Why does thrombocytopenia occur

ITP is a bleeding disorder in which the blood doesn't clot as it should. An autoimmune response is thought to cause most cases of ITP. Normally, your immune system helps your body fight off infections and diseases.

But if you have ITP, your immune system attacks and destroys its own platelets. Why this happens isn't known. ITP also may occur if the immune system attacks your bone marrow, which makes platelets.

A reaction to medicine can confuse your body and cause it to destroy its platelets. Quinine is a substance often found in tonic water and nutritional health products. Heparin is a medicine commonly used to prevent blood clots. But an immune reaction may trigger the medicine to cause blood clots and thrombocytopenia.

This condition is called heparin-induced thrombocytopenia HIT. HIT rarely occurs outside of a hospital. In HIT, the body's immune system attacks a substance formed by heparin and a protein on the surface of the platelets. This attack activates the platelets and they start to form blood clots.

Blood clots can form deep in the legs deep vein thrombosis , or they can break loose and travel to the lungs pulmonary embolism. A low platelet count can occur after blood poisoning from a widespread bacterial infection. A virus, such as mononucleosis or cytomegalovirus, also can cause a low platelet count. Platelets can be destroyed when they pass through man-made heart valves, blood vessel grafts, or machines and tubing used for blood transfusions or bypass surgery.

About 5 percent of pregnant women develop mild thrombocytopenia when they're close to delivery. The exact cause isn't known for sure. Some rare and serious conditions can cause a low platelet count. TTP is a rare blood condition. It causes blood clots to form in the body's small blood vessels, including vessels in the brains, kidneys, and heart. DIC is a rare complication of pregnancy, severe infections, or severe trauma. Tiny blood clots form suddenly throughout the body.

Usually, one-third of the body's platelets are held in the spleen. If the spleen is enlarged, it will hold on to too many platelets. This means that not enough platelets will circulate in the blood.

An enlarged spleen often is due to cancer or severe liver disease, such as cirrhosis sir-RO-sis. Cirrhosis is a disease in which the liver is scarred.

This prevents it from working well. An enlarged spleen also might be due to a bone marrow condition, such as myelofibrosis MI-eh-lo-fi-BRO-sis. With this condition, the bone marrow is scarred and isn't able to make blood cells.

People who are at highest risk for thrombocytopenia are those affected by one of the conditions or factors discussed in "What Causes Thrombocytopenia? Whether you can prevent thrombocytopenia depends on its specific cause. Usually the condition can't be prevented.

However, you can take steps to prevent health problems associated with thrombocytopenia. For example:. Mild to serious bleeding causes the main signs and symptoms of thrombocytopenia.

Signs and symptoms can appear suddenly or over time. Mild thrombocytopenia often has no signs or symptoms. Many times, it's found during a routine blood test. Check with your doctor if you have any signs of bleeding.

Severe thrombocytopenia can cause bleeding in almost any part of the body. Bleeding can lead to a medical emergency and should be treated right away. External bleeding usually is the first sign of a low platelet count.

Purpura are purple, brown, and red bruises. This bruising may happen easily and often. Petechiae are small red or purple dots on your skin. Purpura and petechiae in the skin. The photograph shows two types of bruising that are often seen with DIC. The larger red, brown, and purple dots are purpura and the smaller red and purple dots are petechiae.

Heavy bleeding into the intestines or the brain internal bleeding is serious and can be fatal. Signs and symptoms include:. Your doctor will diagnose thrombocytopenia based on your medical history, a physical exam, and test results.

A hematologist also may be involved in your care. This is a doctor who specializes in diagnosing and treating blood diseases and conditions. Your doctor will do a physical exam to look for signs and symptoms of bleeding, such as bruises or spots on the skin. He or she will check your abdomen for signs of an enlarged spleen or liver. You also will be checked for signs of infection, such as a fever. Your doctor may recommend one or more of the following tests to help diagnose a low platelet count.

For more information about blood tests, go to the Health Topics Blood Tests article. A complete blood count CBC measures the levels of red blood cells, white blood cells, and platelets in your blood. For this test, a small amount of blood is drawn from a blood vessel, usually in your arm.

If you have thrombocytopenia, the results of this test will show that your platelet count is low. A blood smear is used to check the appearance of your platelets under a microscope. Bone marrow tests check whether your bone marrow is healthy. Blood cells, including platelets, are made in your bone marrow. The two bone marrow tests are aspiration as-pih-RA-shun and biopsy. Bone marrow aspiration might be done to find out why your bone marrow isn't making enough blood cells.

For this test, your doctor removes a sample of fluid bone marrow through a needle. He or she examines the sample under a microscope to check for faulty cells. A bone marrow biopsy often is done right after an aspiration. For this test, your doctor removes a sample of bone marrow tissue through a needle. He or she examines the tissue to check the number and types of cells in the bone marrow.

If a bleeding problem is suspected, you may need other blood tests as well. For example, your doctor may recommend PT and PTT tests to see whether your blood is clotting properly. Your doctor also may suggest an ultrasound to check your spleen.

An ultrasound uses sound waves to create pictures of your spleen. This will allow your doctor to see whether your spleen is enlarged. Treatment for thrombocytopenia depends on its cause and severity. If the cause is a drug being taken for a different condition, the prescribing doctor might change the medication.

Symptoms of a low platelet count only occur at severely low levels. A slightly lower-than-normal count may not produce symptoms. If the count is low enough to cause spontaneous bleeding, an individual may notice small bleeds that create small, round, dark red spots on the skin called petechiae.

ITP can also cause the gums or nose to bleed without reason and the presence of blood in the urine or stools. Platelets form a crucial part of the composition of blood. They are responsible for repairing tissue damage and play a vital role in the blood-clotting system, which helps to stop bleeding and heal wounds. Blood clotting is also known as hemostasis.

Platelets are not invisible to the naked eye. The bone marrow produces them, and they travel in the blood for an average of 10 days before being destroyed. When a blood vessel wall is damaged, it exposes a substance that activates platelets.

Activated platelets trigger further events that bring in more platelets, and a blood clot starts to form. This serves to plug any leak. Activated platelets also release sticky proteins to help form the clot. A protein known as fibrin forms a mesh of threads that holds the plug together. A platelet count measures the concentration of platelets in the blood.

A technician would carry this test out in a laboratory. When the number of platelets is low, this concentration reduces. Women normally experience a platelet count that varies slightly during the menstrual cycle and can fall near the end of pregnancy. A doctor will ask some questions and perform a physical examination.

The questions might cover symptoms, family history, and medications. The examination will assess for skin rashes and bruising. A laboratory platelet count will confirm the diagnosis, showing the exact concentration of platelets in the blood. The doctor is likely to perform other blood tests at the same time. These may include :. Some people may need to give a sample of their bone marrow.

Drug-induced cytopenia may be the result of. 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. By permission of the publisher. From Deitcher S. In Atlas of Clinical Hematology. Edited by JO Armitage. Philadelphia, Current Medicine, Doctors suspect thrombocytopenia in people who have abnormal bruising and bleeding.

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, thrombotic thrombocytopenic purpura, or hemolytic-uremic syndrome.

An enlarged spleen, 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 Treating the cause can often treat the thrombocytopenia.