Allopurinol inhibits xanthine oxidase. It is used for chronic gout as well as prevention of tumor-lysis associated urate nephropathy.
This one was a somewhat simple question since chemotherapy --> tumor lysis --> need xanthine oxidase inhibitor (eg, febuxostat).
BUT WHY IS NBME GRAMMAR SO CRAP? PUT YOUR COMMAS IN THE RIGHT PLACE!
Dx: Acute Monocytic Leukemia. Proliferation of monoblasts; lack MPO. CD14 + CD13+ MPO -. blasts characteristically infiltrate the gums.
A Xanthine Oxidase inhibitor is given to prevent adverse reactions of Tumor Lysis Syndrome which results from expulsion of cellular debris/material after the cell dies.