[APPROACH TO VERY EARLY ONSET INFLAMMATORY BOWEL DISEASE].

INTRODUCTION: Inflammatory bowel diseases (IBD) are chronic inflammatory disorders that develop in genetically susceptible subjects as a result of a dysregulated immune response to environmental triggers and microbial dysbiosis. Most cases manifest in adulthood or in adolescence. In a minority of patients, the disease manifests in the first 5-6 years of life, defined as very early-onset IBD (VEO-IBD). In some of these patients, a monogenic disorder resulting from deleterious mutations in immune-mediated or epithelial genes can be identified. Atypical manifestations, including young age at diagnosis, recurrent infections, accompanying autoimmune disorders, severe medical-refractory disease, malignancy, consanguinity and other features should prompt a detailed genetic and immune work-up. In this review, we will discuss the approach to patients with VEO-IBD and those with atypical features and review the main groups of monogenic IBD. We will also discuss the emerging use of genetic testing to facilitate these diagnoses and provide personalized care for selected patients.