Addison's disease is a rare endocrine disorder where the adrenal glands do not produce enough hormones. It is caused by damage to the adrenal cortex, which can be from an autoimmune response, infection, tumors, or other issues. Symptoms include weakness, fatigue, weight changes, and hyperpigmentation of skin. Left untreated, it can cause an Addisonian crisis with severe low blood pressure and other dangerous symptoms. Treatment involves lifelong hormone replacement therapy and monitoring, especially during times of stress. Nursing care focuses on monitoring the patient, educating on treatment and crisis signs, and ensuring fluid and electrolyte balance.