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. 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.
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). 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. 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.
- JAK2genemutation 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.