An autoimmune disease is a health condition in which the immune system mistakenly attacks the body's own healthy cells and tissues instead of defending against harmful invaders like viruses and bacteria. This occurs because the immune system cannot distinguish between foreign substances and the body's own cells, leading to damage and dysfunction in various organs or tissues

. There are more than 80 to over 100 different autoimmune diseases, affecting nearly any part of the body. Examples include rheumatoid arthritis, lupus, type 1 diabetes, multiple sclerosis, psoriasis, and inflammatory bowel diseases like Crohn's disease

. Symptoms vary widely depending on the disease and affected organs but often include fatigue, low-grade fever, joint pain, and skin rashes

. The exact cause of autoimmune diseases is unclear, but they are believed to result from a combination of genetic predisposition and environmental triggers such as infections, toxins, certain medications, and lifestyle factors like smoking or obesity

. Women are more commonly affected than men, and having one autoimmune disease increases the risk of developing another

. Autoimmune diseases are typically chronic and may be managed by treatments that suppress or modulate the immune system to reduce its attack on the body, though cures are generally not available

. In summary, an autoimmune disease is a malfunction of the immune system causing it to attack the body's own healthy tissues, leading to a wide range of chronic conditions with diverse symptoms and causes