Encyclopedia > Autoimmune polyendocrinopathy syndrome, type I
In medicine, autoimmune polyendocrine syndromes are a heterogenous group of rare diseases characterised by autoimmune activity against more than one endocrine organs, although non-endocrine organs can be affected.
There are three "autoimmune polyendocrine syndromes", and a number of other diseases which have endocrine autoimmunity as one of their features.
The syndromes
Type 1 Autoimmune polyendocrine syndrome, type 1 is also known as the candidiasis_hypoparathyroidism-Addison's disease-syndrome after its main features: As opposed to type 2, this syndrome inherits in an autosomal recessive fashion and is due to a defect in AIRE ("autoimmune regulator"), a gene located on the 21st chromosome. Normal function of AIRE, a transcription factor, appears to be to confer immune tolerance for antigens from endocrine organs.
Type 2 Autoimmune polyendocrine syndrome, type 2 (also known as "Schmidt's syndrome") is more heterogenous, occurs more often and has not been linked to one gene. Rather, patients are at a higher risk when they carry a particular HLA genotype (DQ2, DQ8 and DRB1*0404).
Features of this syndrome are:
- Addison's disease
- hypothyroidism
- diabetes mellitus (type 1)
- less common associations:
Some researchers favour splitting this syndrome into three distict syndromes (numbering 2, 3 and 4), but research evidence for these distinct combinations is not convincing.
XPID The most serious but rarest form is the X-linked polyendocrinopathy, immunodeficiency and Down's syndrome) increase the risk of endocrine autoimmunity POEMS syndrome - the E is for endocrinopathy; the cause is a paraprotein excreted by a plasmacytoma or multiple myeloma; other features are polyneuropathy, organomegaly (hepatomegaly and splenomegaly), M-protein (paraprotein) and skin changes. Several very rare diseases.
Management In principle, the component diseases are managed as usual. The challenge is to detect the possibility of ane of the above syndromes, and to anticipate other manifestations. For example, in a patient with known Type 2 autoimmune polyendocrine syndrome but no features of Addison's disease, regular screening for antibodies against 21-hydroxylase (a feature of Addison's) may prompt early intervention and hydrocortisone replacement to prevent characteristic crises.
Sources - Eisenbarth GS, Gottlieb PA. Autoimmune polyendocrine syndromes. N Engl J Med 2004;350:2068_79.
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