Decoding the Gut Microbiome in Primary Sjögren’s Syndrome and Primary Biliary Cholangitis: Shared Dysbiosis, Distinct Patterns, and Associations with Clinical Features

This study aimed to analyze gut microbiome similarities and differences between primary biliary cholangitis (PBC) and primary Sjögren's syndrome (pSS), exploring potential associations with disease pathogenesis. High-throughput sequencing of the 16S rRNA gene was performed on fecal samples from 100 subjects (PBC: 38; pSS: 42; HC: 20) to compare the composition, diversity, and key microbial markers, examining associations with clinical indicators. The gut microbiome of PBC and pSS patients exhibited reduced alpha diversity (<i>p</i> < 0.05) and decreased abundance of the Bacteroides genus (both <i>p</i> < 0.001). While the majority of differentially abundant species were similar in PBC and pSS, unique imbalances were noted: Actinobacteria was elevated in pSS, whereas Proteobacteria was higher in PBC (<i>p</i> < 0.05). At the species level, a higher relative abundance of <i>Ruminococcus torques</i>, <i>Clostridium celatum</i>, and <i>Lactobacillus vaginalis</i> was identified in PBC patients, with positive correlations observed with key clinical indicators such as liver enzymes and TBA. In pSS patients, <i>Faecalibacterium prausnitzii</i> showed a negative correlation with GGT and ALT. Although PBC and pSS shared many similarities in their gut microbiome's composition and diversity, indicating common mechanistic microbial influences on their pathogenicity, distinct microbial profiles correlated with clinical indicators in each disease, highlighting specific microbiome-disease interactions that may underlie their differential pathogenesis.