STAT1 gain-of-function mutations do not affect the expression of FOXP3 or CTLA-4 or the development of Tregs.151 Despite the phenotypic overlap between APECED and immunodeficiency due to STAT1 gain of function, there is no evidence of a pathomechanistic connection between these two monogenic disorders. This evidence concerns the gene STAT1 and Immunodeficiency.