Gut microbiota differences between psoriatic arthritis and other undifferentiated arthritis: A pilot study

Background: Psoriatic arthritis (PSA) is a form of immune-mediated inflammatory arthritis that predominantly begins with enthesitis. Studying the gut microbiota of PSA patients may offer new insights into the pathogenesis of enthesitis, compared to other arthritis. We designed a prospective study to examine gut microbiome of patients with PSA, primarily with enthesitis and dactylitis, and compared the data with other undifferentiated types of arthritis (NO PSA) patients, without enthesitis or dactylitis. Methods: We enrolled 9 PSA patients and 10 NO PSA patients in this study. We excluded rheumatoid arthritis, systemic lupus erythematosus, Sjogren syndrome, systemic sclerosis, mixed connective tissue disease, polymyositis, dermatomyositis, ANCA-associated vasculitis, and gouty arthritis patients. The fecal samples were investigated using 16S rRNA amplicon sequencing, followed by bioinformatics and statistical analyses. Results: None of the available objective clinical laboratory data could differentiate PSA group from the NO PSA subgroup. The microbiota result shows that Family: XIII_AD3011 is significantly higher in NO PSA patients' than in PSA patients' stool samples (P = .039). Megasphaera elsdenii in the PSA group was 10,000 times higher than in the NO PSA group. Our results demonstrated high intragroup homogeneous and high intergroup heterogeneous microbiota. The clinical symptoms of either enthesitis or dactylitis are associated with higher presence of specific microbiota in the current study. The PSA and other undifferentiated arthritis could be differentiated with microbiota analysis. In the future, a larger cohort and thorough biochemical study are needed for confirmation. The microbiota is different between PSA and NO PSA patients, and the species could be used as a differential diagnostic tool between these 2 diseases. The clinically available serum markers may not be enough to reflect the details of patients with different patterns of arthritis. Megasphaera elsdenii species could be a link between gut flora and enthesitis and/or dactylitis clinically in PSA. We confirm the fact that the Bifidobacterium longum correlates negatively with eosinophils.