Thrombocytopenia occurs when the bone marrow makes too few platelets or when too many platelets are destroyed or accumulate within an enlarged spleen.
Bleeding in the skin and bruising occur.
Doctors use blood tests to make the diagnosis and determine the cause.
Sometimes treatment (such as platelet transfusion, prednisone and drugs to increase platelet production, or removal of the spleen) is needed.
(See also Overview of Platelet Disorders Overview of Platelet Disorders Platelets (sometimes called thrombocytes) are cell fragments produced in the bone marrow that circulate in the bloodstream and help blood to clot. Thrombopoietin, primarily produced in the liver... read more .)
Platelets are cells produced in the bone marrow that circulate in the bloodstream and help blood clot How Blood Clots Hemostasis is the body's way of stopping injured blood vessels from bleeding. Hemostasis includes clotting of the blood. Too little clotting can cause excessive bleeding from minor injury Too... read more . The blood usually contains about 140,000 to 440,000 platelets per microliter (140 to 440 × 109 per liter). When the platelet count falls below about 50,000 platelets per microliter of blood (50 × 109 per liter), bleeding can occur even after relatively minor injury. The most serious risk of bleeding, however, generally does not occur until the platelet count falls below 10,000 to 20,000 platelets per microliter of blood (10 to 20 × 109 per liter). At these very low levels, bleeding may occur without any recognized injury.
Causes of Thrombocytopenia
Many disorders can cause thrombocytopenia, but these disorders fall into three main categories:
Too few platelets are produced
Too many platelets are destroyed
Too many platelets trapped in the spleen
Thrombocytopenia can occur when the bone marrow does not produce enough platelets, as happens in leukemia Overview of Leukemia Leukemias are cancers of white blood cells or of cells that develop into white blood cells. White blood cells develop from stem cells in the bone marrow. Sometimes the development goes awry... read more or other bone marrow disorders.
Infection with hepatitis C virus Overview of Hepatitis Hepatitis is inflammation of the liver. (See also Overview of Acute Viral Hepatitis and Overview of Chronic Hepatitis.) Hepatitis is common throughout the world. Hepatitis can be Acute (short-lived) read more , the human immunodeficiency virus Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more (HIV, the virus that causes acquired immunodeficiency syndrome [AIDS]), Epstein-Barr virus (the usual cause of mononucleosis Infectious Mononucleosis Epstein-Barr virus causes a number of diseases, including infectious mononucleosis. The virus is spread through kissing. Symptoms vary, but the most common are extreme fatigue, fever, sore throat... read more ), and many other viruses may result in thrombocytopenia.
Platelets can become entrapped in an enlarged spleen, as happens in cirrhosis of the liver Cirrhosis of the Liver Cirrhosis is the widespread distortion of the liver's internal structure that occurs when a large amount of normal liver tissue is permanently replaced with nonfunctioning scar tissue. The scar... read more , myelofibrosis Myelofibrosis Myelofibrosis is a disorder in which fibrous tissue in the bone marrow replaces the blood-producing cells, resulting in abnormally shaped red blood cells, anemia, and an enlarged spleen. Myelofibrosis... read more , and Gaucher disease Gaucher Disease Gaucher disease is a type of lysosomal storage disorder called a sphingolipidosis. It is caused by a buildup of glucocerebrosides in tissues. Children who have the infantile form usually die... read more , reducing the number of platelets in the bloodstream.
Massive red blood cell transfusions can dilute the concentration of platelets in the blood.
Finally, the body may use or destroy too many platelets, as occurs in many disorders, three of the most notable being immune thrombocytopenia Immune Thrombocytopenia (ITP) Immune thrombocytopenia (ITP) is a bleeding disorder caused by decrease in the number of platelets (thrombocytes) that occurs in a person who does not have another disorder that affects platelets... read more , thrombotic thrombocytopenic purpura Thrombotic Thrombocytopenic Purpura (TTP) Thrombotic thrombocytopenic purpura (TTP) is a serious disorder that involves the formation of small blood clots throughout the body that block the flow of blood to vital organs such as the... read more , and hemolytic-uremic syndrome Hemolytic-Uremic Syndrome (HUS) Hemolytic-uremic syndrome (HUS) is a serious disorder that usually occurs in children and involves the formation of small blood clots throughout the body that block the flow of blood to vital... read more .
Some drugs such as heparin, certain antibiotics, ethanol, anticancer drugs, and quinine can also cause thrombocytopenia. Drug-induced cytopenia may be the result of
Decreased platelet production by the bone marrow (caused by bone marrow toxicity)
Increased platelet destruction (immune-mediated thrombocytopenia)
Symptoms of Thrombocytopenia
Bleeding in the skin may be the first sign of a low platelet count. Many tiny red dots (petechiae) often appear in the skin on the lower legs, and minor injuries may cause bruises (ecchymoses or purpura). The gums may bleed, and blood may appear in the stool or urine. Menstrual periods may be unusually heavy. Bleeding may be hard to stop.
Bleeding worsens as the number of platelets decreases. People who have very few platelets may lose large amounts of blood into their digestive tract or may develop life-threatening bleeding in their brain even though they have not been injured.
The rate at which symptoms develop can vary depending on the cause and severity of thrombocytopenia.
Diagnosis of Thrombocytopenia
Blood tests to measure platelet count and clotting
Other tests for disorders that may cause a low platelet count
Doctors suspect thrombocytopenia in people who have abnormal bruising and bleeding or petechiae. They often check the number of platelets routinely in people who have disorders that might cause thrombocytopenia. Sometimes they discover thrombocytopenia when blood tests are done for other reasons in people who have no bruising or bleeding.
Determining the cause of thrombocytopenia is critical to treating the condition. Certain symptoms may help determine the cause. For example, people usually have a fever when thrombocytopenia results from an infection. In contrast, they usually do not have a fever when the cause is immune thrombocytopenia Immune Thrombocytopenia (ITP) Immune thrombocytopenia (ITP) is a bleeding disorder caused by decrease in the number of platelets (thrombocytes) that occurs in a person who does not have another disorder that affects platelets... read more , thrombotic thrombocytopenic purpura Thrombotic Thrombocytopenic Purpura (TTP) Thrombotic thrombocytopenic purpura (TTP) is a serious disorder that involves the formation of small blood clots throughout the body that block the flow of blood to vital organs such as the... read more , or hemolytic-uremic syndrome Hemolytic-Uremic Syndrome (HUS) Hemolytic-uremic syndrome (HUS) is a serious disorder that usually occurs in children and involves the formation of small blood clots throughout the body that block the flow of blood to vital... read more .
An enlarged spleen Enlarged Spleen An enlarged spleen is not a disease in itself but the result of an underlying disorder. Many disorders can make the spleen enlarge. Many disorders, including infections, anemias, and cancers... read more , which a doctor may be able to feel during a physical examination, suggests that the spleen is trapping platelets and that thrombocytopenia results from a disorder that is causing the spleen to enlarge.
The platelet count may be measured with an automated counter to determine the severity of thrombocytopenia, and a sample of blood may be examined under a microscope to provide clues to its cause. A sample of bone marrow removed and examined under a microscope ( bone marrow biopsy and aspiration Bone Marrow Examination Red blood cells, most white blood cells, and platelets are produced in the bone marrow, the soft fatty tissue inside bone cavities. Sometimes a sample of bone marrow must be examined to determine... read more ) may occasionally be needed to provide information about platelet production.
Treatment of Thrombocytopenia
Treatment of cause of thrombocytopenia
Avoidance of injury to minimize risk of bleeding
Drugs that increase production or decrease destruction of platelets
Sometimes platelet transfusion
Treating the cause can often treat the thrombocytopenia. Thrombocytopenia caused by a drug usually is corrected by stopping the drug. Thrombocytopenia caused by autoimmune destruction of platelets (as in immune thrombocytopenia Immune Thrombocytopenia (ITP) Immune thrombocytopenia (ITP) is a bleeding disorder caused by decrease in the number of platelets (thrombocytes) that occurs in a person who does not have another disorder that affects platelets... read more ) is treated with prednisone (a drug that suppresses the immune system to lessen platelet destruction), drugs that stimulate the bone marrow to increase production of platelets, and sometimes removal of the spleen (splenectomy).
People with a low platelet count and abnormal bleeding usually should not take drugs that impair platelet function (such as aspirin or nonsteroidal anti-inflammatory drugs).
People who have a very low platelet count are often treated in a hospital. When bleeding is severe, platelets may be transfused Overview of Blood Transfusion A blood transfusion is the transfer of blood or a blood component from one healthy person (a donor) to a sick person (a recipient). Transfusions are given to increase the blood's ability to... read more , although sometimes the transfused platelets also are destroyed by the underlying disorder.
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