Porphyromonas gingivalis as a keystone pathogen in systemic diseases.

Porphyromonas gingivalis (P. gingivalis) is a Gram-negative anaerobic bacterium recognized as a keystone pathogen in periodontitis. Beyond its established role in periodontal tissue destruction, accumulating evidence links P. gingivalis to several systemic conditions, including cardiovascular disease, Alzheimer's disease, rheumatoid arthritis, diabetes mellitus, and adverse pregnancy outcomes. This review synthesizes current evidence on how P. gingivalis may contribute to systemic disease beyond the oral cavity, with particular emphasis on its virulence factors, including gingipains and lipopolysaccharide, and the pathways linking periodontal infection to pathological processes in distant organs. We discuss how hematogenous dissemination, immune-evasion mechanisms, and chronic inflammatory responses may mediate these systemic effects. A clearer understanding of these associations may inform integrated approaches to periodontal care and systemic disease management.