Multifaceted Role of Vitamin D in the Pathogenesis and Clinical Management of Oral Lichen Planus: Current Evidence and Research Perspectives

Oral lichen planus (OLP) is a chronic, immune-mediated inflammatory disorder of the oral mucosa, primarily involving T lymphocyte activity. It is recognized by the World Health Organization as an oral potentially malignant disorder due to its established risk for malignant transformation. Although OLP has been the subject of extensive research, its pathogenesis remain partially understood. Vitamin D, a fat-soluble hormone essential for calcium-phosphorus homeostasis and immunological regulation, has emerged as a significant factor in the onset, progression, and clinical course of OLP. This review systematically examines the association between vitamin D-related local metabolic pathways and the oral mucosal microenvironment, synthesizing epidemiological evidence from diverse geographic regions that support an association between vitamin D deficiency and the occurrence of OLP. The molecular mechanisms by which vitamin D modulates OLP are discussed within a comprehensive framework including cellular protection, immune modulation, and regulation via non-coding RNAs. In addition, recent advances in the clinical application of vitamin D is summarized, particularly in relation to its potential role in non-invasive diagnostics and as an adjunctive therapy for OLP. Unresolved questions and areas of debate in current research are critically evaluated. Based on contemporary high-quality evidence, future research directions are proposed, emphasizing the need for individualized therapeutic strategies through multicenter, large-scale randomized controlled trials. Additional exploration of the interactions among vitamin D/vitamin D receptor signaling pathways, non-coding RNA networks, and the gut microbiota is recommended to enhance mechanistic insights and optimize clinical management strategies for individuals with OLP.