Myeloproliferative Disorders
Myeloproliferative disorders are a group of blood diseases characterized by chronic increases in some or all of the blood cells. This group of blood disorders includes
- Polycythemia vera
- Essential (or primary) thrombocythemia
- Idiopathic myelofibrosis
Polycythemia vera is a disease in which the red cells are the main cells that are increased beyond normal levels. In many patients, white blood cell and platelets counts are also elevated.
Complications result mainly from the increase in red cells and in platelets: too many red blood cells make it difficult for the blood to flow smoothly; too many platelets can lead to the formation of blood clots; and underlying vascular disease, commonly found in older people, can increase the risk of serious complications, such as strokes or heart attacks.
Essential (or primary) thrombocythemia is a disease in which the platelets are the main cells that are increased beyond normal levels.
The normal formation of platelets consists of stem cells forming a few very large cells in the marrow called megakaryocytes. Each of the megakaryocytes generates hundreds or thousands of platelets. In essential thrombocythemia, the altered stem cells produce an excessive number of megakaryocytes. The end result is abnormally high levels of platelets in the blood. When present in very large numbers, these platelets may not function normally and can cause blockages in blood vessels or bleeding problems.
Idiopathic myelofibrosis is a disease in which scar-like tissue forms in the marrow as a result of abnormal production of red cells, white cells, and platelets.
Too few red cells are made, and usually too many white cells and megakaryocytes. The excessive production of megakaryocytes leads to abnormally high levels of platelets in the blood. The overproduction of abnormal megakaryocytes also releases chemicals in the marrow that lead to the production of fibrous (scar-like) tissue in the marrow.
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.
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.
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 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 for information on diagnosis, staging, and treatment.
Information Obtained From National Institute Of Health