The literature points to mutations in FOXP3 as the main genetic factor that interferes with Treg function; however, one patient with non-immunodeficiency, polyendocrinopathy, and enteropathy X-linked (IPEX) autoimmune enteropathy had no mutations in the FOXP3 locus and did not exhibit chronic reduction of Treg in the bloodstream or accumulation of FOXP3+ Treg in the inflamed duodenum during the active stage of disease, which could have contributed to the loss of local immune control. This evidence concerns the gene FOXP3 and polyendocrinopathy.