Supplementary Material for: Paradoxical Hidradenitis Suppurativa in Patients Receiving TNF-α Inhibitors: Case Series, Systematic Review, and Case Meta-Analysis

Background/Aims: TNF-α inhibitors represent the most advanced approved therapeutic option for moderate and severe forms of hidradenitis suppurativa (HS). However, in recent years, cases of paradoxical HS secondary to the use of these biological drugs have been described, with very few cases reported in the literature. The aims of this study are (1) to present 2 new cases of paradoxical HS and (2) to perform a systematic review of scientific evidence regarding paradoxical HS with TNF-α inhibitors. Material and Methods: This is a retrospective study in which we searched all the cases of paradoxical HS secondary to the use of TNF-α inhibitors published in the literature and included two additional cases observed in our clinical practice. Results: A total of 34 patients under TNF-α inhibitor treatment were included (adalimumab = 21; infliximab = 9; etanercept = 4). The median delay from exposure to TNF-α inhibitor and the development of paradoxical HS was 12 months (range 1–72). The majority of patients were Hurley stage II (58.8%). Clinical improvement and complete remission were more frequent when the TNF-α inhibitor was stopped or switched to another biological agent with a different therapeutic target rather than maintenance or change to another TNF-α inhibitor. Conclusions: Paradoxical HS is an unusual adverse effect of TNF-α inhibitors. When this adverse effect appears, interruption or substitution of treatment is associated with a better clinical outcome.