Infliximab therapy for inflammatory colitis in an infant with NEMO deficiency

Breaking Down Barriers: Epithelial Contributors to Monogenic IBD Pathogenesis

Monogenic causes of inflammatory bowel diseases (IBD) are increasingly being discovered. To date, much attention has been placed in those resulting from inborn errors of immunity. Therapeutic efforts have been largely focused on offering personalized immune modulation or curative bone marrow transplant for patients with IBD and underlying immune disorders. To date, less emphasis has been placed on monogenic causes of IBD that pertain to impairment of the intestinal epithelial barrier. Here, we provide a comprehensive review of monogenic causes of IBD that result in impaired intestinal epithelial barrier that are categorized into 6 important functions: (1) epithelial cell organization, (2) epithelial cell intrinsic functions, (3) epithelial cell apoptosis and necroptosis, (4) complement activation, (5) epithelial cell signaling, and (6) control of RNA degradation products. We illustrate how impairment of any of these categories can result in IBD. This work reviews the current understanding of the genes involved in maintaining the intestinal barrier, the inheritance patterns that result in dysfunction, features of IBD resulting from these disorders, and pertinent translational work in this field.

Understanding very early onset inflammatory bowel disease (VEOIBD) in relation to inborn errors of immunity

Inflammatory bowel diseases (IBD) are multifactorial diseases which are caused by the combination of genetic predisposition, exposure factors (environmental and dietary), immune status, and dysbiosis. IBD is a disease which presents at any age, ranging from newborns to the elderly. The youngest of the pediatric IBD population have a more unique presentation and clinical course and may have a different etiology. Very early onset IBD (VEOIBD) patients, designated as those diagnosed prior the age of 6, have distinct features which are more frequent in this patient population including increased incidence of monogenetic causes for IBD (0%-33% depending on the study). This proportion is increased in the youngest subsets, which is diagnosed prior to the age of 2. To date, there are approximately 80 monogenic causes of VEOIBD that have been identified and published. Many of these monogenic causes are inborn errors of immunity yet the majority of VEOIBD patients do not have an identifiable genetic cause for their disease. In this review, we will focus on the clinical presentation, evaluation, and monogenic categories which have been associated with VEOIBD including (1) Epithelial cell defects (2) Adaptive immune defects, (3) Innate Immune/Bacterial Clearance and Recognition defects, and (4) Hyperinflammatory and autoinflammatory disorders. We will highlight differential diagnosis of VEOIBD presentations, as well as evaluation and treatment, which will be helpful for those who study and care for VEOIBD patients outside of the pediatric gastroenterology field. This is a fast-moving field of research which has grown significantly based on knowledge that we gain from our patients. These scientific findings have identified novel mucosal biology pathways and will continue to inform our understanding of gastrointestinal biology.

Clinical Genomics for the Diagnosis of Monogenic Forms of Inflammatory Bowel Disease: A Position Paper From the Paediatric IBD Porto Group of European Society of Paediatric Gastroenterology, Hepatology and Nutrition

BACKGROUND

It is important to identify patients with monogenic IBD as management may differ from classical IBD. In this position statement we formulate recommendations for the use of genomics in evaluating potential monogenic causes of IBD across age groups.

METHODS

The consensus included paediatric IBD specialists from the Paediatric IBD Porto group of the European Society of Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) and specialists from several monogenic IBD research consortia. We defined key topics and performed a systematic literature review to cover indications, technologies (targeted panel, exome and genome sequencing), gene panel setup, cost-effectiveness of genetic screening, and requirements for the clinical care setting. We developed recommendations that were voted upon by all authors and Porto group members (32 voting specialists).

RESULTS

We recommend next-generation DNA-sequencing technologies to diagnose monogenic causes of IBD in routine clinical practice embedded in a setting of multidisciplinary patient care. Routine genetic screening is not recommended for all IBD patients. Genetic testing should be considered depending on age of IBD-onset (infantile IBD, very early-onset IBD, paediatric or young adult IBD), and further criteria, such as family history, relevant comorbidities, and extraintestinal manifestations. Genetic testing is also recommended in advance of hematopoietic stem cell transplantation. We developed a diagnostic algorithm that includes a gene panel of 75 monogenic IBD genes. Considerations are provided also for low resource countries.

CONCLUSIONS

Genomic technologies should be considered an integral part of patient care to investigate patients at risk for monogenic forms of IBD.

Receptor-interacting protein kinase 1 (RIPK1) as a therapeutic target

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a key mediator of cell death and inflammation. The unique hydrophobic pocket in the allosteric regulatory domain of RIPK1 has enabled the development of highly selective small-molecule inhibitors of its kinase activity, which have demonstrated safety in preclinical models and clinical trials. Potential applications of these RIPK1 inhibitors for the treatment of monogenic and polygenic autoimmune, inflammatory, neurodegenerative, ischaemic and acute conditions, such as sepsis, are emerging. This article reviews RIPK1 biology and disease-associated mutations in RIPK1 signalling pathways, highlighting clinical trials of RIPK1 inhibitors and potential strategies to mitigate development challenges.

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) — a key mediator of cell death and inflammation — is activated in human diseases. Here, Yuan and colleagues discuss current understanding of RIPK1 biology and its association with diseases including inflammatory and autoimmune disorders, neurodegenerative diseases and sepsis. The clinical development of small-molecule RIPK1 inhibitors and associated challenges are discussed.