Increasing evidence suggests that SD can mimic inflammatory bowel disease (IBD) and that it is associated with PIDs patients who have defective IL-12/2310–16 and IL-10 signalling17–21, profound T cell defects22–29, nicotinamide adenine dinucleotide phosphate oxidase anomalies30, 31, anti-apoptosis signalling of X-linked inhibitor of apoptosis (XIAP)32–35, and nuclear factor kappa B transcription (NEMO) signalling36. This evidence concerns the gene IKBKG and inflammatory bowel disease.