Thrombotic thrombocytopenic purpura


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Thrombotic thrombocytopenic purpura



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Thrombotic thrombocytopenic purpura


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USMLE® Step 1 questions

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Thrombotic thrombocytopenic purpura

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USMLE® Step 1 style questions USMLE

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A 9-year-old boy is brought to the emergency department by his parents due to prolonged bleeding following a tooth extraction earlier in the day. Past medical history is noncontributory. Temperature is 37.5°C (99.5°F), pulse is 88/min, respirations are 14/min, and blood pressure is 112/62 mmHg. Physical exam shows gingival bleeding and petechiae. Laboratory testing is obtained, and the results are shown below.  
Laboratory value  Result
 Hemoglobin  12 g/dL 
 Hematocrit  40% 
 Platelet count  95,000/mm3  
 Leukocyte count  9,000/mm3  
Coagulation studies  
 Prothrombin time (PT)  12 seconds 
 Activated partial thromboplastin time (aPTT)  29 seconds 
 Bleeding time*  15 minutes 
*Reference Range: 2-7 minutes  

Which of the following conditions is the patient at greatest risk of developing?   

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Thrombotic thrombocytopenic purpura (TTP) p. 424, 434


Content Reviewers

Kelly Johnson, MS


Jerry Ferro

Alaina Mueller

Megan Gullotto, MSMI

Thrombotic Thrombocytopenic Purpura, often referred to as TTP, is a rare, serious blood disease that results in many small blood clots forming throughout the body.

Typically, blood clot formation starts the tissue injury. Right away, some cells begin to release a protein called von Willebrand factor. This von Willebrand factor sticks to exposed fibers in the torn tissue and becomes like glue, allowing platelets to stick to the site.

As the platelets pile on top of one another, they link together into a mesh, which we call a clot. In TTP, there is often a severe deficiency of the enzyme ADAMTS13 which breaks down von Willebrand factor when it’s no longer needed.

Without this von Willebrand factor regulation by ADAMTS13, small blood clots can form more frequently throughout the body.

The small blood clots formed in a person with TTP can block normal blood flow through arteries and veins, leading to clinical findings that include decreased platelets, increased red blood cell destruction, and neurological issues such as headaches, mental changes, confusion, speech abnormalities, partial paralysis, seizures, or coma.

TTP can cause a wide range of other symptoms. Due to the low number of platelets, small areas of abnormal bleeding in the skin may occur which can be seen as a rash-like appearance or a purplish discoloration.

Other symptoms may affect the entire body including fever, weakness, fatigue, and extreme paleness. There can also be episodes of unusually heavy bleeding or abdominal pain accompanied by nausea and vomiting.

Acute kidney failure occurs in less than 10% of people with TTP and requires dialysis. Due to the lack of blood and urine filtration when the kidneys stop working properly, increased water, salt, and protein retention can occur causing an onset of symptoms within days including foot swelling, shortness of breath, headaches, fever, and an irregular heartbeat.


Thrombotic thrombocytopenic purpura (TTP) is a rare blood disorder that is characterized by the formation of small blood clots in the small blood vessels throughout the body. These clots can limit or block blood flow to vital organs, leading to tissue damage and organ dysfunction. TTP can also cause low levels of platelets (thrombocytopenia), which are important for blood clotting.

Although the exact cause of TTP is unknown, it's associated with a deficiency of ADAMTS13, an enzyme that breaks down the clotting protein called von Willebrand factor. Without sufficient levels of ADAMTS13 in the blood, large pieces of von Willebrand factor can move around the blood and increase platelet clotting and red blood cell destruction. TTP can be either congenital or acquired. Congenital TTP is caused by a genetic mutation that affects the production or function of ADAMTS13, while acquired TTP is often caused by the development of autoantibodies that target and destroy ADAMTS13.

TTP can cause a wide range of other symptoms such as easy bruising and bleeding, fever, weakness, fatigue, and extreme paleness. There can also be episodes of unusually heavy bleeding or abdominal pain accompanied by nausea and vomiting. Treatment typically involves plasmapheresis, steroids, and other drugs such as rituximab. Plasmapheresis is the process of exchanging plasma through a machine.


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