Paradoxical psoriasis is an exacerbation of, or new-onset, psoriasis associated with tumour necrosis factor inhibitors (TNFi). This interferon-mediated response differs from classical psoriasis, but a clinical definition and detailed immunologic understanding has yet to be established. Imaging Mass Cytometry (IMC) is a novel technology that enables cellular phenotyping while preserving tissue architecture by combining principles of flow cytometry and mass spectroscopy. Following PRISMA2020 guidelines, we performed a systematic review (n = 391) of clinical features of paradoxical psoriasis and a meta-analysis (n = 9514; 6 studies) on risk factors for its development in Inflammatory Bowel Disease (IBD). Additionally, we designed a 36 metal-conjugated panel of antibodies for IMC, to phenotype lymphocyte subsets (Th1, Th2, Th17, Treg), dendritic cells and other innate subsets. Panel development was performed with plaque psoriasis given the immunohistochemistry literature. In our systematic review, we showed that paradoxical eruptions were most often pustular (39.9%, 154/391) and plaque-type (38.9%, 152/391). In our random effects meta-analysis of observational studies on IBD patients (n = 6), we found that female sex (OR 1.46, 95% CI 1.09 – 1.97) and Crohn’s (vs. ulcerative colitis; OR 1.69, 95% CI 1.23 – 2.71) were associated with reaction development following TNF exposure. Results from IMC in plaque psoriasis (n = 7) demonstrated specific staining based on co-localization and dermatopathologist review. Biopsies demonstrated predominant Tcells (67.8% - 78.2%) mostly CD4+ (76.9% to 92.3%), with myeloid and endothelial co-localization. With a clearer clinical picture of paradoxical psoriasis and a validated antibody panel, future work will compare IMC of paradoxical psoriasis with classical plaque psoriasis and non-lesioned controls.

ESDR395 - Defining Paradoxical Psoriasis and Deep Tissue Immune Cell Profiling

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.