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Disrupted host-microbe interactions at the mucosal level are key to the pathophysiology of IBD. This study aimed to comprehensively examine crosstalk between mucosal gene expression and microbiota in patients with IBD. To study tissue-specific interactions, we perform transcriptomic (RNA-seq) and microbial (16S-rRNA-seq) profiling of 697 intestinal biopsies (645 derived from 335 patients with IBD and 52 from 16 non-IBD controls). Mucosal gene expression patterns in IBD are mainly determined by tissue location and inflammation, whereas the mucosal microbiota composition shows a high degree of individual specificity. Analysis of transcript-bacteria interactions identifies six distinct groups of inflammation-related pathways that are associated with intestinal microbiota (adjusted P < 0.05). An increased abundance of Bifidobacterium is associated with higher expression of genes involved in fatty acid metabolism, while Bacteroides correlates with increased metallothionein signaling. In patients with fibrostenosis, a transcriptional network dominated by immunoregulatory genes is associated with Lachnoclostridium bacteria in non-stenotic tissue (adjusted P < 0.05), while being absent in CD without fibrostenosis. In patients using TNF-α-antagonists, a transcriptional network dominated by fatty acid metabolism genes is linked to Ruminococcaceae (adjusted P < 0.05). Mucosal microbiota composition correlates with enrichment of intestinal epithelial cells, macrophages, and NK-cells. Overall, these data demonstrate the presence of context-specific mucosal host-microbe interactions in IBD, revealing significantly altered inflammation-associated gene-taxa modules, particularly in patients with fibrostenotic CD and patients using TNF-α-antagonists. This study provides compelling insights into host-microbe interactions that may guide microbiota-directed precision medicine and fuels the rationale for microbiota-targeted therapeutics as a strategy to alter disease course in IBD., (© 2024. The Author(s).)

Fatigue is a common and clinically challenging symptom in patients with inflammatory bowel diseases (IBD), occurring in ~ 50% of patients with quiescent disease. In this study, we aimed to investigate whether fatigue in patients with clinically quiescent IBD is reflected by circulating inflammatory proteins, which might reflect ongoing subclinical inflammation. Ninety-two (92) different inflammation-related proteins were measured in plasma of 350 patients with clinically quiescent IBD. Quiescent IBD was defined as clinical (Harvey-Bradshaw Index < 5 or Simple Clinical Colitis Activity Index < 2.5) and biochemical remission (C-reactive protein < 5 mg/L and absence of anemia) at time of fatigue assessment. Leukemia inhibitory factor receptor (LIF-R) concentrations were inversely associated with severe fatigue, also after adjustment for confounding factors (nominal P < 0.05). Although solely LIF-R showed weak ability to discriminate between mild and severe fatigue (area under the curve [AUC] = 0.61, 95%CI: 0.53-0.69, P < 0.05), a combined set of the top seven (7) fatigue-associated proteins (all P < 0.10) was observed to have reasonable discriminative performance (AUC = 0.82 [95%CI: 0.74-0.91], P < 0.01). Fatigue in patients with IBD is not clearly reflected by distinct protein signatures, suggesting there is no subclinical inflammation defined by the studied inflammatory proteins. Future studies are warranted to investigate other proteomic markers that may reflect fatigue in clinically quiescent IBD., (© 2022. The Author(s).)

Diet plays an important role in the development and progression of inflammatory bowel disease (IBD, comprising Crohn’s disease (CD) and ulcerative colitis (UC)). However, little is known about the extent to which different diets reflect inflammation in IBD beyond measures such as faecal calprotectin or C-reactive protein. In this study, we aimed to unravel associations between dietary patterns and circulating inflammatory proteins in patients with IBD. Plasma concentrations of 73 different inflammation-related proteins were measured in 454 patients with IBD by proximity extension assay (PEA) technology. Food frequency questionnaires (FFQ) were used to assess habitual diet. Principal component analysis (PCA) was performed to extract data-driven dietary patterns. To identify associations between dietary patterns and plasma proteins, we used general linear models adjusting for age, sex, BMI, plasma storage time, smoking, surgical history and medication use. Stratified analyses were performed for IBD type, disease activity and protein intake. A high-sugar diet was strongly inversely associated with fibroblast growth factor-19 (FGF-19) independent of IBD type, disease activity, surgical history and deviance from recommended protein intake (false discovery rate (FDR) < 0.05). Conversely, a Mediterranean-style pattern was associated with higher FGF-19 levels (FDR < 0.05). A pattern characterised by high alcohol and coffee intake was positively associated with CCL11 (eotaxin-1) levels and with lower levels of IL-12B (FDR < 0.05). All results were replicated in CD, whereas only the association with FGF-19 was significant in UC. Our study suggests that dietary habits influence distinct circulating inflammatory proteins implicated in IBD and supports the pro- and anti-inflammatory role of diet. Longitudinal measurements of inflammatory markers, also postprandial, are needed to further elucidate the diet−inflammation relationship.

Background and Aims: Protein profiling in patients with inflammatory bowel diseases [IBD] for diagnostic and therapeutic purposes is underexplored. This study analysed the association between phenotype, genotype, and the plasma proteome in IBD., Methods: A total of 92 inflammation-related proteins were quantified in plasma of 1028 patients with IBD (567 Crohn's disease [CD]; 461 ulcerative colitis [UC]) and 148 healthy individuals to assess protein-phenotype associations. Corresponding whole-exome sequencing and global screening array data of 919 patients with IBD were included to analyse the effect of genetics on protein levels (protein quantitative trait loci [pQTL] analysis). Intestinal mucosal RNA sequencing and faecal metagenomic data were used for complementary analyses., Results: Thirty-two proteins were differentially abundant between IBD and healthy individuals, of which 22 proteins were independent of active inflammation; 69 proteins were associated with 15 demographic and clinical factors. Fibroblast growth factor-19 levels were decreased in CD patients with ileal disease or a history of ileocecal resection. Thirteen novel cis-pQTLs were identified and 10 replicated from previous studies. One trans-pQTL of the fucosyltransferase 2 [FUT2] gene [rs602662] and two independent cis-pQTLs of C-C motif chemokine 25 [CCL25] affected plasma CCL25 levels. Intestinal gene expression data revealed an overlapping cis-expression [e]QTL-variant [rs3745387] of the CCL25 gene. The FUT2 rs602662 trans-pQTL was associated with reduced abundances of faecal butyrate-producing bacteria., Conclusions: This study shows that genotype and multiple disease phenotypes strongly associate with the plasma inflammatory proteome in IBD, and identifies disease-associated pathways that may help to improve disease management in the future., (© The Author(s) 2021. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.)

Background: Anti-tumour necrosis factor alpha (TNFα) therapy is widely used in the management of Crohn's disease (CD) and ulcerative colitis (UC). However, up to a third of patients do not respond to induction therapy and another third of patients lose response over time. To aid patient stratification, polygenetic risk scores have been identified as predictors of response to anti-TNFα therapy. We aimed to replicate the association between polygenetic risk scores and response to anti-TNFα therapy in an independent cohort of patients, to establish its clinical validity., Materials and Methods: Primary non-response, primary response, durable response and loss of response to anti-TNFα therapy was retrospectively assessed for each patient using stringent definitions. Genome wide genotyping was performed and previously described polygenetic risk scores for primary non-response and durable response were calculated. We compared polygenetic risk scores between patients with primary response and primary non-response, and between patients with durable response and loss of response, using separate analyses for CD and UC., Results: Out of 334 patients with CD, 15 (4%) patients met criteria for primary non-response, 221 (66%) for primary response, 115 (34%) for durable response and 35 (10%) for loss of response. Out of 112 patients with UC, 12 (11%) met criteria for primary non-response, 68 (61%) for primary response, 19 (17%) for durable response and 20 (18%) for loss of response. No significant differences in polygenetic risk scores were found between primary non-responders and primary responders, and between durable responders and loss of responders., Conclusions: We could not replicate the previously reported association between polygenetic risk scores and response to anti-TNFα therapy in an independent cohort of patients with CD or UC. Currently, there is insufficient evidence to use polygenetic risk scores to predict response to anti-TNFα therapy in patients with IBD., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: G.D. received an unrestricted research grant from Takeda, and received speaker fees from Pfizer and Janssen Pharmaceuticals. R.K.W. acted as consultant for Takeda, received unrestricted research grants from Takeda, Johnson and Johnson, Tramedico and Ferring and received speaker fees from MSD, Abbvie and Janssen Pharmaceuticals. E.A.M.F. received an unrestricted research grant from Takeda. The remaining authors disclose no conflicts. Our competing interests do not alter our adherence to PLOS ONE policies on sharing data and materials.

Background and Aims: Inflammatory bowel disease [IBD] phenotypes are very heterogeneous between patients, and current clinical and molecular classifications do not accurately predict the course that IBD will take over time. Genetic determinants of disease phenotypes remain largely unknown but could aid drug development and allow for personalised management. We used genetic risk scores [GRS] to disentangle the genetic contributions to IBD phenotypes., Methods: Clinical characteristics and imputed genome-wide genetic array data of patients with IBD were obtained from two independent cohorts [cohort A, n = 1097; cohort B, n = 2156]. Genetic risk scoring [GRS] was used to assess genetic aetiology shared across traits and IBD phenotypes. Significant GRS-phenotype (false-discovery rate [FDR] corrected p <0.05) associations identified in cohort A were put forward for replication in cohort B., Results: Crohn's disease [CD] GRS were associated with fibrostenotic CD [R2 = 7.4%, FDR = 0.02] and ileocaecal resection [R2 = 4.1%, FDR = 1.6E-03], and this remained significant after correcting for previously identified clinical and genetic risk factors. Ulcerative colitis [UC] GRS [R2 = 7.1%, FDR = 0.02] and primary sclerosing cholangitis [PSC] GRS [R2 = 3.6%, FDR = 0.03] were associated with colonic CD, and these two associations were largely driven by genetic variation in MHC. We also observed pleiotropy between PSC genetic risk and smoking behaviour [R2 = 1.7%, FDR = 0.04]., Conclusions: Patients with a higher genetic burden of CD are more likely to develop fibrostenotic disease and undergo ileocaecal resection, whereas colonic CD shares genetic aetiology with PSC and UC that is largely driven by variation in MHC. These results further our understanding of specific IBD phenotypes., (© The Author(s) 2020. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.)

Following publication of the original article [1], the authors.

Background: Inflammatory bowel disease (IBD) is a chronic complex disease of the gastrointestinal tract. Patients with IBD can experience a wide range of symptoms, but the pathophysiological mechanisms that cause these individual differences in clinical presentation remain largely unknown. In consequence, IBD is currently classified into subtypes using clinical characteristics. If we are to develop a more targeted treatment approach, molecular subtypes of IBD need to be discovered that can be used as new drug targets. To achieve this, we need multiple layers of molecular data generated from the same IBD patients., Construction and Content: We initiated the 1000IBD project ( https://1000ibd.org ) to prospectively follow more than 1000 IBD patients from the Northern provinces of the Netherlands. For these patients, we have collected a uniquely large number of phenotypes and generated multi-omics profiles. To date, 1215 participants have been enrolled in the project and enrolment is on-going. Phenotype data collected for these participants includes information on dietary and environmental factors, drug responses and adverse drug events. Genome information has been generated using genotyping (ImmunoChip, Global Screening Array and HumanExomeChip) and sequencing (whole exome sequencing and targeted resequencing of IBD susceptibility loci), transcriptome information generated using RNA-sequencing of intestinal biopsies and microbiome information generated using both sequencing of the 16S rRNA gene and whole genome shotgun metagenomic sequencing., Utility and Discussion: All molecular data generated within the 1000IBD project will be shared on the European Genome-Phenome Archive ( https://ega-archive.org , accession no: EGAS00001002702). The first data release, detailed in this announcement and released simultaneously with this publication, will contain basic phenotypes for 1215 participants, genotypes of 314 participants and gut microbiome data from stool samples (315 participants) and biopsies (107 participants) generated by tag sequencing the 16S gene. Future releases will comprise many more additional phenotypes and -omics data layers. 1000IBD data can be used by other researchers as a replication cohort, a dataset to test new software tools, or a dataset for applying new statistical models., Conclusions: We report on the establishment and future development of the 1000IBD project: the first comprehensive multi-omics dataset aimed at discovering IBD biomarker profiles and treatment targets.

Background: The understanding of gender differences in inflammatory bowel disease (IBD) patients is an important step towards tailored treatment for the individual patient. The aim of this study was to compare disease phenotype, clinical manifestations, disease activity, and healthcare utilization between men and women with Crohn's disease (CD) and ulcerative colitis (UC)., Methods: Two multicenter observational cohort studies with a prospective design were used to explore the differences between men and women regarding demographic and phenotypic characteristics and healthcare utilization. Detailed data on IBD-phenotype was mainly available from the Dutch IBD Biobank, while the COIN cohort provided healthcare utilization data., Results: In the Dutch IBD Biobank study, 2118 CD patients and 1269 UC patients were analyzed. Female CD patients were more often current smokers, and male UC patients were more often previous smokers. Early onset CD (<16 years) was more frequently encountered in males than in females (20% versus 12%, P < 0.01). Male CD patients were more often diagnosed with ileal disease (28% versus 20%, P < 0.01) and underwent more often small bowel and ileocecal resection. Extraintestinal manifestations (EIMs) were more often encountered in female IBD patients. In the COIN study, 1139 CD patients and 1213 UC patients were analyzed. Male CD patients used prednisone more often and suffered more often from osteopenia. IBD-specific healthcare costs did not differ between male and female IBD patients., Conclusions: Sex differences in patients with IBD include age of onset, disease location, and EIM prevalence. No large differences in therapeutic management of IBD were observed between men and women with IBD. 10.1093/ibd/izy004&#95;video1izy004&#95;Video&#95;15786481854001.

Background and Aims: Crohn's disease [CD] is a chronic inflammatory disease with unpredictable behaviour. More than half of CD patients eventually develop complications such as stenosis, for which they then require endoscopic dilatation or surgery, as no anti-fibrotic drugs are currently available. We aim to identify disease-modifying genes associated with fibrostenotic CD., Methods: We performed a within-case analysis comparing 'extreme phenotypes' using the Immunochip and replication of the top single nucleotide polymorphisms [SNPs] with Agena Bioscience in two independent case-control cohorts totalling 322 cases with fibrostenotis [recurrent after surgery] and 619 cases with purely inflammatory CD., Results: Combined meta-analysis resulted in a genome-wide significant signal for SNP rs11861007 [p = 6.0910-11], located on chromosome 16, in lncRNA RP11-679B19.1, an lncRNA of unknown function, and close to exon 9 of the WWOX gene, which codes for WW domain-containing oxidoreductase. We analysed mRNA expression of TGF-β and downstream genes in ileocecal resection material from ten patients with and without the WWOX risk allele. Patients carrying the risk allele [A] showed enhanced colonic expression of TGF-β compared to patients homozygous for the wild-type [G] allele [p = 0.0079]., Conclusion: We have identified a variant in WWOX and in lncRNA RP11-679B19.1 as a disease-modifying genetic variant associated with recurrent fibrostenotic CD and replicated this association in an independent cohort. WWOX can potentially play a crucial role in fibrostenosis in CD, being positioned at the crossroads of inflammation and fibrosis.

Objective: Patients with IBD display substantial heterogeneity in clinical characteristics. We hypothesise that individual differences in the complex interaction of the host genome and the gut microbiota can explain the onset and the heterogeneous presentation of IBD. Therefore, we performed a case-control analysis of the gut microbiota, the host genome and the clinical phenotypes of IBD., Design: Stool samples, peripheral blood and extensive phenotype data were collected from 313 patients with IBD and 582 truly healthy controls, selected from a population cohort. The gut microbiota composition was assessed by tag-sequencing the 16S rRNA gene. All participants were genotyped. We composed genetic risk scores from 11 functional genetic variants proven to be associated with IBD in genes that are directly involved in the bacterial handling in the gut: NOD2 , CARD9 , ATG16L1 , IRGM and FUT2 ., Results: Strikingly, we observed significant alterations of the gut microbiota of healthy individuals with a high genetic risk for IBD: the IBD genetic risk score was significantly associated with a decrease in the genus Roseburia in healthy controls (false discovery rate 0.017). Moreover, disease location was a major determinant of the gut microbiota: the gut microbiota of patients with colonic Crohn's disease (CD) is different from that of patients with ileal CD, with a decrease in alpha diversity associated to ileal disease (p=3.28×10 -13 )., Conclusions: We show for the first time that genetic risk variants associated with IBD influence the gut microbiota in healthy individuals. Roseburia spp are acetate-to-butyrate converters, and a decrease has already been observed in patients with IBD., Competing Interests: Competing interests: None declared., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.)

Aim: To determine the prevalence of work disability in inflammatory bowel disease (IBD), and to assess risk factors associated with work disability., Methods: For this retrospective cohort study, we retrieved clinical data from the Dutch IBD Biobank on July 2014, containing electronic patient records of 3388 IBD patients treated in the eight University Medical Centers in the Netherlands. Prevalence of work disability was assessed in 2794 IBD patients and compared with the general Dutch population. Multivariate analyses were performed for work disability (sick leave, partial and full disability) and long-term full work disability (> 80% work disability for > 2 years)., Results: Prevalence of work disability was higher in Crohn's disease (CD) (29%) and ulcerative colitis (UC) (19%) patients compared to the general Dutch population (7%). In all IBD patients, female sex, a lower education level, and extra-intestinal manifestations, were associated with work disability. In CD patients, an age > 40 years at diagnosis, disease duration > 15 years, smoking, surgical interventions, and anti-TNFα use were associated with work disability. In UC patients, an age > 55 years, and immunomodulator use were associated with work disability. In CD patients, a lower education level (OR = 1.62, 95%CI: 1.02-2.58), and in UC patients, disease complications (OR = 3.39, 95%CI: 1.09-10.58) were associated with long-term full work disability., Conclusion: The prevalence of work disability in IBD patients is higher than in the general Dutch population. Early assessment of risk factors for work disability is necessary, as work disability is substantial among IBD patients., Competing Interests: Conflict-of-interest statement: All authors have no conflict of interest related to the manuscript.

Background and Aims: The number of patients with inflammatory bowel disease [IBD], of non-Caucasian descent in Western Europe, is increasing. We aimed to explore the impact of ethnicity and country of birth on IBD phenotype., Methods: IBD patients treated in the eight University Medical Centers in The Netherlands [Dutch IBD Biobank] were divided into two groups according to their ethnicity: 1] Caucasian patients of Western and Central European descent [CEU]; and 2] patients of non-Caucasian descent [non-CEU]. The non-CEU group was subdivided according to country of birth, into: born in The Netherlands or Western Europe [non-CEU European born]; or born outside Western-Europe who migrated to The Netherlands [non-CEU non-European born]. Both comparisons were analysed for phenotype differences [by chi-square test]., Results: The Dutch IBD Biobank included 2921 CEU patients and 233 non-CEU patients. Non-CEU Crohn's disease [CD] patients more often had upper gastro-intestinal disease [16% vs 8%, p = 0.001] and anal stenosis [10% vs 4%, p = 0.002] than CEU CD patients. The use of anti-tumour necrosis factor [TNF] agents and immunomodulators was higher in non-CEU IBD patients than in CEU IBD patients [45% vs 38%, p = 0.042] and [77% vs 66%, p = 0.001], respectively. Non-CEU IBD patients born in Europe [n = 116] were diagnosed at a lower age than non-CEU IBD patients born outside Europe [n = 115] [at 22.7 vs 28.9 years old, p < 0.001]., Conclusion: Non-Caucasians had more severe disease behaviour than Caucasians. Non-CEU patients born in Europe were diagnosed at a lower age with IBD than those born outside Europe who migrated to The Netherlands., (Copyright © 2017 European Crohn’s and Colitis Organisation (ECCO). Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com)

Purpose: The Dutch IBD Biobank aims to facilitate the discovery of predictors for individual disease course and treatment response in patients with inflammatory bowel disease (IBD). In this paper, we aim to describe the establishment of the Dutch IBD Biobank, including the facilitators and barriers to establishment. Moreover, we aim to provide a complete overview of the content of the Dutch IBD Biobank., Participants: Since 2007, every patient with IBD treated in one of the eight Dutch university medical centres is asked to participate in the Dutch IBD Biobank in which 225 standardised IBD-related data items and biomaterials, such as serum, DNA, biopsies and a stool sample, are collected., Findings to Date: As of June 2014, the Dutch IBD Biobank had enrolled 3388 patients with IBD: 2118 Crohn's disease (62.5%), 1190 ulcerative colitis (35.1%), 74 IBD-unclassified (2.2%) and 6 IBD-indeterminate (0.2%). The inclusion of patients with IBD is ongoing. The quality of the biomaterials is good and serum, DNA and biopsies have been used in newly published studies., Future Plans: The genotyping (750 000 genetic variants) of all participants of the Dutch IBD Biobank is currently ongoing, enabling more genetic research. In addition, all participants will start reporting disease activity and outcome measures using an online platform and mobile app ., Competing Interests: Competing interests: FI reports personal fees for speaking from AbbVie. AAvB reports personal fees for consultation or speaking from AbbVie, Ferring, MSD, Takeda, Tramedico and VIFOR, he is member of the Committee on Drugs of the Dutch Society for Gastroenterology (NVMDL). RKW reports unrestricted research grants from Ferring and Tramedico, and personal fees during the conduct of the study from Abbott but outside the submitted work. AEvdMdJ reports unrestricted research grants from Takeda and Abbott, and personal fees during the conduct of the study from Abbott, Takeda and Tramedico outside the submitted work. NKHdB reports unrestricted research grant from FALK outside the submitted work, personal fees for consultation or speaking from AbbVie and Teva Pharma, and he is a member of the Advisory Board of MSD., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Genome-wide association studies have revealed several common genetic risk variants for ulcerative colitis (UC). However, little is known about the contribution of rare, large effect genetic variants to UC susceptibility. In this study, we performed a deep targeted re-sequencing of 122 genes in Dutch UC patients in order to investigate the contribution of rare variants to the genetic susceptibility to UC. The selection of genes consists of 111 established human UC susceptibility genes and 11 genes that lead to spontaneous colitis when knocked-out in mice. In addition, we sequenced the promoter regions of 45 genes where known variants exert cis-eQTL-effects. Targeted pooled re-sequencing was performed on DNA of 790 Dutch UC cases. The Genome of the Netherlands project provided sequence data of 500 healthy controls. After quality control and prioritization based on allele frequency and pathogenicity probability, follow-up genotyping of 171 rare variants was performed on 1021 Dutch UC cases and 1166 Dutch controls. Single-variant association and gene-based analyses identified an association of rare variants in the MUC2 gene with UC. The associated variants in the Dutch population could not be replicated in a German replication cohort (1026 UC cases, 3532 controls). In conclusion, this study has identified a putative role for MUC2 on UC susceptibility in the Dutch population and suggests a population-specific contribution of rare variants to UC.

Objectives: The aim of this study was to systematically review the rates of nonadherence to oral maintenance treatment in adolescents with inflammatory bowel disease (IBD), and to describe perceived barriers to adherence and psychosocial factors involved., Methods: The article considered studies published in MEDLINE, Embase, and PsycINFO up to March 2015. Studies that had collected data on adherence to thiopurines or aminosalicylates in a cohort of adolescents with IBD. Case reports and case series were excluded., Results: A total of 25 studies were included. Lack of uniformity of outcome measures made pooling of data impossible. Rates of medication nonadherence ranged from 2% to 93%. The most frequently reported barriers were "just forgot," "wasn't home," and "interferes with activity." Family dysfunction, peer victimization, poor health-related quality of life, poor child-coping strategies, anxiety, and depressive symptoms were associated with medication nonadherence., Conclusions: Nonadherence to oral maintenance therapy in adolescents with IBD is a significant health care problem and can lead to unnecessary escalation in therapy. Difficulties in family and social interactions, and psychosocial dysfunction can jeopardize IBD treatment outcome and should receive attention early in the course of the disease.

Background: Hidradenitis suppurativa (HS) has recently been associated with inflammatory bowel disease (IBD). The objective of this study is to investigate the prevalence of HS in IBD and to identify clinical and genetic parameters associated with HS in IBD., Methods: A questionnaire, validated for HS, was sent to 1969 patients suffering from IBD., Results: The prevalence of HS in our IBD cohort (1260 participating patients) was significantly higher than in the general population (6.8%-10.6% versus 1%-2%). IBD patients with HS were affected by IBD significantly earlier and more often treated with anti-TNF-α therapy and surgical resection compared to IBD without HS. Female gender, smoking, a higher body mass index, and younger age were independent associated parameters for HS. Within cases allelic association analysis was performed for 59 cases (IBD with HS) and 293 controls (IBD without HS). We observed 2 promising new associations in genomic regions harboring ELOVL7 (rsnumber 10057395 P = 7.15 × 10, odds ratio = 0.4), and in the intergenic region between SULT1B1 and SULT1E1 (rsnumber 2014777 P = 7.48 × 10, odds ratio = 2.3)., Conclusions: HS is present in 6.8% to 10.6% of IBD patients. Co-morbid HS is associated with an early onset of IBD in which anti-tumor necrosis factor-α therapy and surgical resections are often needed. We identified a suggestive protective association with ELOVL7 and suggestive risk association with the genes SULT1B1 and SULT1E1 for HS, in the context of IBD. These genetic associations need further exploration and replication in additional independent cohorts.

Inflammatory bowel disease (IBD), consisting of Crohn's disease and ulcerative colitis, is a chronic inflammatory disease of the gut. The etiology of IBD is complex, involving genetic as well as environmental factors. Genetic studies have identified 163 genetic risk loci for IBD, which have led to new insights into the biological mechanisms of the disease. The currently known IBD risk loci show an almost 75% overlap with genetic risk loci for other immune mediated diseases. Current studies are focused on the translation of the identified risk loci to clinical practice. The first steps towards this translation are being taken with the identification of genetic risk factors for drugs toxicity, specific disease course and response to therapy. In this review we will discuss how the IBD genetic risk loci were identified and how this knowledge can be translated towards clinical practice.

Aim: To validate the Montreal classification system for Crohn's disease (CD) and ulcerative colitis (UC) within the Netherlands., Methods: A selection of 20 de-identified medical records with an appropriate representation of the inflammatory bowel disease (IBD) sub phenotypes were scored by 30 observers with different professions (gastroenterologist specialist in IBD, gastroenterologist in training and IBD-nurses) and experience level with IBD patient care. Patients were classified according to the Montreal classification. In addition, participants were asked to score extra-intestinal manifestations (EIM) and disease severity in CD based on their clinical judgment. The inter-observer agreement was calculated by percentages of correct answers (answers identical to the "expert evaluation") and Fleiss-kappa (κ). Kappa cut-offs: < 0.4-poor; 0.41-0.6-moderate; 0.61-0.8-good; > 0.8 excellent., Results: The inter-observer agreement was excellent for diagnosis (κ = 0.96), perianal disease (κ = 0.92) and disease location in CD (κ = 0.82) and good for age of onset (κ = 0.67), upper gastrointestinal disease (κ = 0.62), disease behaviour in CD (κ = 0.79) and disease extent in UC (κ = 0.65). Disease severity in UC was scored poor (κ = 0.23). The additional items resulted in a good inter-observer agreement for EIM (κ = 0.68) and a moderate agreement for disease severity in CD (κ = 0.44). Percentages of correct answers over all Montreal items give a good reflection of the inter-observer agreement (> 80%), except for disease severity (48%-74%). IBD-nurses were significantly worse in scoring upper gastrointestinal disease in CD compared to gastroenterologists (P = 0.008) and gastroenterologists in training (P = 0.040). Observers with less than 10 years of experience were significantly better at scoring UC severity than observers with 10-20 years (P = 0.003) and more than 20 years (P = 0.003) of experience with IBD patient care. Observers with 10-20 years of experience with IBD patient care were significantly better at scoring upper gastrointestinal disease in CD than observers with less than 10 years (P = 0.007) and more than 20 years (P = 0.007) of experience with IBD patient care., Conclusion: We found a good to excellent inter-observer agreement for all Montreal items except for disease severity in UC (poor).