Autoimmune polyglandular syndrome type 2 is an autoimmune disorder that affects many hormone-producing (endocrine) glands. It is characterized by the presence of Addison's disease along with autoimmune thyroid disease and/or type 1 diabetes. Affected individuals may also have problems with other endocrine glands and other common features include primary hypogonadism, myasthenia gravis, and celiac disease. Autoimmune polyglandular syndrome type 2 is diagnosed in adulthood, typically around age 30. The cause of autoimmune polyglandular syndrome type 2 is unknown, although it may involve a combination of genetic and environmental factors. This condition occurs more often in women than men. About 10% of patients with APS-2 and Addison’s disease had a relative with adrenal insufficiency, and about 10% of patients with APS-2 and type 1 diabetes had a sibling with the same disease, and, or with autoimmune thyroid disease.

Currently, there are no unique tests to detect APS-2, but testing for autoantibodies may be helpful in assessing disease risk, since the relevant autoantibodies (such as antibodies to thyroid peroxidase in autoimmune thyroid disease, or to glutamic acid decarboxylase in type 1 diabetes) are frequently detectable years before disease onset. Treatment is mainly with hormone replacement therapy.

While the cause of polyglandular autoimmune syndrome type 2 is not fully understood, it usually results from an autoimmune reaction, probably triggered by a virus or other environmental antigen. There is some evidence of an association between diabetes or hypothyroidism and congenital rubella infection. Other cases may result from immune stimulation caused by certain dietary proteins. In general, there is an association with certain genes coding for proteins involved with the immune system, particularly of the major histocompatibility complex. For example, patients with APS-2 who are at risk for celiac disease generally have variants in DR3-DQ2 and DR4-DQ8, which also confer a risk of type 1 diabetes, autoimmune thyroid disease, and Addison’s disease.

Although most cases of autoimmune polyglandular syndrome type 2 are sporadic, some clinical researchers believe that there is a familial or hereditary trait associated with it. Genetic factors, perhaps related to HLA subtypes, appear to increase susceptibility to this condition. In addition, several different types of inheritance (autosomal recessive, autosomal dominant, multifactorial) have been reported, suggesting that it may involve a complex interaction among many genes. There have been several reports of multiple family members with one or more endocrine deficiencies.