Alterations in the cutaneous microbiome of patients with psoriasis and psoriatic arthritis reveal similarities between non-lesional and lesional skin.

Objectives: To investigate the cutaneous microbiome spanning the entire psoriatic disease spectrum, and to evaluate distinguishing features of psoriasis (PsO) and psoriatic arthritis (PsA).
Methods: Skin swabs were collected from upper and lower extremities of healthy individuals and patients with PsO and PsA. Psoriatic patients contributed both lesional (L) and contralateral non-lesional (NL) samples. Microbiota were analysed using 16S rRNA sequencing.
Results: Compared with healthy skin, alpha diversity in psoriatic NL and L skin was significantly reduced (p<0.05) and samples clustered separately in plots of beta diversity (p<0.05). Kocuria and Cutibacterium were enriched in healthy subjects, while Staphylococcus was enriched in psoriatic disease. Microbe-microbe association networks revealed a higher degree of similarity between psoriatic NL and L skin compared with healthy skin despite the absence of clinically evident inflammation. Moreover, the relative abundance of Corynebacterium was higher in NL PsA samples compared with NL PsO samples (p<0.05), potentially serving as a biomarker for disease progression.
Conclusions: These findings show differences in diversity, bacterial composition and microbe-microbe interactions between healthy and psoriatic skin, both L and NL. We further identified bacterial biomarkers that differentiate disease phenotypes, which could potentially aid in predicting the transition from PsO to PsA.
Competing Interests: Competing interests: RHH: received consulting fees from Janssen ALN: served as a consultant for Janssen, UCB, AbbVie and Bristol-Myers Squibb; has an immediate family member who owns shares of stock in J&J, Eli Lilly, AbbVie and Pfizer JUS: served as a consultant for Janssen, Abbvie, Novartis, Sanofi, UCB and BMS.
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