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Isolated colonic (L2) Crohn’s disease (CD) in adults is thought to have unique clinical and genetic features compared with ileal (L1) CD and ulcerative colitis (UC). Similar studies in paediatrics are scarce. Our goal was to characterize the clinical features of paediatric patients with isolated colonic CD and compare them to patients with ileo-cecal CD and those with UC.

This was a multi-center retrospective study including 21 sites affiliated with the Porto IBD group and IBD interest group of ESPGHAN. Data of paediatric patients diagnosed between 2014-2017 with L1 or L2 CD, or with UC, was collected, including information on demographic, clinical and laboratory parameters at diagnosis, end of induction, 1 year and 3 years after diagnosis (or at last follow-up).

Data was collected on 300 children (102 L1, 94 L2, 104 UC) with similar demographic features. At diagnosis, bloody stools were identified in 45% of L2 patients, compared with 15% and 95% of L1 and UC patients, respectively (P<0.001), while fever was documented in 27% of L2 patients, compared to 13% and 3% of L1 and UC patients, respectively (P<0.001). At the time of diagnosis, the median pediatric Crohn’s disease activity index for patients with L1 and L2 was 25 (IQR 17.5-37) and 27.5 (20-40), respectively, while the median pediatric ulcerative colitis activity index was 40 (30-55) for patients with UC. C-reactive protein levels were significantly higher among CD patients (both L1 and L2), compared to patients with UC, and calprotectin values were comparable. ASCA was positive in 55%, 25% and 2% (P<0.001) and pANCA in 2%, 17% and 53% (P<0.001) in L1, L2 and UC patients, respectively. Granulomas were identified in 36% of L2 patients, similar to patients with L1 (33%). For induction therapy, exclusive enteral nutrition, oral steroids and mesalazine were used in 50%, 45% and 38% of patients with L2 CD, compared with 72%, 28% and 9%, and 0%, 52% and 75% of L1 and UC patients, respectively (P<0.001). Steroid-free clinical remission at the end of induction was overall similar between groups, around 55%. At 1-year post-diagnosis, 62%, 68% and 40% were on an immunomodulator (P=0.03) and 41%, 26% and 22% were receiving anti-TNFα agent (P=0.01), of patients with L1, L2 and UC, respectively. While time to initiation of an anti-TNFα agent was significantly shorter in L1 patients compared with L2 and UC (P=0.03), time to admission and time to surgery were similar.

Paediatric patients with isolated colonic CD exhibit several clinical features which differentiate them from ileo-cecal CD and UC. Prospective studies are required to understand the pathogenesis of this unique entity and define short- and long-term outcomes.

Patients with Crohn’s disease (CD) can develop complications including stricturing and penetrating disease [1, 2]. Although reliable baseline predictors of disease progression are urgently needed to inform management strategies, few studies have comprehensively explored the phenotypic and genetic determinants of disease progression in a sufficiently powered cohort.

We used data from 13,926 patients with CD in the UK IBD BioResource to investigate the effects of clinical phenotypes and genetics on CD progression. Median follow-up was 10.6 years and total follow-up was 193,033 patient-years. We applied the Montreal classification system to define disease as B1 (inflammatory), B2 (stricturing) and B3 (penetrating). Patients with B2 or B3 disease (N = 5,185) were compared to patients with B1 disease (N = 8,471) in a multivariate model fitted with both phenotype data and a polygenic score that we developed. Associations with q-values (false discovery rate adjusted p-values) less than 0.05 were defined as statistically significant.

CD progression occurred over time from diagnosis (Figure 1). Consistent with previous findings, we confirmed factors including smoking, disease location and perianal disease were associated with disease progression [3] (Table 1). The impact of a genetic influence on disease progression was confirmed and shown to be independent of genetic effects on disease location [4]. Early prescription of medications showed a protective effect on disease progression: Infliximab, adalimumab and thiopurines significantly reduced the chance of B2/B3 progression when prescribed within two years of diagnosis. Additionally, we observed a decreased progression to B2/B3 disease in patients diagnosed recently (between 2012-2020) compared to those diagnosed before 2012. This finding persisted after conditioning on exposure to biologics and correcting for follow-up time and interval to first thiopurine prescription, and thus may be indicative of other improvements in standards of care in recent years.

Using a large, well-characterised cohort we confirm the importance of disease location, smoking status and genetics on disease progression. We highlight the positive impact of early medication prescription on disease progression and discover an independent signal relating to potential improvements in the standard of care in CD over time. These results create the framework for reliable predictors of CD progression that may better guide future CD management strategies.

Reference:
1. Cosnes, J., et al., Inflamm Bowel Dis, 2002. 8(4): 244-50
2. Lo, B., et al.,J Crohns Colitis, 2018. 12(3): 265-272
3. Torres, J., et al., J Crohns Colitis, 2016. 10(12): 1385-1394
4. Cleynen, I., et al., Lancet, 2016. 387(10014): 156-67