ADAMTS13

The ADAMTS13 gene provides instructions for making an enzyme that is involved in blood clotting. After an injury, clots normally protect the body by sealing off damaged blood vessels and preventing further blood loss.

The ADAMTS13 enzyme processes a large protein called von Willebrand factor, which also plays a role in clot formation. The unprocessed form of von Willebrand factor interacts easily with cell fragments called platelets, which circulate in the bloodstream and are essential for blood clotting. The factor helps platelets stick together and adhere to the walls of blood vessels, forming temporary clots. The ADAMTS13 enzyme cuts von Willebrand factor into smaller pieces. By processing von Willebrand factor in this way, the enzyme prevents it from triggering the formation of unnecessary blood clots.

thrombotic thrombocytopenic purpura - caused by mutations in the ADAMTS13 gene

More than 70 mutations in the ADAMTS13 gene have been reported in people with the familial form of thrombotic thrombocytopenic purpura. Most of these mutations change single protein building blocks (amino acids) in the ADAMTS13 enzyme. Other mutations lead to the production of an abnormally small version of the enzyme that cannot function properly.

Mutations in the ADAMTS13 gene severely reduce the activity of the ADAMTS13 enzyme. As a result, von Willebrand factor is not processed normally in the bloodstream. If the factor is not cut into smaller fragments by the ADAMTS13 enzyme, it promotes the formation of abnormal clots throughout the body. The large, uncut version of von Willebrand factor induces platelets to stick together and adhere to the walls of blood vessels, even in the absence of injury. Additional factors such as pregnancy, diarrhea, surgery, and infection likely play a role in triggering abnormal clotting. Blood clots can block blood flow through small vessels, causing damage to the brain, kidneys, heart, and other organs. Abnormal clotting also causes other complications associated with thrombotic thrombocytopenic purpura.