A woman had ulcerative lichen planus of the feet. Results of laboratory tests indicated lupus erythematosus, but there were no visceral symptoms. These findings suggest that there is a certain interrelation with the skin disease and support the theory that the cause of lichen planus is of an autoimmune nature.
Thormann J. Ulcerative Lichen Planus of the FeetA Case in Which the Serological Findings Suggested Systemic Lupus Erythematosus. Arch Dermatol. 1974;110(5):753-755. doi:10.1001/archderm.1974.01630110047011