The Gut-Joint Connection: Microbiome's Role in Rheumatic Disease.

The human gut microbiome is a pivotal regulator of systemic immunity and a central factor in the pathogenesis of rheumatic diseases. An imbalance in this microbial community, known as "dysbiosis," can trigger and perpetuate autoimmune responses through the "gut-joint axis." A key mechanism underpinning this connection is increased intestinal permeability ("leaky gut"), which facilitates the translocation of microbial products like lipopolysaccharide into the systemic circulation, thereby provoking chronic inflammation. Concurrently, dysbiosis disrupts the critical homeostatic balance between pro-inflammatory Th17 cells and regulatory T cells, an immunological hallmark of conditions such as rheumatoid arthritis (RA), ankylosing spondylitis, and systemic lupus erythematosus (SLE). Specific microbial signatures, including the expansion of Prevotella copri in RA and Ruminococcus gnavus in SLE, are emerging as potential diagnostic biomarkers. This deeper understanding is paving the way for innovative therapeutic strategies. Interventions aimed at modulating the gut microbiota, such as targeted diets, probiotics, prebiotics and fecal microbiota transplantation, represent a promising frontier for the personalized management of rheumatic diseases. This review explores the foundational mechanisms linking the microbiome to autoimmunity and discusses the clinical potential of harnessing the gut-joint axis to improve patient outcomes.