American Board of Internal Medicine (ABIM) Certification Practice Exam

What syndrome is associated with thrombotic microangiopathy due to Shiga toxin?

1. Hemolytic anemia

2. Acute kidney injury

3. Shiga toxin-associated hemolytic uremic syndrome

4. Hypercalcemia

The correct answer is: Shiga toxin-associated hemolytic uremic syndrome

The syndrome associated with thrombotic microangiopathy due to Shiga toxin is Shiga toxin-associated hemolytic uremic syndrome (STEC-HUS). This syndrome arises primarily from infections with certain strains of Escherichia coli (E. coli), especially E. coli O157:H7, which produce Shiga toxin. Upon entering the body, Shiga toxin can lead to the damage of endothelial cells, particularly in the kidneys and gastrointestinal tract. This endothelial damage results in a cascade of events characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury, a core triad of findings in HUS. The presence of thrombotic microangiopathy refers to the formation of small blood clots within the microcirculation, leading to tissue ischemia and organ dysfunction. In the context of Shiga toxin, this process is exacerbated by the toxin's effects on the vascular endothelium. Other choices describe conditions that may occur due to various underlying mechanisms, but they do not specifically refer to the Shiga toxin and its related hemolytic uremic syndrome. For instance, while hemolytic anemia and acute kidney injury may occur as part of the clinical picture of HUS,