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Chronic Myeloproliferative Disorders

To view this article in the new Rare Cancers Australia Knowledgebase, click here 

Definition of myeloproliferative disorders:

A type of disease in which the bone marrow makes too many red blood cells, platelets, or certain white blood cells.

Myeloproliferative disorders usually get worse over time as the number of extra cells build up in the blood and/or bone marrow. This may cause bleeding problems, anemia, infection, fatigue, or other signs and symptoms. Certain myeloproliferative disorders may become acute myeloid leukemia (AML). Myeloproliferative disorders include chronic myelogenous leukemia (CML), polycythemia vera, primary myelofibrosis, essential thrombocythemia, chronic neutrophilic leukemia, and chronic eosinophilic leukemia. Also called chronic myeloproliferative disorder

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

Normally, the bone marrow makes blood stem cells (immature cells) that become mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell. A lymphoid stem cell becomes a white blood cell. A myeloid stem cell becomes one of three types of mature blood cells:

  • Red blood cells that carry oxygen and other substances to all tissues of the body.
  • White blood cells that fight infection and disease.
  • Platelets that form blood clots to stop bleeding.

Blood cell development; drawing shows the steps a blood stem cell goes through to become a red blood cell, platelet, or white blood cell.  Drawing shows a myeloid stem cell becoming a red blood cell, platelet, or myeloblast, which then becomes a white blood cell. Drawing also shows a lymphoid stem cell becoming a lymphoblast and then one of several different types of white blood cells.

Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.

In myeloproliferative disorders too many blood stem cells become one or more types of blood cells. The disorders usually get worse slowly as the number of extra blood cells 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.
  • Primary myelofibrosis (also called 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.

Myelosclerosis with Myeloid Metaplasia

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 primary myelofibrosis.

Essential Thrombocythaemia (ET)

Essential thrombocythaemia (ET) is a disorder in which too many platelets are produced in the bone marrow. Platelets are normally needed in the body to control bleeding. However, excess numbers of platelets can lead to abnormal blood clotting which can block the flow of blood in the blood vessels.

There are a number of conditions that can cause a rise in the number of platelets in the circulating blood (thrombocytosis). These include bleeding, infection and some types of cancer. In essential thrombocythaemia however, the blood platelet count is persistently elevated as a result of increased bone marrow production of platelets, in the absence of any identifiable cause.

Essential thrombocythaemia is a rare chronic disease diagnosed in an estimated 3 per 100,000 population. Although it can occur at any age, even (rarely) in children, essential thrombocythaemia usually affects older people, with most patients diagnosed between the ages of 50 and 70 years. It occurs equally in both males and females.

Polycythaemia (Rubra) Vera

Polycythaemia (Rubra) Vera, also known as primary polycythaemia vera, is a disorder where too many red cells are produced in the bone marrow, without any identifiable cause. These cells accumulate in the bone marrow and in the blood stream where they increase the blood volume and cause the blood to become thicker, or more 'viscous' than normal. In many people with polycythaemia vera, too many platelets and white cells are also produced.

Polycythaemia vera is a rare chronic disease diagnosed in an estimated 2 to 3 people per 100,000 population. Although it can occur at any age, polycythaemia vera usually affects older people, with most patients diagnosed over the age of 55 years. Polycythaemia vera is rare in children and young adults. It occurs more commonly in males than in females.

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.

Complete blood count (CBC); left panel shows blood being drawn from a vein on the inside of the elbow using a tube attached to a syringe; right panel shows a laboratory test tube with blood cells separated into layers: plasma, white blood cells, platelets, and red blood cells. 

Complete blood count (CBC). Blood is collected by inserting a needle into a vein and allowing the blood to flow into a tube. The blood sample is sent to the laboratory and the red blood cells, white blood cells, and platelets are counted. The CBC is used to test for, diagnose, and monitor many different conditions.

  • Peripheral blood smear: A procedure in which a sample of blood is checked for the following:
    • Whether there are red blood cells shaped like teardrops.
    • The number and kinds of white blood cells.
    • The number of platelets.
    • Whether there are blast cells.
  • Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it.
  • Bone marrow aspiration and biopsy: The removal of bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for abnormal cells.

Bone marrow aspiration and biopsy; drawing shows a patient lying face down on a table and a Jamshidi needle (a long, hollow needle) being inserted into the hip bone. Inset shows the Jamshidi needle being inserted through the skin into the bone marrow of the hip bone.

Bone marrow aspiration and biopsy. After a small area of skin is numbed, a Jamshidi needle (a long, hollow needle) is inserted into the patient’s hip bone. Samples of blood, bone, and bone marrow are removed for examination under a microscope.

  • 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.
  • JAK2 gene mutation test: A laboratory test done on a bone marrow or blood sample to check for a JAK2 gene mutation. A JAK2 gene mutation is often found in patients with polycythemia vera, essential thrombocythemia, or idiopathic myelofibrosis.

For more information on Chronic Myeloproliferative Disorders click here

This link is to the National Cancer Institute (NCI) cancer website in the United States. There may be references to drugs and clinical trials that are not available here in Australia.

Information has been sourced from leukaemia.org.au and cancer.gov

For information about clinical trials that are available in Australia click here

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