Which organism causes hemolytic uremic syndrome
**Core Concept:** Hemolytic uremic syndrome (HUS) is a rare but severe complication characterized by hemolytic anemia, thrombocytopenia, and acute kidney injury. It can be caused by different etiologies, including various types of infections, genetic disorders, and drug exposure.
**Why the Correct Answer is Right:** Shiga toxin-producing Escherichia coli (STEC) O157:H7 is the most common cause of HUS, particularly in children. This bacterium releases Shiga toxin, which binds to endothelial cells lining the blood vessels, leading to endothelial injury and activation. Activated platelets aggregate and form microthrombi, causing microangiopathic changes, including thrombocytopenia and microvascular hemolysis. The kidney is particularly vulnerable to these changes, leading to acute kidney injury and the development of HUS.
**Why Each Wrong Option is Incorrect:**
A. This option refers to Thrombotic thrombocytopenic purpura (TTP), which is a different entity from HUS. TTP is caused by a deficiency in ADAMTS13, which leads to uncontrolled platelet aggregation and microangiopathic hemolytic anemia.
B. This option refers to the "typical" HUS, which is usually caused by STEC but can also be secondary to other infections, such as adenovirus and rotavirus. It is not the only cause of HUS.
C. This option refers to a specific strain of E. coli, which is not the only cause of HUS. STEC O157:H7 is a common cause, but other bacteria, viruses, and genetic factors can also lead to HUS.
D. This option refers to a specific strain of E. coli, which is not the only cause of HUS. STEC O157:H7 is a common cause, but other bacteria, viruses, and genetic factors can also lead to HUS.
**Clinical Pearl:** Hemolytic uremic syndrome (HUS) is a clinical syndrome characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. It can be caused by various pathogens and genetic factors, making it essential for clinicians to consider this diagnosis in appropriate clinical scenarios. Prompt recognition and treatment can prevent severe morbidity and mortality.