What Are Platelet Function Disorders?
Various disorders can affect platelets, the components of the blood that help blood to clot and that maintain the integrity of the blood vessel wall. Normally, platelets are formed continuously from megakaryocytes (large bone marrow cells) in the bone marrow. From there, they are released into the blood, where they circulate and help with wound healing. For example, after a simple cut, platelets flowing by the damaged area collect, form a small clot that stanches blood flow, and release various substances that help the wound to heal.
Most platelet disorders are due to an insufficient number of platelets, a condition known as thrombocytopenia. This condition results either from inadequate production of platelets in the bone marrow or from their excessive destruction in the bloodstream.
Less often, the number of circulating platelets is normal, but they are defective and function improperly. In either case deficient platelet function can lead to excessive bleeding. The most common result is for blood to leak slowly from minute tears in the smallest blood vessels (capillaries), causing bright or dark red pinpoint-size hemorrhages, called petechiae, to appear on the skin.
Petechiae often occur on the lower legs (where gravity exerts increased pressure on blood vessel walls), on the inside of the cheeks (owing to pressure from chewing), or along areas constricted by tight clothing (such as brassiere straps). Petechiae in skin and mucous membranes are harmless, but they may be a harbinger of more serious internal bleeding, particularly bleeding from the gastrointestinal tract or from blood vessels in the brain (a potentially life-threatening complication known as intracranial hemorrhage).
There are a wide variety of causes of platelet disorders, and they can occur at any age. Some (e.g., chronic immune thrombocytopenic purpura) are hereditary disorders that may become obvious as early as infancy; for example, there may be excessive bleeding following circumcision. In older people, platelet disorders may manifest after a dental extraction or surgical procedure.
Outcome varies widely, depending on the cause and severity of the disorder. Some forms are mild and lifelong, with only minor bruising or limited periods of excessive bleeding; others arise suddenly and may be fatal. In general, older patients seem to be at higher risk of serious complications, such as intracranial hemorrhage.
What Causes Platelet Function Disorders?
- In many cases, platelet disorders are believed to be due to an autoimmune disorder (an attack, for unknown reasons, by the body’s immune system against its own healthy cells). In this case, platelets are destroyed prematurely as they circulate in the blood. A common unexplained autoimmune disorder is called idiopathic thrombocytopenic purpura (ITP), and platelets are rapidly destroyed in systemic lupus erythematosus, also an autoimmune disorder.
- Certain types of leukemia or bone marrow invasion by cancer can give rise to decreased platelet number and function.
- A number of infections, including rubella, mononucleosis, bacterial blood infections, malaria, hepatitis, tuberculosis (TB), and human immunodeficiency virus (HIV), can cause platelet disorders.
- A wide variety of drugs is capable of causing platelet disorders in a small percentage of people. Some of these drugs are very commonly used, including aspirin, ibuprofen, and antibiotics such as penicillin. Others include quinidine and quinine (used to treat malaria) and illicit intravenous drugs.
- In aplastic anemia, a rare but very serious condition, production of platelets (and other blood cells) in the bone marrow is severely suppressed. It can be induced by radiation or chemotherapy drugs (for cancer), gold compounds (used to treat arthritis), the antibiotic chloramphenicol, or exposure to organic solvent fumes, including benzene and glue. It also sometimes occurs in those with acute hepatitis, but in many cases the cause cannot be determined.
- Chronic alcoholism or deficiencies of certain B vitamins can cause platelet disorders.
- Massive blood transfusions can cause a temporary platelet deficiency, exacerbated at times by an immune reaction to the donor’s blood that leads to platelet destruction.
- Various genetic defects can cause inherited platelet disorders.
- Disseminated intravascular coagulation (DIC) involves impaired platelet function and direct decline in platelet number.
- Chemotherapy and radiation treatments for cancer or leukemia may destroy platelets.
Symptoms of Platelet Function Disorders
- Minor bleeding just under the surface of the skin or in the mouth—usually appears as multiple tiny, pinpoint-size specks (petechiae) on the lower legs or inner cheeks
- Bleeding of the gums or blood blisters in the mouth
- Bleeding from the gums when baby teeth fall out or after tooth extractions
- Easy bruising
- Prolonged or heavy menstrual periods.
- Prolonged bleeding after a minor cut or after dental or surgical procedures.
- Bleeding into the stomach or intestine
- Purpura--a purple discoloration of the skin after blood has leaked under it forming a bruise--often from no known trauma.
- Emergency symptoms: sudden onset of severe headache, nausea, vomiting, vision loss, or confusion (signs of a brain hemorrhage); black or tarry stools may indicate bleeding from the gastrointestinal tract.
There are no known ways to prevent platelet function disorders.
Platelet Function Disorders Diagnosis
- Patient history should include all drugs being taken and family history of bleeding disorders.
- Blood samples will be taken for a platelet count and to test platelet function and presence of platelet antibodies.
- A bone marrow aspiration and biopsy (removal of tissue through a needle inserted into the hip or thigh) may be necessary to determine whether adequate numbers of platelets are being manufactured.
How to Treat Platelet Function Disorders
- All patients should avoid aspirin and other drugs that can affect platelets until the condition clears. Those whose only symptoms are petechiae may need no additional treatment.
- For people with more serious bleeding disorders, transfusions of platelets are given (if no detectable antiplatelet antibodies are present) until the underlying defect is corrected and the body produces enough healthy platelets on its own. Those with chronic or inherited forms of the disease may require transfusions whenever bleeding problems arise or before surgical or dental procedures are performed.
- If a drug is found to be the cause, discontinuation of the drug usually resolves the problem quickly.
- Corticosteroid drugs may be prescribed to suppress the destruction of platelets by the immune system. The disorder often improves within several weeks and may disappear completely. Other immunosuppressive drugs may be tried as well.
- Those who continue to have platelet defects despite corticosteroids or other forms of therapy may benefit from surgical removal of the spleen (splenectomy). The spleen acts to produce helpful antibodies and to remove worn-out blood cells, including platelets. But in those with platelet disorders, it can become enlarged and overactive and thus stall recovery. Splenectomy—used especially in those with ITP—brings about long-term remissions in many patients without causing other long-term side effects.
In August 2015, the U.S. Food and Drug Administration (FDA) extended the approval of eltrombopag (Promacta)first approved for use in adults in 2008to include the treatment of low platelets in children over the age of 1 who have chronic immune thrombocytopenic purpura and have not responded to other medications or splenectomy. Common side effects include upper respiratory tract infections, abdominal pain, diarrhea, rash, and increased liver enzymes.
What to Call a Doctor
- See a doctor if you have symptoms of a bleeding disorder.
- If you have already been diagnosed with a platelet disorder, call a doctor if you notice increased bruising or new areas of petechiae or if you begin bleeding from the nose or gums.
- EMERGENCY Get to an emergency room immediately if symptoms of internal bleeding from the gastrointestinal tract (black, tarry stools) or brain (severe headache, nausea, vision loss) occur.
Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference
Simeon Margolis, M.D., Ph.D., Medical Editor
Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50
Updated by Remedy Health Media