This is the first part of our series about the condition based on our patient booklet “Fast Facts for Patients: Thrombotic Thrombocytopenic Purpura”. This article explains what TTP is.

First, the Facts …

  • Thrombotic thrombocytopenic purpura (TTP) is a life-threatening condition and needs urgent and immediate hospital attention, but can be reversed quickly with intensive treatment.
  • There are two types of TTP:
    • immune TTP (iTTP), which occurs when your immune system mistakenly attacks your own cells
    • congenital TTP (cTTP), which is inherited.
  • Emergency treatments for iTTP are plasma exchange (the removal and replacement of part of your blood), steroids and a medication called caplacizumab.
  • Treatment with another medication called rituximab helps to reduce the risk of relapse.
  • Treatment for cTTP is usually different, involving replacement of an enzyme called ADAMTS13, such as by plasma infusion.

What Is TTP?

TTP is a rare blood disorder that affects around 6 people per 1 million of the UK population every year. It can affect any age group, but is most common in adults, particularly women. It is usually caused by the body’s immune system attacking an enzyme (a type of protein that helps with specific tasks in the body) in the blood called ADAMTS13, causing blood clots to form in vital organs.

Blood Cells

Blood flows around the body in blood vessels called arteries and veins. Blood is made up of three types of blood cell and liquid called plasma. Plasma contains several types of proteins that the body needs to function normally.


Red blood cells, platelets and white blood cells

Blood Clotting

Blood clotting is the process the body uses to control blood loss and promote healing. When you cut yourself, blood vessels are damaged, and platelets bind to blood-clotting proteins (known as coagulation factors) and clump together to help stop the bleeding. One of the most important of these is called von Willebrand factor, which is made as a very large protein in the body and needs to be cut up smaller to function normally. The ADAMTS13 enzyme in plasma normally does this.

What Happens in TTP?

People develop TTP when they don’t have the ADAMTS13 enzyme. Without ADAMTS13 to control it, von Willebrand factor can cause platelets to bind to each other, causing blood clots to form in small blood vessels that supply vital organs, usually the brain and heart. Red blood cells can be damaged as they flow past the blood clots and are broken down (by a process called hemolysis) leading to a lack of red blood cells and low levels of hemoglobin (anemia). Because the platelets are making clots, the number of platelets circulating in the blood becomes very low (thrombocytopenia).


Blood vessel in a person with ADAMTS13 and blood vessel in a person with TTP

In other words, if you have thrombocytopenia, you have low levels of platelets in your blood. If you have anemia, the number of healthy red blood cells and level of hemoglobin in your blood is too low for enough oxygen to be delivered around the body.


Please check out the other posts of our series here:


Information based on Fast Facts for Patients: Thrombotic Thrombocytopenic Purpura (Karger, 2022).

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