Interaction between microbiome and host genetics in psoriatic arthritis.

Psoriatic arthritis (PsA) is a chronic inflammatory joint disease, seen in combination with psoriasis. Both genetic and environmental factors are responsible for the development of PsA, however little is known about the different weight of these two distinctive components in the pathogenesis of the disease. Genomic variability in PsA is associated with the disease and/or some peculiar clinical phenotypes. Candidate genes involved are crucial in inflammation, immune system, and epithelial permeability. Moreover, the genesis and regulation of inflammation are influenced by the composition of the human intestinal microbiome that is able to modulate both mucosal and systemic immune system. It is possible that pro-inflammatory responses initiated in gut mucosa could contribute to the induction and progression of autoimmune conditions. Given such premises, the aim of this review is to summarize immune-mediated response and specific bacterial changes in the composition of fecal microbiota in PsA patients and to analyze the relationships between bacterial changes, immune system, and host genetic background.