ADAMTS13 defeciency is associated with which disease:
**Core Concept**
ADAMTS13 (A Disintegrin And Metalloproteinase with a ThromboSpondin type 1 motif, member 13) is a metalloprotease enzyme responsible for cleaving and regulating von Willebrand factor (VWF) in the blood. VWF is essential for platelet adhesion and aggregation at sites of vascular injury.
**Why the Correct Answer is Right**
ADAMTS13 deficiency leads to the accumulation of ultra-large VWF multimers, which are highly prothrombotic. This condition is characterized by a predisposition to develop thrombotic thrombocytopenic purpura (TTP), a rare blood disorder that involves the formation of blood clots in small blood vessels throughout the body. The deficiency of ADAMTS13 results in a failure to regulate VWF, leading to excessive platelet activation and aggregation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because TTP is a distinct clinical entity characterized by a specific set of laboratory findings, including ADAMTS13 deficiency, low platelet count, and microangiopathic hemolytic anemia.
* **Option B:** This option is incorrect because hemophilia A is caused by a deficiency in factor VIII, not ADAMTS13.
* **Option C:** This option is incorrect because atypical hemolytic uremic syndrome (aHUS) is caused by a deficiency in complement regulatory proteins, not ADAMTS13.
**Clinical Pearl / High-Yield Fact**
The diagnosis of TTP is often delayed due to its nonspecific clinical presentation. A key diagnostic clue is the presence of microangiopathic hemolytic anemia, which is characterized by schistocytes (fragmented red blood cells) on peripheral smear.
**Correct Answer: C. Thrombotic Thrombocytopenic Purpura (TTP)**