Patients with a diverse spectrum of rare genetic disorders can present with inflammatory bowel diseases (monogenic IBD). Patients with these disorders often develop symptoms during infancy or early childhood, along with endoscopic or histologic features of Crohn’s disease, ulcerative colitis or IBD unclassified. Defects in interleukin 10 signaling have a Mendelian inheritance pattern with complete penetrance of intestinal inflammation. Several genetic defects that disturb intestinal epithelial barrier function or affect innate and adaptive immune function have incomplete penetrance of the IBD-like phenotype. Several of these monogenic conditions do not respond to conventional therapy and are associated with high morbidity and mortality. Due to the broad spectrum of these extremely rare diseases, a correct diagnosis is frequently a challenge and often delayed. In many cases, these diseases cannot be categorized based on standard histologic and immunologic features of IBD. Genetic analysis is required to identify the cause of the disorder and offer the patient appropriate treatment options, which include medical therapy, surgery, or allogeneic hematopoietic stem cell transplantation. In addition, diagnosis based on genetic analysis can lead to genetic counseling for family members of patients. We describe key intestinal, extra-intestinal, and laboratory features of 50 genetic variants associated with IBD-like intestinal inflammation. We provide approaches for identifying patients likely to have these disorders. We discuss classical approaches to identify these variants in patients, starting with phenotypic and functional assessments that lead to analysis of candidate genes. As a complementary approach, we discuss parallel genetic screening using next-generation sequencing followed by functional confirmation of genetic defects.

Background & Aims Very early onset inflammatory bowel diseases (VEOIBD), including infant disorders, are a diverse group of diseases found in children less than 6 years of age. They have been associated with several gene variants. We aimed to identify genes that cause VEOIBD. Methods We performed whole-exome sequencing of DNA from 1 infants with severe enterocolitis and her parents. Candidate gene mutations were validated in 40 pediatric patients and functional studies were carried out using intestinal samples and human intestinal cell lines. Results We identified compound heterozygote mutations in the tetratricopeptide repeat domain 7 (TTC7A) gene in an infant from non-consanguineous parents with severe exfoliative apoptotic enterocolitis; we also detected the mutations in 2 unrelated families, each with 2 affected siblings. TTC7A interacts with EFR3 homolog B (EFR3B) to regulate phosphatidylinositol 4-kinase (PI4KA) at the plasma membrane. Functional studies demonstrated that TTC7A is expressed in human enterocytes. The mutations we identified in TTC7A result in either mislocalization or reduced expression of TTC7A. PI4KA was found to co-immunoprecipitate with TTC7A; the identified TTC7A mutations reduced this binding. Knockdown of TTC7A in human intestinal-like cell lines reduced their adhesion, increased apoptosis, and decreased production of phosphatidylinositol 4-phosphate. Conclusion In a genetic analysis, we identified loss of function mutations in TTC7A in 5 infants with VEOIBD. Functional studies demonstrated that the mutations cause defects in enterocytes and T cells that lead to severe apoptotic enterocolitis. Defects in the PI4KA–TTC7A–EFR3B pathway are involved in the pathogenesis of VEOIBD.

Institutions on behalf of the World Organisation of Digestive Endoscopy (OMED) and the European Crohn's and Colitis Organisation (ECCO)

SARS-CoV-2 has caused a global health crisis and mass vaccination programmes provide the best opportunity for controlling transmission and protecting populations. Despite the impressive clinical trial results of the BNT162b2 (Pfizer/BioNTech), ChAdOx1 nCoV-19 (Oxford/AstraZeneca), and mRNA-1273 (Moderna) vaccines, important unanswered questions remain, especially in patients with pre-existing conditions. In this position statement endorsed by the British Society of Gastroenterology Inflammatory Bowel Disease (IBD) section and IBD Clinical Research Group, we consider SARS-CoV-2 vaccination strategy in patients with IBD. The risks of SARS-CoV-2 vaccination are anticipated to be very low, and we strongly support SARS-CoV-2 vaccination in patients with IBD.Based on data from previous studies with other vaccines, there are conceptual concerns that protective immune responses to SARS-CoV-2 vaccination may be diminished in some patients with IBD, such as those taking anti-TNF drugs. However, the benefits of vaccination, even in patients treated with anti-TNF drugs, are likely to outweigh these theoretical concerns. Key areas for further research are discussed, including vaccine hesitancy and its effect in the IBD community, the effect of immunosuppression on vaccine efficacy, and the search for predictive biomarkers of vaccine success.

IBD in children with disease onset before the age of 2 years is frequently unclassifiable into Crohn's disease and ulcerative colitis, particularly treatment resistant, and can be indistinguishable from monogenic diseases with IBD-like phenotype.

Excluding or confirming known VEOIBD genotypes should be considered early in the disease course in all cases of therapy-refractory VEOIBD, as it can have a direct impact on patient management. To combine both described NGS technologies would compensate for the limitations of WES for disease-specific application while offering the opportunity for novel gene discovery in the research setting.

Inflammatory bowel disease (IBD) is a chronic inflammatory disease characterized by abdominal pain, bloody diarrhoea, and malabsorption leading to weight loss. It is considered the result of inadequate control of an excessive reaction of the immune system to the resident flora of the gut. Like other primary immunodeficiencies, IL-10 and IL-10 receptor (IL10R) deficiency present with IBD and demonstrate the sensitivity of the intestine to any changes of the immune system. Both IL-10 and IL10R deficiency cause severe early-onset enterocolitis and can be successfully treated by hematopoietic stem cell transplantation (HSCT).

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