The Association Between Oral Lichen Planus and Diabetes Mellitus: A Scoping Review of the Evidence

OBJECTIVE: Oral lichen planus (OLP) is a chronic immune-mediated oral potentially malignant disorder. Three prior meta-analyses reported elevated diabetes mellitus (DM) prevalence in patients with OLP, but the evidence base has since expanded. This scoping review synthesised all available evidence on the OLP-DM association up to November 2025. STUDY DESIGN: PubMed/MEDLINE, Embase, Scopus, and the Cochrane Library were searched up to November 30, 2025 with no lower date limit, supplemented by backward citation searching. No study design restrictions were applied. Findings were synthesised thematically per PRISMA-ScR. RESULTS: Twenty-one sources from 11 countries were included, encompassing observational studies, Mendelian randomisation analyses, biochemical investigations, reviews, and case reports. DM prevalence in patients with OLP ranged from 9.7% to 24.5%, with the association specific to type 2 DM. Prediabetes was independently associated with OLP after multivariate adjustment. Mendelian randomisation provided causal evidence linking type 1 DM and elevated glycated haemoglobin to increased OLP risk. CONCLUSIONS: The OLP-DM association is consistent, biologically plausible, and extends to subclinical glycaemic dysregulation. Glycaemic assessment should be considered in patients with OLP presenting with oral or systemic features suggestive of metabolic dysregulation. Future research should prioritise longitudinal studies, intervention trials on glycaemic optimisation.