P407 : A case of febuxostat-induced drug eruption in a patient with allopurinol hypersensitivity syndrome

A 73-year-old female presented with pruritic erythematous patches on whole body. She had been diagnosed as allopurinol hypersensitivity syndrome and treated with hypertension, diabetes and chronic kidney disease. The skin lesions started from 3 days ago after taking febuxostat due to hyperuricemia. On physical examination, there was no abdominal pain, arthralgia, hematuria, or Nikolsky’s sign. Histopathologic examination revealed pyknotic nucleus on Malpighi layer with vacuolar alteration and perivascular eosinophilic infiltration. She was finally diagnosed as drug eruption due to febuxostat. She stopped taking febuxostat immediately and started to take systemic steroid and antihistamines. Her skin lesions were resolved. Febuxostat is a new xanthine oxidase inhibitor, metabolized by liver. It can be used as urate-lowering agent in renal impairment and may show equivalent or greater hypouricemic activity compared to allopurinol, making it potential alternative to allopurinol. Furthermore, its chemical structure is completely different from allopurinol, thus theoretical probability to develop cross-reactivity with allopurinol is low. However, further researching cross-reactivity between allopurinol and febuxostat into sub-molecular level is needed. Herein, we report a rare case of febuxostat-induced drug eruption in a patient with allopurinol hypersensitivity syndrome emphasizing need for careful administration of urate-lowering agents.