IPEX syndrome - Patients develop intractable chronic diarrhea secondary to autoimmune small bowel inflammation (the colon can also be affected). Additional key features of this disease include endocrinopathies (type I diabetes and thyroid disease), atopic dermatitis and autoimmune cytopenias.
IPEX is caused by mutations in the FOXP3 gene. Foxp3 is a master transcription factor responsible for the development and function of T regulatory cells (Tregs). Tregs function to suppress peripheral autoreactive T cells through a contact-dependent and cytokine-mediated mechanism. Treg dysfunction leads to loss of peripheral tolerance and activation of self-reactive lymphocytes which cause autoimmune disease.