An autoimmune polyendocrinopathy with Addison disease as its main characteristic, in conjunction with autoimmune thyroid diseases and/or diabetes mellitus type 1. Associated autoimmune thyroid diseases include Hashimoto thyroiditis and Graves disease. Other conditions that may appear include hypothyroidism, hyperthyroidism, myasthenia gravis, hypogonadism, and celiac disease. Vitiligo may appear in up to 50% of cases. Etiology is not well understood, although some cases of autosomal-dominant inheritance have been observed. The syndrome is 3 times more common in females. Onset is in adulthood, most commonly around age 30. Treatment includes hormone replacement.