Systemic lupus erythematosus (SLE) is a disease of unknown origin that can affect organs and cause severe damage. Lupus is diagnosed through biopsies and laboratory examinations; however, certain clinical characteristics and the presence of lesions can help with early diagnosis and improve the disease prognosis. SLE patients generally receive immunosuppressants that may cause systemic implications---such as suture dehiscence, increased risk of infection, and delayed healing--that deserve specific attention during dental treatment. This article presents a case of a SLE patient with oral manifestations: ulcerative lesions in the mouth and development of lupus nephritis. This article seeks to emphasize the importance of recognizing the lesions related to SLE, which may help the dentist to establish an early diagnosis.