Exploring the Gut Microbiome's Association in Psoriasis and Psoriatic Arthritis: A Scoping Review

Psoriasis (PsO) and psoriatic arthritis (PsA) are chronic inflammatory conditions treated with primarily immune-modulating medication. However, interest is growing in gut microbiome therapies. Studies have reported altered gut microbiota in PsO/PsA and explored probiotics and fecal microbiota transplantation (FMT) as potential therapies. This review synthesizes global studies on the microbiome's associations in PsO/PsA.

We conducted a scoping literature review to understand the association between gut microbiota in PsO and PsA patients. Pubmed was used to identify 4,126 published manuscripts between 2015-2025. Thirty studies were included, encompassing 749,275 participants, with balanced gender representation and ages ranging from 18 to 76 years. These studies included 21 case-control studies, 1 case-series, 2 genome-wide analyses, 5 clinical trials, and 1 retrospective review.

Eighteen studies reported significant gut microbiome differences in PsO/PsA vs healthy controls. Variation in the Firmicutes/Bacteroides (F/B) ratio was of interest, with one study suggesting a low F/B ratio and five studies suggesting an elevated F/B ratio in PsO. A higher F/B ratio was linked to increased acetate production. Acetate and propionate, key short-chain fatty acids (SCFAs), were associated with modulation of the IL-23/Th17 axis in psoriasis and activation of keratinocytes. The role of therapeutics targeting the gut microbiome was explored. Ustekinumab and tofacitinib altered gut microbiome composition. Probiotic and FMT interventions showed mixed outcomes. Six of eight probiotic studies reported increased SCFA producing species and/or reduced inflammatory markers. FMT improved immune markers in mice but had no significant benefit in human trials.

Alterations in the microbiome linked to inflammation and immune response, suggest the microbiome as a potential therapeutic target for PsO/PsA.