Normally the immune system learns to ignore the body's own tissues, a state called tolerance. In autoimmune disease tolerance breaks down, and antibodies or T cells attack healthy tissue.
How tolerance fails
Genes, hormones and triggers such as infections combine to break tolerance. Many autoimmune diseases are more common in women and often run in families.
Organ-specific disease
Some target one organ, as in type 1 diabetes (insulin-making beta cells), Hashimoto thyroiditis and Graves disease (thyroid), and multiple sclerosis (myelin in the brain and spinal cord).
Systemic disease
Others affect many organs, as in systemic lupus erythematosus (skin, joints, kidneys, blood) and rheumatoid arthritis (joint linings and beyond). Symptoms often come and go in flares.
Tests and treatment
Autoantibody tests such as ANA, rheumatoid factor and anti-CCP support the diagnosis, along with CRP and ESR. Treatment calms the immune system with steroids and immune-modifying drugs, or replaces what was lost, such as insulin or thyroid hormone.
At the bedside
Ask about joint pain and morning stiffness, rashes, fatigue and family history, since autoimmune disease often starts with vague symptoms. Patients on immunosuppressants are prone to infection, so take any fever seriously.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).