Two days after induction chemotherapy for Burkitt lymphoma, a 22-year-old man develops oliguria. Investigations show potassium 6.8 mmol/L, phosphate 2.9 mmol/L, calcium 1.6 mmol/L, uric acid 890 µmol/L and creatinine 340 µmol/L. Along with hydration, which drug directly addresses the underlying enzyme deficiency exploited here?

• A Allopurinol
• B Febuxostat
• C Sodium polystyrene sulfonate
• D Rasburicase ✓

Explanation

This is tumour lysis syndrome: rapid cell lysis releases potassium, phosphate and nucleic acids that are metabolised to uric acid, precipitating obstructive uric acid nephropathy. Humans lack urate oxidase, so urate crystals form readily; rasburicase is recombinant urate oxidase that converts uric acid to soluble allantoin. Allopurinol and febuxostat only prevent new uric acid formation and do not clear the already elevated load.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.