Blood single cell transcriptome of paradoxical eczema in psoriasis patients treated with biologics
Biologics targeting the tumour necrosis factor (TNF) and interleukin (IL)-17/23 axis are highly effective treatments for psoriasis but can result in cutaneous adverse events. The pathogenesis of paradoxical eczema, the occurrence of an atopic dermatitis phenotype after biologic initiation in people with psoriasis, is unknown. Using single cell RNA-seq and mass cytometry, we found increased expression of TNF, interferon (IFN)-? and IFN-a and their signalling pathways in paradoxical eczema case cell clusters compared with matched psoriasis controls. Genetic variants influencing expression of TNF pathway genes were associated with paradoxical eczema in a separate genotyped cohort, and this association was independent of known atopic risk loci. This suggests that paradoxical eczema has a predominantly type 1 systemic inflammatory signature, and that genetic susceptibility to aberrant TNF pathway signalling could contribute to development of this phenotype during biologic treatment. Overall design: Peripheral blood mononuclear cells (PBMCs) were obtained from 3 patients with psoriasis who developed paradoxical eczema, and 3 matched psoriasis controls, and analysed with single cell (sc)RNA-seq.