Autoimmune diseases occur when the body's immune system mistakenly attacks its own tissues and organs. Normally, the immune system defends against foreign invaders like bacteria and viruses, but in autoimmune disorders, it fails to distinguish between healthy cells and harmful agents, leading to inflammation and damage. There are over 80 different autoimmune diseases, affecting various parts of the body. Common examples include rheumatoid arthritis, lupus, type 1 diabetes, multiple sclerosis, and Crohn's disease.

The exact cause of autoimmune diseases is not fully understood but is believed to involve a combination of genetic predisposition and environmental triggers, such as infections or certain medications. Symptoms vary depending on the affected area but often include fatigue, joint pain, skin rashes, and digestive issues. Diagnosis typically involves blood tests, imaging, and clinical evaluation. While there is no cure, treatment focuses on managing symptoms, reducing inflammation, and suppressing the immune response with medications like corticosteroids or immunosuppressants.