Author reply to: Comment on: 'Eczematous drug eruption in patients with psoriasis under anti-interleukin-17A: does interleukin-22 play a key role?'

Background Eczematous drug eruption (EDE) is a spongiotic skin reaction in response to systemic medications. To date, EDE has been described in patients treated with anti-interleukin (IL)-17A monoclonal antibodies with a prevalence of 2.2%-12.1%. Aim To describe the clinical and histological features and the skin cytokine milieu in patients with EDE induced by anti-IL-17A biologics. Methods This was a prospective study, enrolling patients with psoriasis who developed EDE during treatment with two anti-IL-17 biologics, ixekizumab and secukinumab, from June 2019 to April 2021. Skin biopsies were taken from all patients: a 5-mm lesional biopsy (LB) and a 3-mm nonlesional biopsy (NLB). The LB sample was split into two parts, one for histological examination and the other for cytokine profile evaluation. Results During the study period, treatment with an anti-IL-17A drug was given to 289 patients of whom 8 (2.8%) developed EDE during the treatment. Histopathological evaluation suggested a diagnosis of spongiotic dermatitis in all eight patients. Cytokine gene expression showed a predominance of T helper (Th)2/Th22 cytokines in EDE lesions with a large increase in IL-4, IL-22 and S100A7 levels in both LB and NLB samples compared with healthy skin. IL-4, IL-22 and S100A7 were significantly higher in LB compared with NLB samples. IL-26 levels were also significantly increased in both LB and NLB compared with healthy skin, whereas low levels of IL-23A were found in both LB and NLB. Conclusion Eczematous drug eruption skin lesions have mainly Th2/Th22 features, with IL-22 playing a major role in their pathogenesis. EDE seems to be the result of an imbalance towards a Th2/Th22 response, secondary to the blockade of IL-17A activity.