FOXP3 and diabetes mellitus: The awareness of future development of additional clinical features as a consequence of the genetic diagnosis has important implications for patients with other neonatal diabetes-associated syndromes, such as IPEX syndrome, a severe multi-organ autoimmune disease caused by a mutation in FOXP3.37 Onset is usually within the first months of life, with one of the three cardinal features: severe enteropathy, eczema, or diabetes.