Pregnancy outcome in poly-autoimmune disorders. The case of APECED syndrome

Autoimmune polyendocrinopathy-candidiasis–ectodermal dysplasia (APECED) or PAS I is a rare monogenic disorder affecting 10 people/million characterized by different loss of-function mutations on the AIRE gene (1). The AIRE gene encodes a protein representing a nonconventional transcrip tion factor, predominantly expressed in the thymus, which localizes to chromatin encompassing the target genes and activates, through histones binding, the complexes involved in the initiation of gene transcription (2). It induces ectopic expression of self-antigens in thymus cells that are other wise silenced and restricted to other tissues. Ultimately, the AIRE gene determines the central tolerance through the deletion of autoreactive thymocytes and modulates the per ipheral tolerance through the positive selection of regula tory T cells (Tregs) (1). Its loss of function seems to enable the escape of autoreactive T clones from the thymus to cir culation, where poorly efficient Tregs may not ensure per ipheral tolerance (3). Almost all developmental tissues are expressed in the thymus under the control of AIRE (3), and therefore pregnancy represents a primary event for human immune system.