Skin Related Paradoxical Adverse Events (Mainly Psoriasis) During Il-17 Blockage: A Systematic Review

Background: Paradoxical Adverse Events (PAEs) during biological therapy are characterized by the onset of a new inflammatory disease or by the exacerbation of the preexisting condition (with a different morphology or localization) while treating the patient with a class-agent proven efficacious for both conditions. They can be divided in two subgroups: “true PAE” characterized by the previously proven efficacy of the biological agent for the PAE and “borderline PAE” defined by the development of an inflammatory condition where the biological agent has not a proven efficacy. Methods: systematic search of English databases in order to identify true and borderline-skin PAE under anti IL-17 therapy. Results: We retrieved 58 patients affected by skin-PAE during anti-IL-17 therapy, 40 cases classified as True-PAE and 18 as Borderline-PAE., with a mean age of onset of 51 years. Secukinumab was the most frequent agent associated to skin-PAE and mean onset of the skin-PAE was 18 weeks. Conclusion: True-skin-PAE occur during anti Il-17 therapy, the underlaying immunological mechanism is not yet known, but pustular variants of psoriasis seem to be more prevalent; withdrawal of the anti-IL-17 therapy has been mainly performed and other therapies such as antiIL-23 biologics seem to control both the underlying disease and the true-skin-PAE. Further studies are needed in order to better understand the immunological mechanism involved.