RESUMEN
OBJECTIVE: The aim of this study was to perform a systematic review and meta-analysis answering the following questions: (a) "What is the prevalence and risk of oral lichen planus among patients with diabetes mellitus?" and (b) "What is the prevalence and risk of diabetes mellitus among patients with oral lichen planus?". MATERIAL AND METHODS: A bibliographic search was conducted in PubMed/Medline and Scopus database from 1966 to March 2018, using the following terms: "Lichen planus" AND "Diabetes mellitus" AND "Prevalence" AND "Oral mucosal lesions". RESULTS: Twenty-two studies were included in this review. Twelve studies assessed the prevalence of diabetes mellitus among patients with lichen planus. The prevalence reported ranges from 1.6% to 37.7% with a relative risk of 2.432. Ten studies assessed the prevalence of lichen planus among patients with diabetes mellitus which showed a prevalence of lichen planus ranging from 0.5% to 6.1% with a relative risk of 1.4. CONCLUSIONS: Contradictory results were found when analyzing the relationship between lichen planus and diabetes mellitus. Diverse factors should be considered when studying this association for a correct interpretation of results. Diabetes mellitus has high prevalence and morbidity, which is why new case-control studies are needed to further investigate this association.