Lip round or oval erythema is also known as discoid lupus erythematosus. The cause of discoid lupus erythematosus is unknown, and it is mostly thought to be an autoimmune disease probably related to genetic factors as well as various stimulating factors. 1. Genetic factors: A family history can be found in some patients and has been confirmed by the study of human leukocyte antigen (HLA). 2. Stimulating factors: mostly predisposing factors, including sun exposure, infections (e.g., viruses, tuberculosis, streptococci or lesions), endocrine disorders, cold stimulation, mental stress, and drugs (e.g., hydrazidiazide). The pathogenesis may be: the formation of the body’s own antigens, loss of recognition by immunologically active cells and dysregulation of its own stabilization mechanisms under the influence of triggers and genetic factors, and the production of large amounts of anti-self tissue antibodies. The combination of antigens and antibodies in the patient’s blood forms antigen-antibody complexes, which are deposited in the tissues and cause lesions.