Idiopathic Thrombocytopenic Purpura

Alternate Names : Autoimmune Thrombocytopenia, ITP

Idiopathic thrombocytopenic purpura, which is also called ITP, is an autoimmune disorder that causes very low platelet counts. An autoimmune disorder is one in which a person produces antibodies against his or her own tissues.

What is going on in the body?

Platelets, which are made by the bone marrow, are essential for blood clotting. In ITP, the body produces antibodies that attack the platelets and destroy them. Normally the body makes antibodies to fight infections. In ITP, the body for some reason makes antibodies against its own tissues, called autoantibodies. These autoantibodies act to destroy platelets. The result is a low platelet count, known as thrombocytopenia.

The cause of ITP is unknown. But certain viral infections seem to cause some cases of ITP. This in turn creates antibodies that attack the platelets, which are then removed from the bloodstream. Normal platelet counts are between 150,000 and 450,000. People with ITP may have very low platelet counts, often lower than 20,000 to 50,000.

What are the causes and risks of the disease?

Viral infection is believed to be one of the things that causes the body to make antibodies against platelets. A recent immunization using a live virus is also associated with an increased risk of ITP. ITP is twice as common in females as in males. The disease is most common in adults who are 20 to 50 years of age and in children who are 2 to 9 years of age. ITP is more likely to cause bleeding in older individuals or people who have had bleeding problems in the past.

New research findings suggest that autoimmune disorders may be triggered by a transfer of cells between the fetus and the mother during pregnancy. The study involved women with scleroderma, an autoimmune disorder involving the skin. These women have more fetal cells in their blood decades after a pregnancy than women who don't have scleroderma. While further research is needed to substantiate these findings, the study does offer an explanation for the much higher incidence of autoimmune disorders in women than in men.