Given the mentioned phenotypical overlap of IPEX syndrome with a series of IEI (with or without immune dysregulation), Sanger sequencing of the FOXP3 gene is usually applied to selected cases, such as classical triad of symptoms, neonatal T1D, and intractable diarrhea in neonates with significant family history in the maternal lineage (including affected males, fetal hydrops, and multiple miscarriages of male fetuses) (1, 4, 91). Here, FOXP3 is linked to type 1 diabetes mellitus.