Systemic lupus erythematosus (SLE) can vary in severity. The main criterion for determining whether it is mild or severe is to check whether SLE has involved important visceral organs, such as the lungs, the heart, and most commonly, the kidneys, as well as the most severe form, neuropsychiatric lupus. If a patient shows involvement of the aforementioned visceral systems, then lupus is considered to be relatively severe, and may sometimes even threaten the patient’s life. However, if lupus does not involve the visceral systems, it is considered to be mild.