Platelet dysfunction may be due to a problem in the platelets themselves or to an external factor that alters the function of normal platelets.
(See also Overview of Platelet Disorders and Overview of Thrombocytopenia.)
Platelets are cells that are made in the bone marrow and circulate in the bloodstream and help blood clot. 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.
When platelets do not function properly, people are at risk of excessive bleeding due to injuries or even spontaneous bleeding. Platelet dysfunction may be
Inherited
Acquired
Inherited platelet disorders
Von Willebrand disease is the most common inherited platelet-related disorder. There are a number of other rare inherited disorders that affect platelets, including Glanzmann disease, Wiskott-Aldrich syndrome, Chédiak-Higashi syndrome, and Bernard-Soulier syndrome. Some of these syndromes include skin disorders, abnormalities in immune function, and reduced kidney function.
Acquired platelet disorders
Acquired platelet disorders are usually caused by certain
Medications
Diseases
The most common medications
Diseases that can affect platelet function include cirrhosis, multiple myeloma, kidney disease, and systemic lupus erythematosus (lupus).
Some people can develop platelet dysfunction after cardiopulmonary bypass during open-heart surgery.
Symptoms of Platelet Dysfunction
Symptoms depend on the cause and severity of platelet dysfunction.
People with inherited disorders of platelet dysfunction may have a lifelong history of easy bruising or excessive bleeding after minor injuries or minor surgery such as dental extractions. Boys may have had excessive bleeding after circumcision. Sometimes the first sign in women is that their menstrual periods are very heavy.
Other symptoms of platelet disorders include tiny dots (usually red or purple) called petechiae on the skin and bruising after minor injuries.
Ecchymoses are large purple bruises seen here on the leg.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Petechiae are small red, purple, or brown spots as seen here in the skin.
By permission of the publisher. From Deitcher S. In Atlas of Clinical Hematology. Edited by JO Armitage. Philadelphia, Current Medicine, 2004.
Petechiae are small red spots as seen here in the mouth.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Ecchymoses are large purple bruises seen here on the leg.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Petechiae are small red, purple, or brown spots as seen here in the skin.
By permission of the publisher. From Deitcher S. In Atlas of Clinical Hematology. Edited by JO Armitage. Philadelphia, Current Medicine, 2004.
Petechiae are small red spots as seen here in the mouth.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Diagnosis of Platelet Dysfunction
Blood tests to measure platelet count and clotting
Special tests to measure platelet function and bleeding
Doctors suspect a medication is causing platelet dysfunction if symptoms begin after a person starts taking that medication. Doctors suspect an inherited cause if symptoms begin early in life in people who do not have any other disorders or do not take any medications that cause platelet dysfunction.
Doctors first do a complete blood count (CBC) to measure the number of platelets and see whether the person's symptoms are caused by a low number of platelets (thrombocytopenia). If the number of platelets is normal, doctors suspect there may be platelet dysfunction. If the cause is not clear, doctors may need to do other blood tests to measure substances that are involved in clotting (prothrombin time [PT] and partial thromboplastin time [PTT]). These tests measure how long it takes blood to clot. In other tests, called platelet function tests, a sample of blood is collected and tested to see if platelets react normally to various platelet stimulators. Abnormal platelet function tests may indicate the nature of the inherited or acquired platelet dysfunction.
Treatment of Platelet Dysfunction
Stopping or avoiding medications that cause bleeding
Treating the underlying associated disease, for example, dialysis for a person with kidney failure
Sometimes medications that decrease bleeding or sometimes platelet transfusion
If platelet dysfunction is caused by a medication, stopping the medication usually is the only treatment needed. People with an inherited platelet disorder that causes excessive bleeding usually should not take medications that impair platelet function.
