An autoimmune disease is a condition in which the immune system mistakenly attacks the body’s own healthy tissues, mistaking them for invaders. Examples include multiple sclerosis, rheumatoid arthritis, lupus and type 1 diabetes. Symptoms vary widely and can flare and fade unpredictably, which often makes diagnosis slow and difficult. Treatments usually aim to calm or suppress the immune response and manage symptoms, rather than cure the underlying condition.