Autoimmune diseases occur when the immune system mistakenly attacks the body’s own tissues, thinking they are foreign invaders. This can lead to inflammation and damage in various parts of the body. Common autoimmune diseases include rheumatoid arthritis, lupus, type 1 diabetes, and multiple sclerosis. The exact cause of autoimmune diseases is not well understood, but factors such as genetics, environmental triggers, and infections may play a role. Symptoms can vary widely depending on the specific disease but often include fatigue, pain, swelling, and skin rashes.