Chronic Myeloproliferative Disorders

by National Cancer Institute

General Information About Chronic Myeloproliferative Disorders

Myeloproliferative disorders are a group of diseases in which the bone marrow produces too many red blood cells, white blood cells, or platelets.

Normally, the bone marrow makes stem cells (immature blood cells) that develop into mature blood cells. There are 3 types of mature blood cells:

• Red blood cells that carry oxygen and other materials to all tissues of the body.
• White blood cells that fight infection and disease.
• Platelets that help prevent bleeding by causing blood clots to form.

Myeloproliferative disorders begin in the bone marrow and may cause a greater than normal number of stem cells to develop into one or more types of blood cells. The disorders usually get worse slowly as the number of extra blood cells slowly increases.

There are 6 types of chronic myeloproliferative disorders.

The type of myeloproliferative disorder is based on whether too many red blood cells, white blood cells, or platelets are being made. Sometimes the body will make too many of more than one type of blood cell, but usually one type of blood cell is affected more than the others are. Chronic myeloproliferative disorders include the following 6 types:

• Chronic myelogenous leukemia.
• Polycythemia vera.
• Chronic idiopathic myelofibrosis.
• Essential thrombocythemia.
• Chronic neutrophilic leukemia.
• Chronic eosinophilic leukemia.

These types are described below. Chronic myeloproliferative disorders sometimes become acute leukemia, in which too many abnormal white blood cells are made.

Tests that examine the blood and bone marrow are used to detect (find) and diagnose chronic myeloproliferative disorders.

The following tests and procedures may be used:

Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.

Complete blood count (CBC) with differential: A procedure in which a sample of blood is drawn and checked for the following:

• The number of red blood cells and platelets.
• The number and type of white blood cells.
• The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
• The portion of the blood sample made up of red blood cells.

Bone marrow aspiration and biopsy: The removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist views both the bone and the bone marrow samples under a microscope to look for signs of cancer.

Cytogenetic analysis: A test in which cells in a sample of blood or bone marrow are viewed under a microscope to look for certain changes in the chromosomes. Certain diseases or disorders may be diagnosed or ruled out based on the chromosomal changes.

Chronic Myelogenous Leukemia

Chronic myelogenous leukemia is a disease in which too many white blood cells are made in the bone marrow. Refer to the PDQ summary on Chronic Myelogenous Leukemia Treatment 1 for information on diagnosis, staging, and treatment.

Polycythemia Vera

Polycythemia vera is a disease in which too many red blood cells are made in the bone marrow.

In polycythemia vera, the blood becomes thickened with too many red blood cells. The number of white blood cells and platelets may also increase. These extra blood cells may collect in the spleen and cause it to swell. The increased number of red blood cells or platelets in the blood can cause bleeding problems and make clots form in blood vessels. This can cause serious health problems such as stroke or heart attack. In patients older than 65 years, the risk of stroke and heart attack is higher, and polycythemia vera is more likely to become acute myeloid leukemia or chronic idiopathic myelofibrosis.

Possible signs of polycythemia vera include headaches and a feeling of fullness below the ribs on the left side.

Polycythemia vera often does not cause early symptoms. It is sometimes found during a routine blood test. Symptoms may occur as the number of blood cells increases. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:

• A feeling of pressure or fullness below the ribs on the left side.
• Headaches.
• Double vision or seeing dark or blind spots that come and go.
• Itching all over the body, especially after being in warm or hot water.
• Reddened face that looks like a blush or sunburn.
• Weakness.
• Dizziness.
• Weight loss for no known reason.

Special blood tests are used to diagnose polycythemia vera.

In addition to a complete blood count, other special blood tests are used to diagnose polycythemia vera. These tests include the following:

Arterial blood gas (ABG) test: A test in which a sample of blood is taken from an artery to measure the amount of oxygen and carbon dioxide in the blood and the pH (acidity) of the blood.

Serum erythropoietin test: A test in which a sample of blood is checked for the level of erythropoietin (a hormone that stimulates new red blood cells to be made).

Leukocyte alkaline phosphatase (LAP) test: A test in which a sample of blood is checked to measure the amount of alkaline phosphatase (an enzyme) in leukocytes (white blood cells).

About the Author

www.nci.nih.gov
The National Cancer Institute's research programs are extensive and contain many innovative initiatives. I invite you to explore our Web site to find out more about the exciting work being conducted here at NCI and by NCI-supported scientists throughout the country.