In 2001, a mutation in the Foxp3 gene, an X-linked transcription factor, was identified as the causative mutation in the Scurfy mouse, which displays a severe autoimmune phenotype.6,7 A mutation in Foxp3 was then found to be responsible for the human disease, immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX).8 This disorder is associated with autoimmune enteropathy, dermatitis, nail dystrophy, autoimmune endocrinopathies, and autoimmune skin conditions. Here, FOXP3 is linked to immune dysregulation-polyendocrinopathy-enteropathy-X-linked syndrome.