We detected a difference in the expression of the recent-thymic emigrant marker CD31 within CD4+CD25+FOXP3+ cells, where the expression was lower in APS-1 patients compared to healthy controls (mean patients 0.6%, mean controls 1.4%, p = 0.0369, Figure 4B). This evidence concerns the gene PECAM1 and autoimmune polyendocrine syndrome type 1.