Lupus is an autoimmune disease where the immune system mistakenly attacks the body's own tissues. The most common form is systemic lupus erythematosus.
Common symptoms
Lupus can cause fatigue, joint pain, rash, fever, mouth sores, hair loss, chest pain, kidney problems, blood changes, or sensitivity to sunlight.
Why it is variable
Lupus can be mild in one person and serious in another. Symptoms can flare and then calm down, and different organs can be involved.
Because lupus can resemble other autoimmune or inflammatory diseases, diagnosis usually combines symptoms, exam findings, and lab testing.