Autoimmune disease refers to a group of disorders in which the immune system mistakenly attacks the body’s own healthy tissues, identifying them as foreign threats. This abnormal immune response can affect virtually any organ or system, including the joints, skin, thyroid, nervous system, blood vessels, or digestive tract. Common examples include rheumatoid arthritis, lupus, multiple sclerosis, type 1 diabetes, and Hashimoto’s thyroiditis. Symptoms vary depending on the condition but often involve chronic inflammation, fatigue, pain, swelling, and organ dysfunction. The exact cause is not fully understood but is believed to involve a combination of genetic predisposition, environmental triggers, infections, and immune system dysregulation. Treatment typically focuses on reducing inflammation, suppressing inappropriate immune activity, and managing symptoms to prevent long-term tissue damage.