Platelets are made in the bone marrow along with other kinds of blood cells. They travel through the blood vessels and stick together (clot) to stop any bleeding that could happen if a blood vessel is damaged. Platelets also are called thrombocytes, because a clot also is called a thrombus.
OverviewWhen the blood has a low number of platelets, mild to serious bleeding can occur. This bleeding can happen inside the body (internal bleeding) or on the skin.
A normal platelet count is 150,000 to 450,000 platelets per microliter of blood. A count of less than 150,000 platelets per microliter is lower than normal. But the risk for serious bleeding doesn't occur until the count becomes very low – less than 10,000 or 20,000 platelets per microliter. Milder bleeding sometimes occurs when the count is less than 50,000 platelets per microliter.
Several factors can cause a low platelet count, such as:
The treatment for this condition also depends on its cause and severity. Mild thrombocytopenia most often doesn't need treatment. If the condition is causing serious bleeding, or if a person is at risk for serious bleeding, he or she may need medicines or blood or platelet transfusions. Rarely, the spleen may need to be removed.
OutlookThrombocytopenia can be fatal, especially if the bleeding is severe or occurs in the brain. However, the overall outlook is good, especially if the cause of the low platelet count is found and treated.
What causes thrombocytopenia?A number of factors can cause thrombocytopenia (low platelet count). The condition can be inherited (passed from parents to children), or it can develop at any age. Sometimes the cause isn't known.
The bone marrow doesn't make enough plateletsBone marrow is the sponge-like tissue inside the bones. It contains stem cells that develop into red blood cells, white blood cells, and platelets. When stem cells are damaged, they don't grow into healthy blood cells.
Several conditions or factors can damage stem cells.
Cancer, such as leukemia or lymphoma, can damage the bone marrow and destroy blood stem cells. Cancer treatments, such as radiation and chemotherapy, also destroy the stem cells.
Aplastic anemia is a rare, serious blood disorder in which the bone marrow stops making enough new blood cells. This lowers the number of platelets in the blood.
Exposure to toxic chemicals, such as pesticides, arsenic, and benzene, can slow the production of platelets.
Some medicines, such as diuretics and chloromycetin (chloramphenicol), can slow the production of platelets. Chloramphenicol (an antibiotic) is rarely used in the United States.
Common over-the-counter medicines, such as aspirin or ibuprofen, also can affect platelets.
Alcohol also slows the production of platelets. A temporary drop in platelets is common among heavy drinkers, especially if they're eating foods that are low in iron, vitamin B12, or folate.
Chickenpox, mumps, rubella, Epstein-Barr virus, or parvovirus can decrease the platelet count for a while. People who have AIDS often develop thrombocytopenia.
Some genetic conditions, such as Wiskott-Aldrich and May-Hegglin syndromes, can cause low numbers of platelets in the blood.
The body destroys its own plateletsA low platelet count can occur even if the bone marrow makes enough platelets. The body may destroy its own platelets due to autoimmune diseases, certain medicines, infections, surgery, pregnancy, and some conditions that cause too much blood clotting.
With autoimmune diseases, the body's immune system destroys its own platelets. One example of this type of disease is called idiopathic thrombocytopenic purpura, or ITP.
In most cases, the body's immune system is thought to cause 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 – for an unknown reason.
Other autoimmune diseases that destroy platelets include lupus and rheumatoid arthritis.
A reaction to some medicines can confuse your body and cause it to destroy its platelets. Any medicine can cause this reaction, but it happens most often with quinine, antibiotics that contain sulfa, and some medicines for seizures, such as Dilantin, vancomycin, and rifampin.
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, or a clot can break loose and travel to the lungs.
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.
Rare and serious conditions that cause blood clots
Some diseases can cause a low platelet count. Two examples are thrombotic thrombocytopenic purpura (TTP) and disseminated intravascular clotting (DIC).
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.
In both conditions, the blood clots use up many of the blood's platelets.
The spleen holds on to too many plateletsUsually, 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 is often due to severe liver disease – such as cirrhosis or cancer. Cirrhosis is a disease in which the liver is scarred. This prevents it from working properly.
An enlarged spleen also may be due to a bone marrow condition, such as myelofibrosis. With this condition, the bone marrow is scarred and isn't able to make blood cells.
Who is at risk for thrombocytopenia?People who are at highest risk for thrombocytopenia are those affected by one of the conditions or factors discussed in "What Causes Thrombocytopenia?" This includes people who have:
Signs and symptoms of thrombocytopeniaMild to serious bleeding causes the main signs and symptoms of thrombocytopenia. Bleeding can occur inside the body (internal bleeding) or on the skin. 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 a doctor if you have any signs of bleeding. Severe thrombocytopenia can cause bleeding in almost any part of the body. This can lead to a medical emergency and should be treated right away.
Bleeding on the skin is usually the first sign of a low platelet count. This may appear as:
Heavy bleeding into the intestines or the brain is serious and can be fatal. Signs and symptoms include:
DiagnosisYour 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 treats blood diseases.
Once thrombocytopenia is diagnosed, your doctor will begin looking for its cause.
Medical historyYour doctor may ask you about factors that can affect your platelets, such as:
Physical examYour 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.
Diagnostic testsYour doctor may order one or more of the following tests to help diagnose a low platelet count.
Complete blood count
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. For this test, a small amount of blood is drawn from a blood vessel, usually in your arm.
Bone marrow tests
Bone marrow tests check whether your bone marrow is healthy. Blood cells, including platelets, are made in bone marrow. The two bone marrow tests are aspiration and biopsy.
Bone marrow aspiration may be done to find out why your bone marrow isn't making enough blood cells. For this test, your doctor removes a small amount of fluid bone marrow through a needle. He or she examines the sample under a microscope to check for abnormal cells.
A bone marrow biopsy often is done right after an aspiration. For this test, your doctor removes a small amount of bone marrow tissue through a needle. Your doctor 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, tests called PT and PTT may be done to see whether your blood is clotting properly.
Your doctor may order 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.
TreatmentTreatment for thrombocytopenia depends on its cause and how severe the condition is. The primary goal of treatment is to prevent death and disability caused by bleeding.
If your condition is mild, you may not need treatment. Your doctor should reassure you that a fully normal platelet count isn't necessary to prevent bleeding, even with severe cuts or accidents.
Thrombocytopenia often improves when its underlying cause is treated. People who inherit the condition usually don't need treatment.
If a reaction to medicine is causing a low platelet count, your doctor may prescribe other medicine. Most people recover after the offending medicine has been stopped. For heparin-induced thrombocytopenia (HIT), stopping the heparin isn't enough. Often, you'll need another medicine to prevent blood clotting.
If your immune system is causing a low platelet count, your doctor may prescribe medicines to suppress the immune system. When the condition is severe, treatments may include:
PreventionWhether you can prevent thrombocytopenia depends on its specific cause. Most cases of the condition can't be prevented. However, you can take steps to prevent its complications.
Living with thrombocytopeniaIf you have thrombocytopenia, watch for any signs and symptoms of bleeding. Report these signs and symptoms to your doctor right away.
Symptoms can appear suddenly or over time. Severe thrombocytopenia can cause bleeding in almost any part of the body. This can lead to a medical emergency and should be treated right away.
You can take steps to avoid complications of thrombocytopenia. Watch what medicines you take, avoid injury, and contact your doctor if you have fever or other signs or symptoms of an infection.
MedicinesAvoid medicines that may affect your platelets and raise your risk for bleeding. Two examples of such medicines are aspirin and ibuprofen. These medicines may thin your blood too much. Be careful when using over-the-counter medicines, because many contain aspirin or ibuprofen.
Tell your doctor about all of the medicines you take, including over-the-counter medicines, vitamins, supplements, and herbal remedies.
InjuryAvoid injuries that can cause bruising and bleeding. Don't participate in contact sports such as boxing, football, or karate. These sports are likely to lead to injuries that can cause bleeding.
Other sports, such as skiing or horseback riding, also put you at risk for injuries that can cause bleeding. Ask your doctor about physical activities that are safe for you.
Take safety precautions, such as using seatbelts and wearing gloves when working with knives and other tools.
If your child has thrombocytopenia, try to protect him or her from injuries, especially head injuries that can cause bleeding in the brain. Ask your child's doctor whether you need to restrict your child's activities.
InfectionIf you've had your spleen removed, you may be more likely to become ill from certain types of infection. Watch for fever or other signs and symptoms of infection and report them to your doctor promptly. People who have had their spleens removed may need vaccinations to prevent these infections.
Related category• HEALTH AND DISEASE
Source: U.S. National Heart, Lung and Blood Institute
Home • About • Copyright © The Worlds of David Darling • Encyclopedia of Alternative Energy • Contact