Lichen planus 扁平苔藓( lichen Planus,LP) common cutaneomucosal diseases Wilson first report(1869) about 44% skin lichen planus associated With oral mucosa lesion Some patients the lesion only involves oral mucosa Department of Oral Pathology, Shandong UniversityDepartment of Oral Pathology, Shandong University 2 Lichen planus 扁平苔藓 (lichen Planus，LP) common cutaneomucosal diseases Wilson first report (1869) About 44% skin lichen planus associated with oral mucosa lesion Some patients the lesion only involves oral mucosa