Thrombotic thrombocytopenic purpura (TTP) is a serious disorder that involves the formation of small blood clots throughout the body that block the flow of blood to vital organs such as the brain, heart, and kidneys.
Symptoms are related to where in the body blood clots form.
Diagnosis is based on the person's symptoms and blood test results.
(See also Overview of Platelet Disorders and Overview of Thrombocytopenia.)
Thrombotic means that blood clots form, thrombocytopenic means the platelet count is low, and purpura means that spots or bruises (usually red, purple, or black) appear on the skin. Thrombotic thrombocytopenic purpura (TTP) is a rare disorder in which many small blood clots (thrombi) form suddenly throughout the body. It is related to hemolytic-uremic syndrome (HUS), but it is more likely to occur in adults than HUS, which is more common in children.
The blood clots in TTP are not large clots that block large blood vessels, like in deep vein thrombosis. Instead, in TTP, there are many small clots that block small blood vessels throughout the body, particularly those in the brain, heart, and kidneys. The blood vessel blockage damages organs and can break apart red blood cells that pass through partially blocked vessels. The blood clots also use up an abnormally high number of platelets, which leads to a sharp decrease in the number of platelets in the bloodstream (termed thrombocytopenia).
Platelets are cell that are made in the bone marrow and circulate in the bloodstream and help blood clot. The blood usually contains about 140,000 to 440,000 platelets per microliter (140 to 440 × 109 per liter). When the platelet count falls below about 50,000 platelets per microliter of blood (50 × 109 per liter), bleeding can occur even after relatively minor injury. The most serious risk of bleeding, however, generally does not occur until the platelet count falls below 10,000 to 20,000 platelets per microliter of blood (10 to 20 ×109 per liter). At these very low levels, bleeding may occur without any recognized injury.
In most people, TTP is an autoimmune disorder in which the body's immune system creates antibodies that destroy an enzyme (ADAMTS13). When this enzyme is deficient, platelets start to clot inappropriately within blood vessels, the number of platelets in the blood (platelet count) decreases, and the organs in which the clots occur (such as the brain and kidneys) can be damaged.
Symptoms of Thrombotic Thrombocytopenic Purpura
In thrombotic thrombocytopenic purpura (TTP), symptoms develop suddenly.
Symptoms in TTP are quite distinct from symptoms of most other forms of thrombocytopenia.
In TTP, the small blood clots that develop (using up platelets) cause a wide range of symptoms and complications, some of which can be life threatening. Symptoms that result from clots in the brain may include headache, confusion, seizures, and coma. Symptoms that result from clots in the brain may come and go and may vary in severity. Symptoms that result from clots elsewhere in the body include abnormal heart rhythms, blood in the urine, and abdominal pain.
Diagnosis of Thrombotic Thrombocytopenic Purpura
Blood tests to measure platelet count and ADAMTS13 enzyme levels
Tests for autoantibodies against the ADAMTS13 enzyme
Tests to rule out other disorders that cause a low platelet count and bleeding
Doctors suspect thrombotic thrombocytopenic purpura (TTP) when they find a low platelet count in people who have been ill, who have taken certain medications, or who are pregnant.
Although there are no blood tests that specifically diagnose TTP, doctors do a number of blood tests that, together with people's symptoms, help make the diagnosis. These blood tests often include tests demonstrating that red blood cells are being destroyed, tests to see how well the kidneys are working, and tests to measure ADAMTS13 enzyme levels and the presence of antibodies against the enzyme.
Treatment of Thrombotic Thrombocytopenic Purpura
Corticosteroids and plasma exchange
With thrombotic thrombocytopenic purpura (TTP), people are often treated with corticosteroids and plasma exchange (plasma transfusions along with plasmapheresis). In plasmapheresis, blood is taken from the person and put in a machine that separates the blood cells from the liquid part of the blood (plasma). The plasma, which contains disease-causing antibodies, is discarded and the blood cells are returned to the person along with fresh plasma obtained from healthy donors.
caplacizumab may reduce the need for plasma exchange and speed recovery in TTP, it may increase the risk of bleeding.
