Immune thrombocytopenia (ITP), also known as immune or idiopathic thrombocytopenic purpura, is a blood disorder in which the immune system destroys platelets. As a result, people with ITP develop low platelet counts. This can cause red or purple dots on the skin, called petechiae, and problems with easy bruising, nosebleeds, blood blisters in the mouth or internal bleeding.
Platelets are produced in the bone marrow, along with red blood cells and white blood cells. Once in the blood, platelets plug small holes in blood vessel walls, preventing or stopping bleeding. Generally, people have about 140,000 to 450,000 platelets per microliter of blood at any given time. In people with ITP, however, the immune system produces antibodies that bind to platelets. The antibody-coated platelets are then removed from the patient’s bloodstream by the spleen, an internal organ next to the stomach that is part of the lymphatic system. This causes the low platelet count.
Some cases of ITP are mild and do not cause a significantly low platelet count or bleeding. As the platelet count decreases further, the risk of bleeding increases. Platelet counts less than 10,000 raise the concern for spontaneous bleeding. However, each person experiences bleeding symptoms differently for a given platelet count level.
In the United States, an estimated 30,000 new cases of ITP are diagnosed each year. Approximately 70 percent of adults with ITP are women, and 70 percent of these women are under the age of 40 when diagnosed. ITP is more common in children than in adults, and boys and girls are equally affected.
The most common symptoms of ITP are petechiae (red or purple dots on the skin), bruising and bleeding. When ITP is severe and the platelet count is less than 10,000, patients will often notice petechiae and bruising with minimal contact.
Bleeding can occur anywhere but is most typical in the nose, mouth and gut. Women often notice excessive menstrual bleeding. Rarely, but most dangerously, people with ITP can develop bleeding in the brain, which can be life-threatening.
ITP is suspected when an otherwise healthy patient has symptoms of a low platelet count, or is found to have a low platelet count on a routine complete blood count (CBC) test.
There is no one specific test to prove a patient has ITP. Instead, ITP is diagnosed by excluding other causes of a low platelet count. This includes making sure that the person does not have:
For certain individuals, additional testing can be performed to rule out:
Treatment is considered for patients who have:
If treatment is necessary, the most common treatments include:
Reviewed by health care specialists at UCSF Medical Center.