Definition of Thrombotic thrombocytopenic purpura:

Thrombotic thrombocytopenic purpura (TTP) is a blood disorder that causes blood clots to form in small blood vessels around the body, and leads to a low platelet count (thrombocytopenia).

See also: Hemolytic-uremic syndrome

Causes, incidence, and risk factors:

This disease may be caused by a lack of, or problems with, a certain enzyme (a type of protein) that is involved in blood clotting. These changes cause clotting to occur in an abnormal way.

• As the platelets clump together in these clots, fewer platelets are available in the blood in other parts of the body to help with clotting.
• This can lead to bleeding under the skin and purple-colored spots called purpura.

In some cases, the disorder is passed down through families (inherited) and patients are born with naturally low levels of this enzyme. This condition also may be related to:

• Bone marrow transplantation
• Cancer
• Chemotherapy
• Hematopoietic stem cell transplantation
• HIV infection
• Hormone replacement therapy and estrogens
• Medications (including ticlopidine, clopidogrel, guinine, and cyclosporine A)