Idiopathic thrombocytopenic purpura (ITP) is a bleeding condition in which the blood doesn't clot as it should. This is due to a low number of blood cell fragments called platelets (PLATE-lets).
Platelets also are called thrombocytes (THROM-bo-sites). They're made in your bone marrow along with other kinds of blood cells. Platelets stick together (clot) to seal small cuts or breaks on blood vessel walls and stop bleeding.
"Idiopathic" (id-ee-o-PATH-ick) means that the cause of the condition isn't known. "Thrombocytopenic" (throm-bo-cy-toe-PEE-nick) means there's a lower than normal number of platelets in the blood. "Purpura" (PURR-purr-ah) refers to purple bruises caused by bleeding under the skin.
People who have ITP often have purple bruises that appear on the skin or on the mucous membranes (for example, in the mouth). The bruises mean that bleeding has occurred in small blood vessels under the skin.
A person who has ITP also may have bleeding that results in tiny red or purple dots on the skin. These pinpoint-sized dots are called petechiae (peh-TEE-kee-ay). Petechiae may look like a rash.
Petechiae and Purpura
The photograph shows petechiae (red/purple dots) and purpura (bruises) in the skin. Bleeding under the skin causes the purple, brown, and red color of the petechiae and purpura.
People who have ITP also may have nosebleeds, bleeding from the gums when they have dental work done, or other bleeding that's hard to stop. Women who have ITP may have menstrual bleeding that's heavier than usual.
More extensive bleeding can cause hematomas (he-mah-TO-mas). A hematoma is a collection of clotted or partially clotted blood under the skin. It looks or feels like a lump.
Bleeding in the brain as a result of ITP is very rare, but can be life threatening if it occurs.
In most cases, an autoimmune response is believed to cause ITP. Normally your immune system helps your body fight off infections and diseases. But if you have ITP, your immune system attacks and destroys its own platelets. The reason why this happens isn’t known.
ITP can't be passed from one person to another.