Inflammatory bowel diseases (IBD), categorized as ulcerative colitis (UC), Crohn's disease (CD), or IBD-undetermined (IBDU), are increasing in incidence. IBD is understood to result from environmental factors interacting with a pre-existing genetic susceptibility. Approximately 1% of all patients with inflammatory bowel disease (IBD) are diagnosed before the age of 6 years, designated as very-early-onset IBD (VEOIBD). This cohort of patients is distinguished from other age groups by differences in disease phenotype and by a higher burden of genetic mutations. Recent studies have linked mutations in NADPH oxidase function to VEOIBD and even pediatric IBD. Loss-of-function NOX2 variants expressed in phagocytes and NOX1/DUOX2 variants expressed in intestinal epithelial cells have been associated with VEOIBD and pediatric and adult IBD in patients. Cell and animal studies suggest a protective role for these reactive oxygen species (ROS)-producing enzymes in intestinal homeostasis-a paradigm that challenges the conventional concept that only increased ROS result in cell and tissue damage. Examining the role of NADPH oxidases in VEOIBD may improve our understanding of the pathophysiology of this disease and will uncover new therapeutic possibilities.
Keywords: DUOX; Inflammatory bowel disease; Intestine; NADPH oxidase; NOX; Reactive oxygen species; VEOIBD.