Abbreviation for an enzyme responsible for the cleavage of von Willebrand Factor (vWF), important in the pathophysiology of Thrombotic Thrombocytopenic Purpura (TTP). The actual enzyme name (are you ready for this?) is “A Disintegrin And Metalloproteinase with a ThromboSpondin type 1 motif, member 13” (I warned you, didn’t I?).

vWF is a “multimer” composed of numerous protein fragments. When released from the endothelial cells lining blood vessels, vWF is composed of very large, or “ultra-large” multimers (“ULvWF multimers”). ADAMTS13 helps catalyze the cleavage of these huge things into smaller fragments. Platelets LOVE to bind to ULvWF multimers, and when they are present in abnormal quantities, abnormal small aggregates/clots (“microthrombi”) are formed. The lack or inhibition of ADAMTS13 leads to TTP, with damage to red blood cells, kidneys, and brain as a result of formation of numerous tiny blood clots (microthrombi). ADAMTS13 levels can be measured via laboratory testing, and such measurement is very important before starting plasma exchange in those suspected of having TTP or another thrombotic microangiopathy. However, the results are not generally available quickly, so in most cases, the ADAMTS13 results either support or refute the TTP diagnosis after treatment has already begun.

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