Thrombotic Thrombocytopaenic Purpura

What is thrombotic thrombocytopenic purpura?

Thrombotic thrombocytopenic purpura is a rare disorder that causes blood clots (thrombi) to form in small blood vessels throughout the body. These clots can cause serious medical problems if they block vessels and restrict blood flow to organs such as the brain, kidneys, and heart. Resulting complications include neurological problems (such as personality changes, headaches, confusion, and slurred speech), fever, abnormal kidney function, abdominal pain, and heart problems.

In people with thrombotic thrombocytopenic purpura, clots in blood vessels are formed from clumps of platelets. Platelets are cell fragments that play a critical role in blood clotting. Because a large number of platelets are used to form clots in people with this disorder, fewer platelets are available to circulate in the bloodstream. A reduced level of circulating platelets is known as thrombocytopenia. Thrombocytopenia can lead to bleeding just under the surface of the skin, resulting in purplish spots called purpura.

This disorder also causes red blood cells to break down (undergo haemolysis) prematurely. As blood squeezes past clots within blood vessels, red blood cells can break apart. A condition called haemolytic anaemia occurs when red blood cells are destroyed faster than the body can replace them. This type of anaemia leads to paleness, yellowing of the eyes and skin (jaundice), fatigue, shortness of breath, and a rapid heart rate.

The two major forms of thrombotic thrombocytopenic purpura are an acquired (noninherited) form and a familial form. The acquired form usually appears in late childhood or adulthood. Affected individuals may have a single episode of signs and symptoms, or complications of the disorder may recur over time. The familial form of this disorder is much rarer and typically appears in infancy or early childhood. In people with the familial form, signs and symptoms often recur on a regular basis.

How common is thrombotic thrombocytopenic purpura?

The precise incidence of this condition is unknown, but researchers estimate that it affects at least 3.7 in 1 million adults in the United States. The disorder occurs more frequently in women than in men. The acquired form of thrombotic thrombocytopenic purpura is more common than the familial form.

What genes are related to thrombotic thrombocytopenic purpura?

Mutations in the ADAMTS13 gene cause thrombotic thrombocytopenic purpura.

The ADAMTS13 gene provides instructions for making an enzyme that is involved in the normal process of blood clotting. Both the familial form and the acquired form of thrombotic thrombocytopenic purpura result from a severe reduction in the activity of this enzyme. The familial form is caused by mutations in the ADAMTS13 gene that disrupt the enzyme's function. People with the acquired form do not have mutations in this gene; instead, their bodies produce antibodies that block the activity of the ADAMTS13 enzyme.

A lack of ADAMTS13 enzyme activity disrupts the usual balance between bleeding and clotting. Instead of forming blood clots in response to injury, clots form throughout the body as platelets bind together abnormally and stick to the walls of blood vessels. These clots can block small blood vessels, causing organ damage and other complications associated with thrombotic thrombocytopenic purpura.

How do people inherit thrombotic thrombocytopenic purpura?

The familial form of thrombotic thrombocytopenic purpura is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder are carriers of one copy of the altered gene but do not show signs and symptoms of the disorder.

What other names do people use for thrombotic thrombocytopenic purpura?

  • Familial Thrombotic Thrombocytopenia Purpura
  • Microangiopathic haemolytic anaemia
  • Moschkowitz Disease
  • Purpura, Thrombotic Thrombocytopenic
  • Thrombotic microangiopathy, familial
  • TTP

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