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Very early onset inflammatory bowel disease (veoIBD); defined as age at presentation of less than 6 years, accounts for up to 63% of monogenic IBD. 1 Over 80 monogenic causes have been identified; encapsulating primary immune deficiencies as well as epithelial defects.2 The most recent European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) position paper on monogenic IBD recommends gene sequencing in all patients presenting at less than 2 years and any patients age 2–6 years with red flag criteria (family history, consanguinity, clinical features of immunodeficiency).3 The advent of next generation gene sequencing technologies (such as targeted panel and exome/genome sequencing) means a wider range of variants can be tested with quicker turnaround times.1 3 Genetic panels were reviewed for IBD patients diagnosed aged 6 years or younger in a single tertiary paediatric centre. The aim was to quantify the proportion of the veoIBD cohort with a monogenic diagnosis, what these diagnoses were and effects on management and prognosis.93 patients diagnosed with IBD at the age of 6 years or younger between 2010 and 2024 were identified from the departmental IBD database. Data was collected on gender, co-morbidities, family history, severity at presentation, genetic testing, management and clinical outcomes. Particular focus was then paid to any patients with pathogenic gene variants; analysing the changes made to their management and the patients’ clinical remission status.Abstract OC3 Table 1Summary of monogenic defects identified Diagnosis Number of patients Interleukin 10 deficiency 3 FMF 2 Chronic granulomatous disease 2 Cytoplasmic isoleucyl-tRNA synthetase (IARS) deficiency 1 Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) defect 1 Tumour necrosis factor alpha induced protein 3 (TNFAIP3) related disease 1 10/93 were aged under 2 years at presentation; all had genetics sent as per local guidelines. 20/83 (23%) patients aged 2 to 6 years at presentation had genetic panels sent as guided by red flag criteria and immunology review. 10/93 (10.7%) of the veoIBD cohort and 4/10 (40%) aged under 2 at diagnosis had a confirmed monogenic cause, in keeping with published rates of 0 -33% and 13–41% respectively.3 4/10 (40%) proceeded to bone marrow transplant (BMT), with 1 more planned for BMT this year. 2 patients received targeted treatment with colchicine for familial Mediterranean fever (FMF). 8/10 (80%) are currently in clinical remission and in 7/10 (70%) treatment for IBD has been discontinued.Whilst monogenic IBD remains a severe disease entity associated with significant morbidity; it often has specific and effective treatment strategies.3 Wider variant testing and quicker analysis mean these crucial diagnoses can be made earlier in presentation and therefore clinical remission can be attained in a group of patients once deemed treatment refractory.1 Rates of monogenic disease were similar in this cohort to published data. In 7/10 identification of a monogenic cause has led to targeted treatment. Genetic sequencing should be considered in all patients presenting with veoIBD, those with red flags or those refractory to standard treatment.3 References Nambu R, Warner N, Mulder DJ, et al. A systematic review of monogenic inflammatory bowel disease. Clin Gastroenterol Hepatol. 2022 Apr;20(4):e653-e663.Collen LV, Kim DY, Field M, et al. Clinical phenotypes and outcomes in monogenic versus non-monogenic very early onset inflammatory bowel disease. J Crohns Colitis. 2022 Sep 8;16(9):1380–1396.Uhlig HH, Charbit-Henrion F, Kotlarz D, et al. 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. J Pediatr Gastroenterol Nutr. 2021 Mar 1;72(3).