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. These blood clots can cause serious problems if they block blood vessels and limit blood flow to the brain, kidneys, or heart.

Blood clots form when blood cells 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 and stop bleeding.

In TTP, when blood clots form, there are fewer platelets in the blood. This can cause bleeding into the skin (purpura), prolonged bleeding from cuts, and internal bleeding. It also causes 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 there’s a lower than normal number of platelets in the blood. Purpura (PURR-purr-ah) are purple bruises caused by bleeding into the skin.

Purpura

The photograph show purpura (bleeding) in the skin. Bleeding under the skin causes the purple, brown, and red color of the purpura.

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

TTP has two main types: inherited and acquired (noninherited) TTP.

“Inherited” means the condition is passed from parents to children. 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 occurs mostly in adults, but it sometimes affects children.

In acquired TTP, the ADAMTS13 gene isn’t changed. Instead, the body makes proteins called antibodies that block the ADAMTS13 enzyme’s activity.

What triggers inherited and acquired TTP isn’t known, but some factors may play a role. These include:

• Diseases and conditions such as pregnancy, cancer, HIV, infection, and lupus
• Medical procedures such as surgery and bone marrow transplant
• Medicines such as chemotherapy, ticlopidine, clopidogrel, cyclosporine A, and hormone replacement therapy and estrogens

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. About 1,200 people develop acquired TTP each year in the United States.

TTP usually occurs suddenly and lasts for days and weeks, but it can continue for months. Most people recover fully from TTP when treated promptly. Relapses (or flareups) can occur in 30 to 60 percent of people with acquired TTP. Many people with 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 disease.

September 2007