Lupus is a chronic autoimmune disease in which the immune system mistakenly attacks healthy tissues and organs, causing widespread inflammation. The most common form, systemic lupus erythematosus (SLE), can affect the skin, joints, kidneys, heart, lungs, brain, and blood cells. Symptoms vary widely and may include fatigue, joint pain and swelling, skin rashes (often a butterfly-shaped rash across the cheeks), fever, and sensitivity to sunlight. The disease often follows a pattern of flare-ups and periods of remission. The exact cause is not fully understood but involves a combination of genetic susceptibility, hormonal influences, and environmental triggers. Because lupus can affect multiple organ systems, it may produce a broad range of symptoms and requires careful medical evaluation for diagnosis.