Blood Platelet structure and functions in hemostasis

What Are Platelet Disorders?

Platelet Disorders

Platelet disorders are conditions that occur when the platelet count in your blood is too high or too low or your platelets do not work properly. Platelets are tiny blood cells that are made in the bone marrow from larger cells. When you are injured, platelets form a plug, called a blood clot, to seal your wound. Blood clots help stop or slow down bleeding.

There are many types of platelet disorders.

  • A higher-than-normal platelet count is called thrombocytosis or thrombocythemia. Having too many platelets can cause blood clots to form in your blood vessels. This can block blood flow through your body.
  • A lower-than-normal platelet count is called thrombocytopenia. Some types of thrombocytopenia are immune thrombocytopenia and thrombotic thrombocytopenic purpura. When you have a low platelet count, your blood does not clot normally. You may have trouble stopping bleeding.

Symptoms of platelet disorders include blood clots, bleeding, and bruising. You may not have any symptoms if your platelet count is not very high or very low. Your healthcare provider will diagnose your platelet disorder based on your medical history, a physical exam, and blood tests. Genes, lifestyle habits, and certain medical conditions or medicines can cause platelet disorders.

Your treatment for platelet disorders may include medicines and procedures to raise or lower your platelet count. If your condition is not serious, you may not need any treatment. Platelet disorders can cause serious bleeding, a stroke, and pregnancy complications. Your provider can help you manage your platelet disorder to lower your risk of complications.    

How does blood clot?

When a blood vessel is injured, the damaged cells in the vessel wall send out chemical signals. These signals cause clots that slow or stop bleeding.

A blood clot forms through several steps.

  1. Your blood vessel narrows. First, chemical signals cause the injured vessels to narrow to prevent more blood from leaking out.
  2. Platelets come to the site of injury. When you have a severe injury that is bleeding, chemical signals travel through your blood to the spleen, where many platelets are stored. The signals tell your spleen to release the platelets into your blood. Back at the injury site, the vessel walls become sticky and capture the platelets as they float past.
  3. A platelet plug forms. The platelets change shape and become stickier. This allows them to attach to the vessel wall and clump together into a plug.
  4. The clot forms. The platelets and other proteins in the blood called clotting factors form a blood clot. The clot contracts to pull the two sides of the damaged vessel closer together, so it is easier to repair.
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If you have a high platelet count, blood clots may form often in your blood vessels. These clots can block blood flow through your body and prevent your organs from getting enough blood. If you have a low platelet count, your blood may not clot normally. You may have trouble stopping bleeding. This can make you lose a lot of blood even from a small injury.

Bleeding disorders and blood clotting disorders also can affect how blood clots form in your body.

Symptoms of a high platelet count

Symptoms of a high platelet count are mostly caused by a blood clot. Your symptoms may include:  

  • Chest pain and heart palpitations, difficulty breathing
  • Dizziness, changes in your vision, weakness, numbness, slurred speech, or transient ischemic attacks
  • Extreme tiredness
  • Headaches
  • Pain and swelling of leg(s)
  • Spleen or liver that is larger than normal

Bleeding can happen when you have a high platelet count but your platelets do not work normally. It can also happen when blood clots use up all your platelets. You may have nosebleeds, bleeding from your gums, and blood in your urine or stool. Blood in your stool may make your stool appear black.

Symptoms of a low platelet count

Symptoms of a low platelet count or platelets that do not work properly include:  

  • Bleeding from your gums, nosebleeds, or bleeding for a long time after a small injury
  • Blood in your stool, urine, or vomit, or black stool or vomit that looks like coffee grounds
  • Bruising easily
  • Extreme tiredness
  • Heavy menstrual periods
  • Petechiae, which are small, flat red spots under the skin caused by blood leaking from blood vessels
  • Purpura, which is bleeding in your skin that can cause red, purple, or brownish- yellow spots
  • Spleen or liver that is larger than normal
  • Weakness and confusion


To diagnose a platelet disorder, your provider will ask about your medical and family history and do a physical exam to look for signs of a platelet disorder. They may do the following:

  • Feel your abdomen to see whether your spleen or liver is larger than normal.
  • Look at your eyes, nose, mouth, and skin for small, flat red spots called petechiae.
  • Look at your skin for bruising or purpura, which are red, purple, or brownish yellow spots on your skin.
  • Look for signs of other medical conditions that can cause platelet disorders.

Blood tests

Your provider will order one or more blood tests to diagnose your platelet disorder.

Complete blood count (CBC)

This test shows your platelet count and other blood cells in your blood.

Diagnosing high or low platelet counts 
 Platelet count,platelets per microliter
Normal platelet count150,000 to 400,000
High platelet countMore than 450,000
Low platelet countMildModerateSeriousSevereLess than 150,000100,000 to 150,00050,000 to 100,000Less than 50,000Less than 20,000

Platelet disorders are grouped based on platelet count, which is the platelet count in a certain amount of blood.  

  • A normal platelet count is between 150,000 and 400,000 platelets per microliter of blood.
  • A high platelet count is more than 450,000 platelets per microliter of blood.
  • A low platelet count is less than 150,000 platelets per microliter of blood.
    • A low platelet count is mild if it is between 100,000 and 150,000 per microliter.
    • It is severe if it is less than 20,000 per microliter.

Peripheral blood smear

This test shows the number, size, and shape of your platelets and other blood cells. In a peripheral blood smear, a small amount of your blood is examined under a microscope. Results from this test can help your provider find the cause of your platelet disorder.

Other tests and procedures

Your provider may order other tests to find out which platelet disorder you have. These tests can also help find the cause of your condition.

  • Abdominal ultrasound are used to look for changes in your liver, spleen, and the lymph nodes in your abdomen.
  • ADAMTS13 testing checks the level of a protein called ADAMTS13 in your blood. Levels of this protein are very low in people who have thrombotic thrombocytopenic purpura.
  • Blood clotting tests check how well your blood is clotting.
  • Bone marrow tests can help your provider see whether your bone marrow is healthy and making new blood cells. They will look for a bone marrow disease that may be causing your platelet disorder.
  • Genetic testing checks for mutations, or changes, in genes that control how your body makes platelets or how well your platelets work.
Medicines to treat high platelet count
  • Anagrelide: This medicine can lower platelet counts in people who have a high risk of complications such as serious blood clots. This medicine may cause anemia and scarring of your bone marrow.
  • Aspirin: This medicine helps prevent blood clots. Aspirin can raise your risk of bleeding.
  • Hydroxyurea: This is used to reduce platelet counts. Possible side effects include making fewer blood cells, skin wounds, problems with your digestive system, and fever.
  • Interferon-a and pegylated interferon: These medicines help reduce platelet counts. Side effects include extreme tiredness, flu-like symptoms, and confusion.
Medicine to treat low platelet count
  • Anti-D immunoglobulin: This medicine is used to increase platelet counts in some people who have immune thrombocytopenia. Possible side effects include flu-like symptoms, low hemoglobin levels, and a breakdown of your red blood cells.
  • Corticosteroids: These medicines help increase platelet counts. Corticosteroids include prednisone, prednisolone, and dexamethasone. This may be the first treatment your provider recommends for a low platelet count. Possible side effects include diabetes, insomnia, high blood pressure, digestive problems, mood changes, and slow growth in children.  
  • Fondaparinux: This is used to treat heparin-induced thrombocytopenia (HIT). This medicine may cause bleeding, anemia, insomnia, dizzinesslow blood pressure, and confusion.
  • Immunosuppressors: These medicines stop your immune system from destroying your platelets. They are used to treat immune thrombocytopenia when corticosteroids do not work. Examples of this type of medicine include azathioprine, cyclophosphamide, cyclosporine, danazol, and dapsone. These medicines may increase your risk for infection. Other, less serious side effects can include loss of appetite, nausea, vomiting, increased hair growth, and hand trembling. These effects get better and may go away as the body adjusts to the medicine.
  • Intravenous immunoglobulin (IVIG): This is used to increase your platelet count and treat major bleeding in immune thrombocytopenia. IVIG is also used to treat HIT. Complications may include serious allergic reactions and damage to your kidneys or lungs.
  • Rituximab: This is an antibody treatment that may be used to treat immune thrombocytopenia or thrombotic thrombocytopenic purpura. This medicine may raise your risk of infections.  
  • Thrombopoetin receptor agonist (TPO-RA) such as romiplostim and eltrombopag: These increase platelets in immune thrombocytopenia. They are used most often after other treatments have not worked. Possible side effects include low platelets, damage to the liver, venous thromboembolism, cataracts, bruising, and nosebleeds.

You may need one or more of the following procedures to treat your platelet disorder.

  • Plasma exchange: This is used to treat thrombotic thrombocytopenic purpura. In this procedure, the liquid part of your blood (plasma) is replaced with donor plasmas using a machine that collects the cells in your blood.
  • Plasma infusion: This is used to treat thrombotic thrombocytopenic purpura that is caused by your body not making enough of a protein called ADAMTS13. A plasma infusion helps replace the missing protein.
  • Platelet transfusion: This procedure is used to quickly increase your platelet count when you are having serious bleeding. Possible complications include risk of infectious disease, allergic reaction, and difficulty with future transfusions. If you have HIT, a platelet transfusion can raise your risk of forming blood clots.  
  • Plateletpheresis: This is used to treat life-threatening clotting in people who have high platelet counts. This procedure removes platelets from your blood and returns the liquid part of your blood (plasma) to your bloodstream.
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  • Bone marrow transplant: This procedure can help treat life-threatening types of platelet disorders. It is used to treat conditions that occur when the stem cells in your bone marrow do not make enough platelets.
  • Surgery to remove your spleen (splenectomy): Your spleen is an organ in your upper left abdomen that stores platelets. Removing your spleen helps raise your platelet count. This helps treat a low platelet count. Possible complications include bleeding, infection, and blood clots.



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