In TTP, all of the following are seen except: March 2011
**Core Concept**
Thrombotic Thrombocytopenic Purpura (TTP) is a rare blood disorder characterized by the formation of blood clots in small blood vessels throughout the body, leading to microangiopathic hemolytic anemia, thrombocytopenia, renal failure, fever, and neurological symptoms. The pathophysiology of TTP involves the deficiency of ADAMTS13, a metalloprotease enzyme that cleaves and regulates von Willebrand factor (VWF).
**Why the Correct Answer is Right**
TTP is characterized by the following features: microangiopathic hemolytic anemia, thrombocytopenia, renal failure, fever, and neurological symptoms. The deficiency of ADAMTS13 leads to the accumulation of ultra-large VWF multimers, which are highly prothrombotic and contribute to the formation of blood clots in small blood vessels. The clinical presentation of TTP is a result of the consumption of platelets and the formation of microthrombi in various organs.
**Why Each Wrong Option is Incorrect**
**Option A:** Hemolytic uremic syndrome (HUS) is a condition that is similar to TTP but is typically associated with a non-bacterial infection. HUS is not a feature of TTP.
**Option B:** Microangiopathic hemolytic anemia is a hallmark of TTP, characterized by the fragmentation of red blood cells and the presence of schistocytes.
**Option C:** Thrombocytopenia is a common feature of TTP, resulting from the consumption of platelets in the formation of microthrombi.
**Option D:** Renal failure is a complication of TTP, resulting from the microvascular thrombi in the kidneys.
**Clinical Pearl / High-Yield Fact**
ADAMTS13 deficiency is a key feature of TTP, and its measurement is used as a diagnostic test for the condition. A low ADAMTS13 activity is strongly suggestive of TTP.
**Correct Answer:** A.