Lupus nephritis is inflammation of the kidney caused by systemic lupus erythematous (SLE). Also called lupus, SLE is an autoimmune disease. Lupus nephritis happens when lupus involves the kidneys. Up to 60% of lupus patients are likely to develop lupus nephritis. When the kidneys get inflamed, they can’t function normally and can leak protein. If lupus nephritis is not controlled, it can lead to kidney failure.