The autoimmune polyendocrinopathy-candidiasis-ectodermal-dystrophy (APECED) syndrome, also known as autoimmune polyendocrinopathy syndrome type 1 (APS1), is an autosomal recessive disease characterized by a classic triad of chronic mucocutaneous candidiasis, hypoparathyroidism, and adrenal cortical failure. Mutations in the AIRE gene
Table 2 Major Clinical Features of the IPEX Syndrome (63)
Hemolytic anemia Thrombocytopenia Lymphadenopathy Hepatospenomegaly Recurrent infections are thought to be responsible for this syndrome, which is found in greatest frequency among Iranian Jews, Sardinians, and Finns (55). Although T1DM is relatively uncommon in APS Typel (approximately 1% of affected probands), a publication on a series of Finnish patients with APECED reported a 12-fold higher prevalence of diabetes compared to the general population (56). The association between diabetes and both autoimmune adrenal insufficiency and thyroiditis is considerably greater in patients with APS type 2, also known as Schmidt syndrome (57), or Carpenter syndrome, so called when all the three conditions are present (58). Autoimmune diabetes is present in 20% to 50% of subjects with the APS type 2, and usually presents at an earlier age than either Addison's disease or thyroid disorders (59,60). As with classical type 1A diabetes, and similar to what is seen in other isolated autoimmune disorders, there is clear evidence of both humoral and cellular autoimmunity as manifested by the presence of organ-specific autoantibodies and CD8+ predominant lymphocytic infiltration (60). Addison's disease was also found to be linked to HLA DR3 and DR4 haplotypes, both independently of its association with T1DM (HLA DR3/DBQ1*0201), and in the presence of ICA (HLA DR4/DBQ1*0302) (61). Because a family history of APS type 2 is rare, it may be prudent to periodically screen patients who develop autoimmune organ damage for autoantibodies to other conditions, or at the very least to closely monitor for signs and symptoms of other autoimmune diseases.
The immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare, autosomal dominant X-linked condition affecting male children usually in the neonatal period, characterized by early onset T1DM and severe enteropathy as well as by autoimmune skin disease, hypothyroidism, and variable other autoimmune manifestations (Table 2) (62-65). In the majority of cases, the condition is linked to mutations in the human FOXP3 gene (66), which is thought to be an essential player in the regulation of T-cell activation. Mutations in this gene result in deficiencies of T regulatory cells (CD4+CD25+ T-cells), which are essential in controlling the activity of antigen-stimulated T cells. The relationship and similarities among these three autoimmune syndromes is illustrated in Table 3 and Figure 3.
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