Approximately 50% of lupus patients develop lupus nephritis, which is inflammation in the kidney vessels. The same pathogens cause lupus and lupus nephritis, and the pathogens create abnormal antibodies and abnormal proteins, which trigger an immune system attack, inflammation and vasculitis.  Lupus patients treated with steroids and immune-suppressants are at risk for developing lupus nephritis and decreased kidney function, within five years.

Chlamydia trachoma causes reproductive disease, urethritis, and lupus; and can ascend the urinary system to the kidney. Chlamydia pneumonia can cause lupus, cardiovascular disease, and small-vessel vasculitis anywhere in the body.  Streptococcus-M deposits harmful M-proteins and causes vasculitis, and a similar disease known as glomerulonephritis.

Different immortal pathogens originating in the gastrointestinal, urinary or reproductive tract can cause lupus.  Steroids and immunosuppressant drugs potentiate the underlying infections, and can trigger lupus nephritis.