Systematic lupus erythematosus (SLE), or lupus, is an autoimmune disease that affects around 50 out of 100,000 people. It is difficult to diagnose and is easily confused with other diseases. Symptoms include a red rash, painful and swollen joints, fever, chest pain, hair loss, mouth ulcers, swollen lymph nodes and feeling tired.
Lupus nephritis, where the disease causes inflammation of the kidneys, is the most common severe manifestation of SLE. It is routinely diagnosed using renal biopsies which are invasive and can lead to complications.