (bone MAYR-oh BY-op-see)
A procedure in which a small sample of bone with bone marrow inside it is removed, usually from the hip bone. A small area of skin and the surface of the bone underneath are numbed with an anesthetic. Then, a special, wide needle is pushed into the bone and rotated to remove a sample of bone with the bone marrow inside it. The sample is sent to a laboratory to be looked at under a microscope. This procedure may be done at the same time as a bone marrow aspiration.
cell (sel)
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
chromosome (KROH-muh-some)
Part of a cell that contains genetic information. Except for sperm and eggs, all human cells contain 46 chromosomes.
complete blood count (kum-PLEET blud kownt)
A test to check the number of red blood cells, white blood cells, and platelets in a sample of blood. Also called blood cell count and CBC.
cytogenetics (SY-toh-jeh-NEH-tix)
The study of chromosomes and chromosomal abnormalities.
diagnosis (DY-ug-NOH-sis)
The process of identifying a disease, such as cancer, from its signs and symptoms.
liver (LIH-ver)
A large organ located in the upper abdomen. The liver cleanses the blood and aids in digestion by secreting bile.
peripheral blood smear (peh-RIH-feh-rul blud smeer)
A procedure in which a sample of blood is viewed under a microscope to count different circulating blood cells (red blood cells, white blood cells, platelets, etc.) and see whether the cells look normal.
petechiae (peh-TEE-kee-ee)
Pinpoint, unraised, round red spots under the skin caused by bleeding.
platelet (PLAYT-let)
A tiny piece of a cell found in the blood that breaks off from a large cell found in the bone marrow. Platelets help wounds heal and prevent bleeding by forming blood clots. Also called thrombocyte.
primary myelofibrosis (PRY-mayr-ee MY-eh-loh-fy-BROH-sis)
A progressive, chronic disease in which the bone marrow is replaced by fibrous tissue and blood is made in organs such as the liver and the spleen, instead of in the bone marrow. This disease is marked by an enlarged spleen and progressive anemia. Also called agnogenic myeloid metaplasia, chronic idiopathic myelofibrosis, idiopathic myelofibrosis, and myelosclerosis with myeloid metaplasia.
prognosis (prog-NO-sis)
The likely outcome or course of a disease; the chance of recovery or recurrence.
red blood cell (red blud sel)
A cell that carries oxygen to all parts of the body. Also called erythrocyte and RBC.
spleen (spleen)
An organ that is part of the lymphatic system. The spleen makes lymphocytes, filters the blood, stores blood cells, and destroys old blood cells. It is located on the left side of the abdomen near the stomach.
stem cell (stem sel)
A cell from which other types of cells develop. For example, blood cells develop from blood-forming stem cells.
symptom (SIMP-tum)
An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.
tissue (TIH-shoo)
A group or layer of cells that work together to perform a specific function.
white blood cell (hwite blud sel)
A type of immune cell. Most white blood cells are made in the bone marrow and are found in the blood and lymph tissue. White blood cells help the body fight infections and other diseases. Granulocytes, monocytes, and lymphocytes are white blood cells. Also called leukocyte and WBC.