American Board of Internal Medicine (ABIM) Certification Practice Exam

How does rasburicase help patients with tumor lysis syndrome?

1. It increases uric acid production

2. It converts uric acid to allantoin

3. It decreases creatinine levels

4. It promotes potassium excretion

The correct answer is: It converts uric acid to allantoin

Rasburicase is a recombinant urate oxidase enzyme that plays a crucial role in the management of tumor lysis syndrome (TLS), particularly in patients at high risk of developing severe hyperuricemia. Tumor lysis syndrome occurs when cancer cells break down rapidly, leading to the release of large amounts of uric acid into the bloodstream. This sudden increase in uric acid can result in hyperuricemia and subsequent complications such as acute kidney injury. The correct mechanism by which rasburicase exerts its therapeutic effect is by converting uric acid into allantoin, a product that is much more soluble and less toxic than uric acid. Allantoin can be easily excreted by the kidneys, thereby reducing the concentration of uric acid in the plasma and minimizing the risk of uric acid nephropathy. This conversion is critical in preventing or treating hyperuricemia associated with TLS. In contrast, options that suggest increasing uric acid production or focusing on creatinine levels or potassium excretion do not pertain to the action of rasburicase. Instead, its primary function is to mitigate the accumulation of uric acid by facilitating its conversion to a less harmful and more easily eliminated compound. Understanding this mechanism