Clinical and histopathological characterization of eczematous eruptions occurring in course of anti IL-17 treatment: a case series and review of the literature.

: Real-life data often highlight the side effects of certain drugs not previously reported in randomized controlled trials (RCTs). To describe cutaneous inflammatory eruptions in psoriatic patients treated with an anti IL-17A agent (secukinumab or ixekizumab).: Retrospective analysis of a cohort of patients with chronic plaque psoriasis who started an anti IL-17A agent between September 2016-February 2019 and who developed cutaneous inflammatory eruptions during treatment. A systematic review of similar events reported in the literature was performed.: Data of 468 patients were reviewed and 27 cutaneous inflammatory eruptions of 27 (5.8%) patients were collected. The eruptions appeared after a mean of 16.9 ± 17.0 weeks of therapy showing a classical acute eczema in 11 patients (40.7%), an atopic dermatitis-like rash in 11 patients (40.7%) and a psoriasiform eruption in 5 patients (18.5%). Histopathology of 12/27 cases showed epidermal spongiosis in all these variants.: We described the clinic-pathologic features of some eczematous eruptions occurring in psoriatic patients, 3-4 months after treatment initiation with an anti IL-17A agent. Further investigations are needed to explain this phenomenon, that might be defined a paradoxical adverse event, based upon the role of IL17 in eczema pathogenesis.