Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder. In TTP, blood clots form in small blood vessels throughout the body.
                
The clots can limit or block the flow of oxygen-rich blood to the body's organs, such as the brain, kidneys, and heart. As a result, serious health problems can develop.
                
The increased clotting that occurs in TTP also uses up platelets (PLATE-lets) in the blood. Platelets are blood cell fragments that help form blood clots. These cell fragments stick together to seal small cuts and breaks on blood vessel walls and stop bleeding.
                
With fewer platelets available in the blood, bleeding problems can occur. People who have TTP may bleed inside their bodies, underneath the skin, or from the surface of the skin. When cut or injured, they also may bleed longer than normal.
                
"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.
                
Bleeding under the skin also can cause 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
                

                
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 the body has a lower than normal number of 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. "Inherited" means the condition is passed from parents to children through 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 changed.
                
Acquired TTP is the more common type of the disorder. "Acquired" means you aren't born with the disorder, but you develop it. This type of TTP mostly occurs in adults, but it can affect children.
                
In acquired TTP, the ADAMTS13 gene isn't faulty. Instead, the body makes antibodies (proteins) that block the activity of the ADAMTS13 enzyme.
                
It's not clear what triggers inherited and acquired TTP, but some factors may play a role. These factors may include:
                
Some diseases and conditions, such as pregnancy, cancer, HIV, lupus, and infections
                
Some medical procedures, such as surgery and blood and marrow stem cell transplant
                
Some medicines, such as chemotherapy, ticlopidine, clopidogrel, cyclosporine A, and hormone therapy and estrogens
                
Quinine, which is a substance often found in tonic water and nutritional health products
                
If you have TTP, you may sometimes hear it referred to as TTPHUS. HUS, or hemolytic-uremic syndrome, is a disorder that resembles TTP, but is more common in children. Kidney problems also tend to be worse in HUS. Although some researchers think TTP and HUS are two forms of a single syndrome, recent evidence suggests that each has different causes.
                
Outlook
                
TTP is a rare disorder. It can be fatal or cause lasting damage, such as brain damage or a 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-feh-RE-sis). These treatments have greatly improved the outlook of the disorder.