Diagnostic Yield of Next-generation Sequencing in Very Early-onset Inflammatory Bowel Diseases: A Multicentre Study

BACKGROUND AND AIMS

An expanding number of monogenic defects have been identified as causative of severe forms of very early-onset inflammatory bowel diseases [VEO-IBD]. The present study aimed at defining how next-generation sequencing [NGS] methods can be used to improve identification of known molecular diagnosis and to adapt treatment.

METHODS

A total of 207 children were recruited in 45 paediatric centres through an international collaborative network [ESPGHAN GENIUS working group] with a clinical presentation of severe VEO-IBD [n = 185] or an anamnesis suggestive of a monogenic disorder [n = 22]. Patients were divided at inclusion into three phenotypic subsets: predominantly small bowel inflammation, colitis with perianal lesions, and colitis only. Methods to obtain molecular diagnosis included functional tests followed by specific Sanger sequencing, custom-made targeted NGS, and in selected cases whole exome sequencing [WES] of parents-child trios. Genetic findings were validated clinically and/or functionally.

RESULTS

Molecular diagnosis was achieved in 66/207 children [32%]: 61% with small bowel inflammation, 39% with colitis and perianal lesions, and 18% with colitis only. Targeted NGS pinpointed gene mutations causative of atypical presentations, and identified large exonic copy number variations previously missed by WES.

CONCLUSIONS

Our results lead us to propose an optimised diagnostic strategy to identify known monogenic causes of severe IBD.

A toddler with recurrent oral and genital ulcers

In western countries, when a child presents with recurrent oral ulcers and colitis, the diagnosis of Crohn's disease is mostly made. In our patient, the diagnosis was Behçet's disease with gastrointestinal manifestations. Behçet's disease with gastrointestinal manifestations has a similar clinical presentation to Crohn's disease, but there is more organ involvement and the prognosis is more severe in the former. Because there is limited experience in the treatment of Behçet's disease in the paediatric population, successful and unsuccessful treatment modalities in both paediatric and adult populations should be reported.

[Ileus after the use of loperamide in a child with acute diarrhea]

A 2-year-old girl was diagnosed as having acute gastroenteritis with severe diarrhoea, for which she was prescribed a loperamide solution. Following this she developed paralytic ileus. She was then treated conservatively and was administered fluid and electrolytes parenterally. She started to recover after 48 hours. In young children with acute diarrhoea there usually is no place for medicinal treatment, and certainly not with antimotility drugs such as loperamide.

Small intestinal T cells of celiac disease patients recognize a natural pepsin fragment of gliadin

Celiac disease is a common severe intestinal disease resulting from intolerance to dietary wheat gluten and related proteins. The large majority of patients expresses the HLA-DQ2 and/or DQ8 molecules, and gluten-specific HLA-DQ-restricted T cells have been found at the site of the lesion in the gut. The nature of peptides that are recognized by such T cells, however, has been unclear so far. We now report the identification of a gliadin-derived epitope that dominantly is recognized by intestinal gluten-specific HLA-DQ8-restricted T cells. The characterization of such epitopes is a key step toward the development of strategies to interfere in mechanisms involved in the pathogenesis of celiac disease.