LAUSR

Dear Editor, We read with interest the recent article by Singh and Cleveland on the hypersensitivity risk of allopurinol (ALP) and febuxostat (FBX) compared with colchicine.1 A common challenge when using ALP, linked to hypersensitivity reactions, is the potential development of cutaneous adverse reactions (CARs). Most are often mild, non-specific rashes; however, severe CARs, including Stevens-Johnson syndrome (SJS), may occur, but with a low incidence (0.69 cases per 1000 person-years) in non-Asian populations.2 In the EuroSCARs study, ALP was the reason for 5% of all severe CARs.3 So, FBX is often chosen as urate-lowering agent on the background of an ALP-related CAR. However, these patients were not eligible for the pivotal trials of FBX4 and were excluded from the recent analysis by Singh and Cleveland.1 Therefore, the accurate rate of FBX-related CARs in patients who previously suffered from ALP, and the mechanisms behind, remain undetermined to date. We have …