Information about TTP-HUS for Patients, Their Families and Friends from:
The Oklahoma Blood Institute and the University of Oklahoma
It is hard to have an illness that neither you nor your family have ever heard of before. This information is written with the help of our patients, to help you understand what your doctor has told you.
TTP-HUS describes an illness for which the full name is too long to remember:
T is for Thrombotic, a term describing blood clots, which are called thrombi. In TTP-HUS, thrombi caused by clumps of platelets block small blood vessels. That can cause damage to organs such as the kidneys, heart, and brain.
T is for Thrombocytopenic, a term describing low platelet counts. Platelets are blood cells that are needed to stop bleeding. In TTP-HUS, they are used up in the abnormal clots that occur throughout the body.
P is for Purpura, a term describing the bruises and the small purple bleeding spots that are caused by too few platelets.
H is for Hemolytic, a term describing the anemia. Anemia means too few red blood cells. The anemia is caused by red blood cell damage, as blood forces its way through the thrombi (clots) that partially block the small blood vessels.
U is for Uremic, a term describing kidney failure.
S is simply for Syndrome, a term describing symptoms that occur together. Doctors use the word “syndrome” when there are no specific and defining diagnostic tests (such as a culture for strep throat or a biopsy for breast cancer).
The picture below is a microscopic view of blood cells from a patient with TTP. Notice that there are no platelets. There should be 10 to 20 platelets in this picture, just like in the picture of normal blood cells. Notice the broken shapes of the red blood cells. Compare these cells to the normal red blood cells. This is the result of blood trying to flow through partially obstructed blood vessels. This picture is an important part of the diagnosis of TTP-HUS.
WHAT IS TTP-HUS?
TTP-HUS was first recognized in 1924; in 1966 five key signs and symptoms were established: (1) thrombocytopenia, (2) hemolytic anemia, (3) kidney failure, (4) neurologic abnormalities (such as trouble with thinking or seeing, or actual stroke), and (5) fever. When these 5 problems occurred together, without an apparent cause, the “syndrome” of TTP-HUS was diagnosed. In that era almost all patients with TTP-HUS died. In 1975, it was discovered that plasma exchange could cure most patients with TTP-HUS. (Plasma exchange treatment is described below.) This created urgency to make the diagnosis and to begin treatment. Now patients are diagnosed earlier in their disease. The diagnosis is often made only when a low blood platelet count and anemia is present, when there is no kidney failure, no neurologic abnormalities, and no fever.
There is no specific diagnostic test that defines TTP-HUS. Therefore we begin plasma exchange treatment as soon as we have strong suspicion. This means we begin treatment on some patients who may not have TTP-HUS. In some patients, another diagnosis, such as a serious infection, is diagnosed and then we stop plasma exchange treatments. However we continue to carefully follow all patients whom we have treated with plasma exchange for TTP-HUS, including patients in whom another diagnosis was made. We do this by calling all of our former patients twice a year. Long-term follow-up helps us to improve our diagnosis and treatment.
We think of most diseases as problems with specific parts of the body: for example, pneumonia involves the lungs; hepatitis involves the liver; glaucoma involves the eyes. Some illnesses, such as allergic reactions to a food or medicine, cause a rash on the skin, sometimes over all of our body. In this example, the skin represents a single involved organ. TTP-HUS is a disease that involves the cells (called “endothelial cells”) that cover the inside of all of our small blood vessels throughout the body. Like our skin, these cells are also similar to each other and represent a single organ. Their main function is to prevent circulating blood cells from sticking to the vessel wall. The vessel wall lining is like Teflon – it prevents blood clotting.
These cells that form the inside lining of the vessel wall are the “organ” that is abnormal in TTP-HUS. They can be injured by the different causes of TTP-HUS listed below. When these cells are injured, the smooth flow of blood cells is disrupted. Blood platelets are consumed at the many points of injury, because the function of blood platelets is to seal any leaks that occur in blood vessels and prevent bleeding. When these cells are damaged throughout the body, platelets stick to the damaged areas and the platelet count may decrease to very low levels. The platelets can also stick to each other and block blood flow. This is the critical problem that occurs in TTP-HUS; these platelet clumps are the blood clots or thrombi described by the first “T” in TTP-HUS. Since the blood vessels and their lining cells are similar in all the organs of our body, all parts of our body can be affected in TTP-HUS.
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