What Is Thrombotic Thrombocytopenic Purpura?

Thrombotic thrombocytopenic purpura (TTP) is a rare blood condition. It causes blood clots to form in small blood vessels throughout the body. The blood clots can cause serious problems if they block the blood vessels and limit blood flow to the brain, kidneys, or heart.

Blood clots form when blood cell fragments called platelets (PLATE-lets) clump together. Platelets are made in your bone marrow along with other kinds of blood cells. They stick together to seal small cuts or breaks on blood vessel walls and stop bleeding.

In TTP, when blood clots form, the result is fewer platelets in the blood. This can cause bleeding into the skin, prolonged bleeding from cuts, and internal bleeding. It also can cause small blood clots to form suddenly throughout the body, including in the brain and kidneys.

"Thrombotic" (throm-BOT-ik) refers to the blood clots that form. "Thrombocytopenic" (throm-bo-cy-toe-PEE-nick) means the blood has a lower than normal number of platelets. "Purpura" (PURR-purr-ah) refers to purple bruises caused by bleeding under the skin.

If you have TTP, you 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.

Purpura and Petechiae

The photograph shows purpura (bruises) and petechiae (dots) in the skin. Bleeding under the skin causes the purple, brown, and red colors of the purpura and petechiae.

TTP also can cause red blood cells to break apart faster than the body can replace them. This leads to hemolytic anemia (HEE-moh-lit-ick uh-NEE-me-uh)—a rare form of anemia. Anemia is a condition in which a person's blood doesn't have enough red blood cells.

A lack of activity in the ADAMTS13 enzyme (a type of protein in the blood) causes TTP. The ADAMTS13 gene controls the enzyme, which is involved in blood clotting. The enzyme breaks up a large protein called von Willebrand factor that clumps together with platelets to form blood clots.

Types of Thrombotic Thrombocytopenic Purpura

The two main types of TTP are inherited and acquired (noninherited). "Inherited" means the condition is passed from parents to children through the genes. This type of TTP mainly affects newborns and children.

In inherited TTP, the ADAMTS13 gene is faulty and doesn't prompt the body to make a normal ADAMTS13 enzyme. As a result, enzyme activity is lacking or is changed.

Acquired TTP is the more common type. "Acquired" means you aren't born with the condition, but you develop it. This type of TTP mostly occurs in adults, but sometimes it affects children.

In acquired TTP, the ADAMTS13 gene isn't faulty. Instead, the body makes antibodies (proteins) that block the ADAMTS13 enzyme's activity.

What triggers TTP isn't known, but some factors may play a role. These factors may include:

• Some diseases and conditions, such as pregnancy, cancer, HIV, infections, and lupus
• Some medical procedures, such as surgery and blood and marrow stem cell transplant
• Some medicines, such as chemotherapy, ticlopidine, clopidogrel, cyclosporine A, and hormone replacement therapy and estrogens
• Quinine, which is a substance often found in tonic water and nutritional health products

Outlook

TTP is a rare condition. It can be fatal or cause lasting damage, such as brain damage or stroke, if it's not treated right away.

TTP usually occurs suddenly and lasts for days or weeks, but it can continue for months. Relapses (or flareups) can occur in up to 60 percent of people who have the acquired type of TTP. Many people who have inherited TTP have frequent flareups that need to be treated.

Treatments for TTP include infusions of fresh frozen plasma and plasma exchange (also called plasmapheresis (PLAZ-ma-fe-RE-sis)). These treatments have greatly improved the outlook of the condition.

Revised November 2009