Beyond IBD: the genetics of other early-onset diarrhoeal disorders.

Diarrhoeal disorders in childhood extend beyond the inflammatory bowel diseases. Persistent and severe forms of diarrhoea can occur from birth and are associated with significant morbidity and mortality. These disorders can affect not only the gastrointestinal tract but frequently have extraintestinal manifestations, immunodeficiencies and endocrinopathies. Genomic analysis has advanced our understanding of these conditions and has revealed precision-based treatment options such as potentially curative haematopoietic stem cell transplant. Although many new mutations have been discovered, there is frequently no clear genotype-phenotype correlation. The functional effects of gene mutations can be studied in model systems such as patient-derived organoids. This allows us to further characterise these disorders and advance our understanding of the pathophysiology of the intestinal mucosa. In this review, we will provide an up to date overview of genes involved in diarrhoeal disorders of early onset, particularly focussing on the more recently described gene defects associated with protein loosing enteropathy.

Mucosal Atrophy Predicts Poorer Outcomes in Pediatric Ulcerative Colitis-A National Inception Cohort Study.

BACKGROUND: Outcomes in pediatric ulcerative colitis (UC) are heterogeneous and predictors of disease course eagerly sought. Mucosal atrophy (MA) is characterized by histological abnormalities of colonic intestinal glands. OBJECTIVE: To determine the prevalence of MA in a national inception cohort of pediatric UC and its impact on outcomes. METHODS: Irish children < 16 years old with UC are diagnosed at a single referral center. At diagnosis, patients underwent phenotyping by Paris classification and activity assessment by Pediatric Ulcerative Colitis Activity Index. Biopsies from all colonic segments were evaluated for MA. Patients were followed prospectively. The primary outcome was corticosteroid-free remission at 1 year. Secondary outcomes included relapse, treatment escalation, and colectomy by 2 years. RESULTS: Of 251 pediatric patients with UC (mean age 11.8 years, 55% male), 38 (15%) had MA on diagnostic biopsy. Baseline characteristics were similar between groups with/without MA and there was no difference in steroid-free remission or rates of moderate-severe UC at 1 year. Patients with MA had higher use of steroids (29% vs 15%, P = 0.04) and immunomodulators (40% vs 21%, P = 0.04) at 6 months, higher biologic use at 1 year (34% vs 16%, P = 0.03), earlier first relapse (mean ± SD 29.4 ± 26.1 vs 46.7 ± 43.4 weeks after diagnosis, P = 0.02), and higher colectomy rates by 2 years (21% vs 8%, P = 0.01). CONCLUSIONS: Children with MA at diagnosis had higher colectomy rates despite earlier treatment escalation and similar baseline severity scores. We identify MA as a promising new prognostic marker in children with newly diagnosed UC.

Body Surface Area-Based Dosing of Infliximab is Superior to Standard Weight-Based Dosing in Children With Very Early Onset Inflammatory Bowel Disease.

Background and Aims: Children with very early onset inflammatory bowel disease (VEO-IBD) are uniquely at risk of inadequate infliximab (IFX) exposure. We studied the association between standard body weight (BW)-based and body surface area (BSA)-based dosing strategies and outcomes. Methods: We identified VEO-IBD patients treated with IFX before 9 years at a single center. Patients were separated into those that received a BSA-based dose (200 mg/m2) and standard BW dosing (5 mg/kg). IFX drug levels, dose intensification, time on steroids, and long-term outcomes were compared. Receiver operator characteristic curves determined the optimal BW- and BSA-based dose to achieve a trough ≥10 µg/ml at dose 4 (IFX#4). Results: Forty-three children with VEO-IBD were identified. Receiver operator characteristic curves demonstrated optimal BW- and BSA-based doses to achieve IFX trough ≥10 µg/ml at IFX#4 were 7.5 mg/kg and 180mg/m2. Children were classified to standard BW dosing (22/43) and BSA dosing (10/43). IFX#4 trough was significantly higher in those who received BSA dosing (BSA 18.6 µg/ml [interquartile range 10.8-28.1] vs BW 5.1 µg/ml [interquartile range 2.6-10.7], P = .04). BSA dosing was more likely to achieve a target drug level >10 µg/ml at IFX#4 (BSA 70% vs BW 18%, P = .02). BW dosing was associated with a greater likelihood of dose escalation (BW 82% vs BSA 30%, P < .01) and a shorter time to first escalation. BSA dosing was associated with shorter time spent on steroids (P = .02). Conclusion: Young children require higher IFX dosing to achieve adequate drug exposure. Our data support the use of a BSA-based dose of 200 mg/m2 or, if a BW-based approach is used, 7.5 mg/kg. BSA dosing allows the use of a consistent dose over the age and weight spectrum.

Endoscopic and Histologic Predictors of Outcomes in Pediatric Ulcerative Colitis-Caveat Emptor.

The impact of endoscopic and histological mucosal healing on outcomes in adult settings is impressive. Despite many clinical parallels, pediatric ulcerative colitis (UC) is set apart from adult disease in several respects. Many frequently used indices are not fully validated, especially in pediatric settings, and consensus on precise definitions in clinical settings are lacking. Endoscopic mucosal healing is an acceptable long-term treatment goal in pediatrics, but not histologic normalization. Early prediction of disease course in UC may allow treatment stratification of patients according to risks of relapse, acute severe colitis, and colectomy. Putative endoscopic and histologic predictors of poor clinical outcomes in adults have not held true in pediatric settings, including baseline endoscopic extent, endoscopic severity, and specific histologic characteristics which are less prevalent in pediatrics at diagnosis. In this mini-review we appraise predictive endoscopic and histologic factors in pediatric UC with reference to relapse, severe colitis, and colectomy risks. We recommend that clinicians routinely use endoscopic and histologic sores to improve the quality of clinical and research practice. The review summarizes differences between adult and pediatric prediction data, advises special consideration of those with primary sclerosing cholangitis, and suggests areas for future study in this field.