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Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) are thrombotic microangiopathies characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ dysfunction. TTP typically presents with neurological symptoms and fever, while HUS classically involves acute kidney injury and is often preceded by bloody diarrhea in children.
TTP results from deficiency of ADAMTS13 protease, leading to accumulation of ultra-large von Willebrand factor multimers that promote platelet aggregation and microvascular thrombosis. HUS is commonly caused by Shiga toxin-producing E. coli, which damages endothelial cells and activates the complement system, resulting in thrombotic microangiopathy primarily affecting the kidneys.
Diagnosis relies on identifying the classic pentad of microangiopathic hemolytic anemia, thrombocytopenia, neurological symptoms, fever, and renal dysfunction, though not all features may be present. Laboratory findings include schistocytes on blood smear, elevated LDH, decreased haptoglobin, and thrombocytopenia, with ADAMTS13 activity levels helping differentiate TTP from HUS. Urgent treatment with plasma exchange is crucial for TTP, while HUS management focuses on supportive care including dialysis when indicated.