Altered gut microbiome in fibromyalgia: Systematic review of genomic and metabolomic bacterial findings

Disruption of the gut microbiome has been implicated in several human disorders, including fibromyalgia, a musculoskeletal disorder characterized by widespread chronic pain and significant impairment of quality of life. Although it has been extensively studied, the results have been inconclusive. This systematic review aimed to analyze the available clinical evidence on the relationship between the altered gut bacterial microbiome and fibromyalgia, considering the microbiota gut brain axis and the use of omics. We searched Medline (Ovid), Scopus, Embase, Web of Science and Google Scholar, including observational studies in adults diagnosed with fibromyalgia, applying molecular, genetic, genomic and metabolomic techniques. The methodological quality was evaluated with tools from the Joanna Briggs Institute and the results were integrated into a narrative synthesis. Of the 732 studies initially identified, 11 fit the inclusion criteria, including a total of 455 patients with fibromyalgia and 385 controls, aged between 30 and 60 years. The overall certainty of the evidence is low to moderate, with greater strength for β-diversity, SCFAs, and the clinical manifestations of pain, fatigue, mood disturbances, and cognitive dysfunction supported by high-resolution techniques. Findings based solely on 16S have low certainty, supporting plausible associations between bacterial gut dysbiosis and fibromyalgia. Challenges such as methodological standardization and control of confounding factors, multi-omics, interdisciplinary and collaborative research are necessary to overcome the gaps in basic research and move towards translational research. • Gut dysbiosis is associated with alterations in microbiota gut brain axis pathways that may contribute to central sensitisation in fibromyalgia. • Advanced sequencing and machine learning reveal gut microbial patterns with potential diagnostic value in fibromyalgia. • Metabolomics is beginning to show the role of bacterial metabolites in the pathophysiology of fibromyalgia. • Longitudinal, methodologically robust multi-omics studies are needed to advance biomarker discovery and enable personalized therapies in fibromyalgia.