Inflammatory signals linking inverse, erythrodermic and chronic plaque psoriasis

Inverse and erythrodermic psoriasis are rare subtypes of psoriasis. Whereas the former is characterized by shiny erythematous non-scaly plaques in the body folds, the latter has widespread redness with fine scale, covering over 80% of the body-surface area, and can be life-threatening. Both are considered to be clinical subtypes of chronic plaque psoriasis, and often co-exist or evolve from plaque psoriasis (Boyd and Menter, 1989; Omland and Gniadecki, 2015), but the pathogenic mechanisms involved are unknown, and current treatments are frequently unsatisfactory. To assess shared and unique processes between chronic plaque, inverse, and erythrodermic psoriasis we analyzed archived formalin-fixed paraffin-embedded biopsies of clinically and histologically confirmed chronic plaque (n=12), inverse (n=40) and erythrodermic psoriasis cases (n=30) and healthy control skin (n=20) using Affymetrix ST 2.1 Arrays. Compared with healthy skin, psoriatic plaque lesions yielded 2450 differentially expressed genes (DEGs) (FDR, p<0.05), inverse psoriasis lesions yielded 408 DEGs (FDR, p<0.05) and erythrodermic psoriasis lesions yielded 447 DEGs (FDR, p<0.05). In total 294 genes were found to be shared among the three disease subtypes (FDR, p<0.05). While the overlap only accounted for 12% of the DEGs in chronic plaque psoriasis, it accounted for 66% and 72% of DEGs in erythrodermic and inverse psoriasis respectively. 20 normal healthy skin biopsies, 12 chronic plaque psoriasis, 40 inverse psoriasis, 30 erythrodermic psorasis