Mogamulizumab is a cytotoxic anti-CC chemokine receptor 4 (CCR4) antibody against CCR4+ malignant T cells [1]. It also depletes regulatory T-cell (Treg) populations because CCR4 is expressed on Tregs [2-4]. A decrease in the number of Tregs induced by mogamulizumab can cause cutaneous adverse reactions (CAR), including Stevens-Johnson syndrome/toxic epidermal necrolysis [2, 4]. We report a case of a patient with mogamulizumab-induced CAR, who developed two further episodes of CAR which were probably [...]