FOXP3 and Failure to thrive: IPEX syndrome results from a mutation with the FOXP3 gene causing severe deficiency or absence of T regulatory cells that leads to polyendocrinopathy as well as other autoimmune manifestations and failure to thrive.5 As shown in this patient who developed gastrointestinal and dermatological symptoms shortly after diagnosis of diabetes mellitus, the progression of the disease can be quite quick with new manifestations occurring in rapid succession.