Lupus is an inflammatory autoimmune disease that can affect multiple organ systems. As such, it can be diagnosed because of multiorgan or constitutional symptoms, but frequently medical treatment is sought only when there is clinical involvement of a particular organ or system, even if established--but undiagnosed--systemic disease is already present. The authors present the case of a patient admitted to a cardiology unit for acute pericarditis, in whom the diagnosis of systemic lupus erythematosus was made, and highlight the need to consider cardiac involvement in systemic diseases.