Lichen planus (LP) is a chronic inflammatory disease, mediated by T cells, with a multifactorial etiology, being associated with various diseases and systemic conditions. The objectives of this study are to determine, through the analysis of the literature, the casuistic or causal relationship in the concomitant presentation of Oral Lichen Planus (OLP) and other systemic diseases, and to analyze a series of cases treated at the University Hospital of Brasília (HUB) between 2015 and 2020. Methodology: This study was developed through a review of the literature published between 2016 and 2022, relating systemic diseases with OLP and the analysis of series of OLP cases treated at the HUB. Results: The review showed evidence of the relationship between OLP and Thyroid Disease (TD), Psychiatric Disease (PD), HPV virus and oxidative stress. Furthermore, it was observed that alterations in the oral bacterial microbiota are associated with the progression of OLP. Analysis of the case series identified a relationship between TD and PD with OLP. Conclusion: It is observed that there is strong evidence of the relationship between OLP and DT, DP, HPV virus, oxidative stress and the presence of periodontal bacteria in the oral cavity.