Ulcerative Colitis: Bitton A

Panaccione R, Fedorak RN, Aumais G, Bernard EJ, Bernstein CN, Bitton A, Croitoru K, Dieleman LA, Enns R, Feagan BG, Franchimont D, Greenberg GR, Griffiths AM, Marshall JK, Pare P, Patel S, Penner R, Render C, Seidman E, Steinhart AH. · University of Calgary, Calgary, Canada. · Can J Gastroenterol. · Pubmed #18354755 links to  free full text

Abstract: Infliximab is a chimeric, monoclonal anti-tumour necrosis factor-alpha antibody. It has been previously demonstrated to be an effective treatment for patients with Crohn's disease who do not achieve the desired response with conventional treatments. Although the etiology of ulcerative colitis (UC) differs from that of Crohn's disease, randomized controlled trials have demonstrated that infliximab is also beneficial for the treatment of moderate to severe UC in patients who are either intolerant of or refractory to immunosuppressant agents or steroids, or those who are steroid-dependent. A review of the literature is followed by practical recommendations regarding infliximab that address the needs of clinicians and UC patients. Where there is a lack of evidence-based information, the expert panel provides its combined opinion derived from the members' clinical experiences.

Bitton A. · Department of Medicine, McGill University Health Centre, Montreal, Canada. · Semin Gastrointest Dis. · Pubmed #11726080 No free full text.

Abstract: Ulcerative colitis distal to the splenic flexure includes disease confined to the rectum (proctitis), rectosigmoid (proctosigmoiditis or distal colitis), or extending to the descending colon or splenic flexure (left-sided colitis). These subtypes represent up to 60% to 80% of newly presenting cases of ulcerative colitis. Although these conditions are defined by the extent of colon that is affected, they also share the characteristic of being amenable to topical therapy. In general, the course of disease is milder and symptoms are less severe than in patients with more extensive colonic involvement. Nonetheless, symptoms may significantly impair patients' health-related quality of life. Treatment options include the oral and/or rectal 5-aminosalicylate (5-ASA) preparations. Rectal therapy delivering higher concentrations of active medication (5-ASA or glucocorticoids) directly to the inflamed mucosa while minimizing systemic absorption provides a highly effective and safe treatment. Oral glucocorticoids are indicated in patients who are resistant to or intolerant of 5-ASA therapy. Immunomodulators have an important role in individuals with glucocorticoid dependent or glucocorticoid refractory disease. This article reviews the clinical diagnosis and current medical management of ulcerative proctitis, proctosigmoiditis, and left-sided ulcerative colitis, including patients resistant to conventional medical therapy.

Bitton A, Peppercorn MA, Antonioli DA, Niles JL, Shah S, Bousvaros A, Ransil B, Wild G, Cohen A, Edwardes MD, Stevens AC. · Gastroenterology Division, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA. · Gastroenterology. · Pubmed #11208709 No free full text.

Abstract: BACKGROUND & AIMS: Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease. We aimed to assess whether clinical, biological, and histologic parameters in quiescent UC predict time to clinical relapse. METHODS: Seventy-four patients with clinically and endoscopically determined inactive UC were followed up for 1 year or for a shorter period if they had a relapse. Serum erythrocyte sedimentation rate; C-reactive protein, interleukin (IL)-1beta, IL-6, and IL-15 values; anti-neutrophil cytoplasmic antibody titers; and rectal biopsy specimens were obtained at baseline, at 6 and 12 months, and/or at relapse. Multivariate survival analysis was performed to determine independent predictors of clinical relapse. RESULTS: Twenty-seven patients relapsed (19/42 women; 8/32 men). Multivariate Cox regression analysis retained younger age (P = 0.003; hazard ratio, 0.4 per decade), greater number of prior relapses in women (P < 0.001; hazard ratio, 1.6 per prior relapse), and basal plasmacytosis (P = 0.003; hazard ratio, 4.5) on rectal biopsy specimens as predictors of shorter time to clinical relapse. Kaplan-Meier survival curves showed the 20-30-year-old age group and women with more than 5 prior relapses to be groups with shorter times to relapse. CONCLUSIONS: Younger age, multiple previous relapses (for women), and basal plasmacytosis on rectal biopsy specimens were independent predictors of earlier relapse. These findings may help identify patients with inactive UC who will require optimal maintenance medical therapy.

Shugart YY, Silverberg MS, Duerr RH, Taylor KD, Wang MH, Zarfas K, Schumm LP, Bromfield G, Steinhart AH, Griffiths AM, Kane SV, Barmada MM, Rotter JI, Mei L, Bernstein CN, Bayless TM, Langelier D, Cohen A, Bitton A, Rioux JD, Cho JH, Brant SR. · Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21231, USA. · Genes Immun. · Pubmed #18246054 No free full text.

Abstract: Inflammatory bowel disease (IBD) is a complex genetic disorder of two major phenotypes, Crohn's disease (CD) and ulcerative colitis (UC), with increased risk in Ashkenazi Jews. Twelve genome-wide linkage screens have identified multiple loci, but these screens have been of modest size and have used low-density microsatellite markers. We, therefore, performed a high-density single-nucleotide polymorphism (SNP) genome-wide linkage study of 993 IBD multiply affected pedigrees (25% Jewish ancestry) that contained 1709 IBD-affected relative pairs, including 919 CD-CD pairs and 312 UC-UC pairs. We identified a significant novel CD locus on chromosome 13p13.3 (peak logarithm of the odds (LOD) score=3.98) in all pedigrees, significant linkage evidence on chromosomes 1p35.1 (peak LOD score=3.5) and 3q29 (peak LOD score=3.19) in Jewish CD pedigrees, and suggestive loci for Jewish IBD on chromosome 10q22 (peak LOD score=2.57) and Jewish UC on chromosome 2q24 (peak LOD score=2.69). Nominal or greater linkage evidence was present for most previously designated IBD loci (IBD1-9), notably, IBD1 for CD families at chromosome 16q12.1 (peak LOD score=4.86) and IBD6 in non-Jewish UC families at chromosome 19p12 (peak LOD score=2.67). This study demonstrates the ability of high information content adequately powered SNP genome-wide linkage studies to identify loci not observed in multiple microsatellite-based studies in smaller cohorts.

De Jager PL, Franchimont D, Waliszewska A, Bitton A, Cohen A, Langelier D, Belaiche J, Vermeire S, Farwell L, Goris A, Libioulle C, Jani N, Dassopoulos T, Bromfield GP, Dubois B, Cho JH, Brant SR, Duerr RH, Yang H, Rotter JI, Silverberg MS, Steinhart AH, Daly MJ, Podolsky DK, Louis E, Hafler DA, Rioux JD, Anonymous00242, Anonymous00243. · Department of Neurology, Center for Neurologic Diseases, Brigham & Women's Hospital and Harvard Medical School, Boston, MA, USA. · Genes Immun. · Pubmed #17538633 No free full text.

Abstract: The intestinal flora has long been thought to play a role either in initiating or in exacerbating the inflammatory bowel diseases (IBD). Host defenses, such as those mediated by the Toll-like receptors (TLR), are critical to the host/pathogen interaction and have been implicated in IBD pathophysiology. To explore the association of genetic variation in TLR pathways with susceptibility to IBD, we performed a replication study and pooled analyses of the putative IBD risk alleles in NFKB1 and TLR4, and we performed a haplotype-based screen for association to IBD in the TLR genes and a selection of their adaptor and signaling molecules. Our genotyping of 1539 cases of IBD and pooled analysis of 4805 cases of IBD validates the published association of a TLR4 allele with risk of IBD (odds ratio (OR): 1.30, 95% confidence interval (CI): 1.15-1.48; P=0.00017) and Crohn's disease (OR: 1.33, 95% CI: 1.16-1.54; P=0.000035) but not ulcerative colitis. We also describe novel suggestive evidence that TIRAP (OR: 1.16, 95% CI: 1.04-1.30; P=0.007) has a modest effect on risk of IBD. Our analysis, therefore, offers additional evidence that the TLR4 pathway - in this case, TLR4 and its signaling molecule TIRAP - plays a role in susceptibility to IBD.

Dassopoulos T, Nguyen GC, Bitton A, Bromfield GP, Schumm LP, Wu Y, Elkadri A, Regueiro M, Siemanowski B, Torres EA, Gregory FJ, Kane SV, Harrell LE, Franchimont D, Achkar JP, Griffiths A, Brant SR, Rioux JD, Taylor KD, Duerr RH, Silverberg MS, Cho JH, Steinhart AH. · Johns Hopkins University Meyerhoff Inflammatory Bowel Disease Center, Baltimore MD, USA. · Inflamm Bowel Dis. · Pubmed #17427244 links to  free full text

Abstract: BACKGROUND: The NIDDK IBD Genetics Consortium (IBDGC) collects DNA and phenotypic data from inflammatory bowel disease (IBD) subjects to provide a resource for genetic studies. No previous studies have been performed on the reliability and validity of phenotypic determinations in either Crohn's disease (CD) or ulcerative colitis (UC) using primary records. Our aim was to determine the reliability and validity of these phenotypic assessments. METHODS: The de-identified records of 30 IBD patients were reviewed by 2 phenotypers per center using a standard protocol for phenotypic assessment. Each phenotyper evaluated 10 charts on 2 occasions 5 months apart. Reliability was expressed as the kappa (kappa) statistic. Performance characteristics were determined by comparison to a consensus-derived "gold standard" and by generation of receiver operating characteristic (ROC) curves. RESULTS: Agreement for diagnosis was excellent (kappa = 0.82; 95% confidence interval [CI]: 0.71-0.92). Agreement for CD location was good for jejunal, ileal, colorectal, and perianal disease with kappa between 0.60 and 0.74 but was fair for esophagogastroduodenal (kappa = 0.36). Agreement for UC extent (kappa = 0.67; 95% CI: 0.48-0.85), and CD behavior (kappa = 0.67; 95% CI: 0.49-0.83) were very good. Area under the ROC curves was greater than 0.84 for diagnosis, CD behavior, UC extent, and ileal and colonic CD location. CONCLUSIONS: IBD phenotype classification using a standard protocol exhibited very good to excellent inter- and intrarater agreement and validity. This study highlights the importance of standard protocols in generating reliable and valid phenotypic assessments. The data will facilitate estimates of phenotyping misclassification rates that should be considered when making inferences from IBD genotype-phenotype studies.

van Bodegraven AA, Curley CR, Hunt KA, Monsuur AJ, Linskens RK, Onnie CM, Crusius JB, Annese V, Latiano A, Silverberg MS, Bitton A, Fisher SA, Steinhart AH, Forbes A, Sanderson J, Prescott NJ, Strachan DP, Playford RJ, Mathew CG, Wijmenga C, Daly MJ, Rioux JD, van Heel DA. · Department of Gastroenterology, VU University Medical Centre, Amsterdam, The Netherlands. · Gastroenterology. · Pubmed #17087940 No free full text.

Abstract: BACKGROUND & AIMS: Common germline genetic variation in the 3' region of myosin IXB (MYO9B) has been associated recently with susceptibility to celiac disease, with a hypothesis that MYO9B variants might influence intestinal permeability. These findings suggested the current study investigating a possible further role for MYO9B variation in inflammatory bowel disease. METHODS: Eight single-nucleotide polymorphisms (SNPs) were selected to tag common haplotypes from the 35-kb 3' region of MYO9B. These included the strongest celiac disease-associated variants reported in a Dutch cohort. These SNPs were studied in 3 independently collected and genotyped case-control cohorts of European descent (UK, Dutch, and Canadian/Italian), comprising in total 2717 inflammatory bowel disease patients (1197 with Crohn's disease, 1520 with ulcerative colitis) and 4440 controls. RESULTS: Common variation in MYO9B was associated with susceptibility to inflammatory bowel disease in all 3 cohorts examined (most associated SNP, rs1545620; meta-analysis P = 1.9 x 10(-6); odds ratio, 1.2), with the same alleles showing association as reported for celiac disease. CONCLUSIONS: MYO9B genetic variants predispose to inflammatory bowel disease. Interestingly, rs1545620 is a nonsynonymous variant leading to an amino acid change (Ala1011Ser) in the third calmodulin binding IQ domain of MYO9B. Unlike previous variants (in other genes) reported to predispose to inflammatory bowel disease, the association at MYO9B was considerably stronger with ulcerative colitis, although weaker association with Crohn's disease also was observed. These data imply shared causal mechanisms underlying intestinal inflammatory diseases.

Duerr RH, Taylor KD, Brant SR, Rioux JD, Silverberg MS, Daly MJ, Steinhart AH, Abraham C, Regueiro M, Griffiths A, Dassopoulos T, Bitton A, Yang H, Targan S, Datta LW, Kistner EO, Schumm LP, Lee AT, Gregersen PK, Barmada MM, Rotter JI, Nicolae DL, Cho JH. · Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, School of Medicine, University of Pittsburgh, University of Pittsburgh Medical Center Presbyterian, Mezzanine Level, C-Wing, 200 Lothrop Street, Pittsburgh, PA 15213, USA. · Science. · Pubmed #17068223 links to  free full text

Abstract: The inflammatory bowel diseases Crohn's disease and ulcerative colitis are common, chronic disorders that cause abdominal pain, diarrhea, and gastrointestinal bleeding. To identify genetic factors that might contribute to these disorders, we performed a genome-wide association study. We found a highly significant association between Crohn's disease and the IL23R gene on chromosome 1p31, which encodes a subunit of the receptor for the proinflammatory cytokine interleukin-23. An uncommon coding variant (rs11209026, c.1142G>A, p.Arg381Gln) confers strong protection against Crohn's disease, and additional noncoding IL23R variants are independently associated. Replication studies confirmed IL23R associations in independent cohorts of patients with Crohn's disease or ulcerative colitis. These results and previous studies on the proinflammatory role of IL-23 prioritize this signaling pathway as a therapeutic target in inflammatory bowel disease.

Nguyen GC, Torres EA, Regueiro M, Bromfield G, Bitton A, Stempak J, Dassopoulos T, Schumm P, Gregory FJ, Griffiths AM, Hanauer SB, Hanson J, Harris ML, Kane SV, Orkwis HK, Lahaie R, Oliva-Hemker M, Pare P, Wild GE, Rioux JD, Yang H, Duerr RH, Cho JH, Steinhart AH, Brant SR, Silverberg MS. · Harvey M. and Lyn P. Meyerhoff Inflammatory Bowel Disease Center, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. · Am J Gastroenterol. · Pubmed #16696785 No free full text.

Abstract: OBJECTIVES: Inflammatory bowel disease (IBD), comprising primarily of Crohn's disease (CD) and ulcerative colitis (UC), is increasingly prevalent in racial and ethnic minorities. This study was undertaken to characterize racial differences in disease phenotype in a predominantly adult population. METHODS: Phenotype data on 830 non-Hispanic white, 127 non-Hispanic African American, and 169 Hispanic IBD patients, recruited from six academic centers, were abstracted from medical records and compiled in the NIDDK-IBD Genetics Consortium repository. We characterized racial differences in family history, disease location and behavior, surgical history, and extraintestinal manifestations (EIMs) using standardized definitions. RESULTS: African American CD patients were more likely than whites to develop esophagogastroduodenal CD (OR = 2.8; 95% CI: 1.4-5.5), colorectal disease (OR = 1.9; 95% CI: 1.1-3.4), perianal disease (OR = 1.7; 95% CI: 1.03-2.8), but less likely to have ileal involvement (OR = 0.55; 95% CI: 0.32-0.96). They were also at higher risk for uveitis (OR = 5.5; 95% CI: 2.3-13.0) and sacroiliitis (OR = 4.0; 95% CI: 1.55-10.1). Hispanics had higher prevalence of perianal CD (OR = 2.9; 95% CI: 1.8-4.6) and erythema nodosum (3.3; 95% CI: 1.7-6.4). Among UC patients, Hispanics had more proximal disease extent. Both African American and Hispanic CD patients, but not UC patients, had lower prevalences of family history of IBD than their white counterparts. CONCLUSIONS: There are racial differences in IBD family history, disease location, and EIMs that may reflect underlying genetic variations and have important implications for diagnosis and management of disease. These findings underscore the need for further studies in minority populations.

Daly MJ, Pearce AV, Farwell L, Fisher SA, Latiano A, Prescott NJ, Forbes A, Mansfield J, Sanderson J, Langelier D, Cohen A, Bitton A, Wild G, Lewis CM, Annese V, Mathew CG, Rioux JD. · The Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA, USA. · Eur J Hum Genet. · Pubmed #15841097 links to  free full text

Abstract: Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases of the gastrointestinal system known as the inflammatory bowel diseases (IBD). Recently, Stoll and colleagues reported a novel finding of genetic variation in the DLG5 gene that is associated with IBD (CD and UC combined). We present here a study of the genetic variation described in that report in two well-powered, independent case-control cohorts and one family-based collection, and confirm the proposed association between IBD and the R30Q variant of DLG5 in two of the three studies. We are, however, unable to replicate the other proposed association to the common haplotype described in Stoll et al and suggest that this other finding could conceivably have been partially a statistical fluctuation and partially a result of LD with the replicated R30Q association. This study provides support for the hypothesis that DLG5 constitutes a true IBD risk factor of modest effect.

Bitton A, Sewitch MJ, Peppercorn MA, deB Edwardes MD, Shah S, Ransil B, Locke SE. · Department of Medicine, McGill University, Montréal, Québec, Canada. · Am J Gastroenterol. · Pubmed #14572569 No free full text.

Abstract: OBJECTIVES: To determine the association between psychosocial characteristics and time to relapse in patients with inactive ulcerative colitis. METHODS: Sixty patients with clinically and endoscopically inactive ulcerative colitis were followed for 1 yr, or less if they relapsed. Demographic, psychosocial, and clinical data were obtained. Stressful life events (Psychiatric Epidemiology Research Interview Life Events Scale), psychological distress (Symptom Checklist-90R), and perceived stress (Perceived Stress Scale) were recorded monthly by self-report. Multivariate time-dependent Cox regression was used to identify the independent determinants of earlier time to clinical relapse. RESULTS: The patients' mean age was 39 yr (SD = 9.4), 37 (62%) were female, and 22 (37%) relapsed during the 1-yr follow-up. Univariate Cox regression indicated a weak association between number of stressful events in the preceding month and time to relapse (p = 0.09). This association strengthened in multivariate analysis (p = 0.02, hazard ratio = 1.26 per event, 95% CI = 1.04-1.53) after adjustment for significant covariates. CONCLUSIONS: After controlling for demographic and clinical variables, more recent stressful events were associated with earlier time to relapse. These findings, which support a biopsychosocial model of disease, might help clinicians identify patients who might benefit from more intensive maintenance medical therapy and behavioral medicine interventions to reduce stress and improve coping.

Sewitch MJ, Abrahamowicz M, Barkun A, Bitton A, Wild GE, Cohen A, Dobkin PL. · Groupe de Recherche Interdisciplinaire en Santé, University of Montreal, Montreal, Quebec, Canada. · Am J Gastroenterol. · Pubmed #12873575 No free full text.

Abstract: OBJECTIVE: The aim of this study was to identify determinants of nonadherence to medication in outpatients with established inflammatory bowel disease (IBD). METHODS: Ten gastroenterologists and 153 of their IBD patients participated in this prospective study. Demographic, clinical, and psychosocial characteristics, as well as patient-physician discordance, were assessed at an office visit. Nonadherence to medication was assessed 2 wk later. Separate generalized estimating equations were used to identify determinants of nonadherence. RESULTS: Physicians averaged 47.9 yr in age (range 30.1-57.5 yr), and 90% were male. Patients averaged 37.0 yr (SD = 15.1), and 87 (56.9%) were female. In all, 63 patients (41.2%) were nonadherent to medication; of these, 51 (81.0%) indicated unintentional nonadherence, 23 (36.5%) intentional nonadherence, and 11 (17.5%) both. Overall nonadherence was predicted by disease activity (OR = 0.55, p = 0.0022), new patient status (OR = 2.14, p = 0.0394), disease duration (OR = 0.50, p = 0.0001), and scheduling a follow-up appointment (OR = 0.30, p = 0.0059), whereas higher discordance on well-being was predictive only in psychologically nondistressed patients (p = 0.0026 for interaction). Unintentional nonadherence was predicted by age (OR = 0.97, p = 0.0072), new patient status (OR = 2.80, p = 0239), and higher discordance on well-being in psychologically nondistressed patients (p = 0.0504). Intentional nonadherence was predicted by disease duration (OR = 0.55, p = 0032), scheduling a follow-up appointment (OR = 0.12, p = 0.0001), certainty that medication would be helpful (OR = 0.99, p = 0.0409), and total patient-physician discordance (OR = 1.59, p =.0120). CONCLUSIONS: These findings suggest that the therapeutic relationship, as well as individual clinical and psychosocial characteristics, influence adherence to medication.

Aumais G, Lefebvre M, Tremblay C, Bitton A, Martin F, Giard A, Madi M, Spénard J. · Algorithme Pharma Inc., Montréal, Quebec, Canada. · Aliment Pharmacol Ther. · Pubmed #12492737 links to  free full text

Abstract: OBJECTIVE: Patients with ulcerative proctitis may have rectal mucosal properties different from healthy volunteers. This project compared the pharmacokinetics of rectally administered mesalazine in these two populations. METHODS: In two separate studies, nine patients with ulcerative proctitis and 16 healthy volunteers received a single 500 mg mesalazine suppository and then 500 mg every 8 h for 5 days. Blood samples were collected for 12 h in healthy volunteers and 30 h in patients, and urine for 24 h in healthy volunteers and 30 h in patients. Rectal biopsies were performed 8 h after the last dose. RESULTS: After a single dose to patients, mean mesalazine half-life (s.d.) was 5.0 (3.6) h. At steady-state, means (s.d.) were 89.1 (78.9) ng/mL for C(min), 361.1 (240.8) ng/mL for C(max), and 7.1 (7.3) h for half-life. Mean (range) rectal mesalazine concentrations were 167 (1.4-541.6) ng/mg tissue. After a single dose in healthy volunteers, mean (s.d.) half-life was 4.0 (4.7) h. At steady-state, means (s.d.) were 22.4 (61.6) ng/mL for C(min), 359.4 (166.3) ng/mL for C(max), and 0.9 (0.5) h for half-life. CONCLUSION: Mesalazine is released in the rectum of patients, with a bioavailability of about 40%. Tissue distribution is also appreciable. Both parameters appear higher than in healthy volunteers.

Sewitch MJ, Abrahamowicz M, Bitton A, Daly D, Wild GE, Cohen A, Katz S, Szego PL, Dobkin PL. · Division of Clinical Epidemiology, Montréal General Hospital, Québec, Canada. · Am J Gastroenterol. · Pubmed #12358229 No free full text.

Abstract: OBJECTIVE: The aim of this study was to identify the independent psychosocial correlates of patient-physician discordance in adult outpatients with inflammatory bowel disease. METHODS: This cross-sectional study was conducted in three university-affiliated tertiary care settings. Psychological distress, social support, perceived stress, and negative life events were assessed, as were demographic, lifestyle, and clinical characteristics. Patient-physician discordance was assessed with 10-item questionnaires. RESULTS: Ten gastroenterologists and 200 of their patients participated. Patients and their physicians disagreed most on discussion of personal issues. Patients with Crohn's disease had statistically significantly higher discordance on disease activity and physical limitation, as well as higher average overall discordance scores than patients with ulcerative colitis. Mean discordance levels were similar across different physicians. Higher psychological distress and more perceived stress were independently associated with higher discordance after controlling for Crohn's disease, active disease, being with the treating physician for less than 1 yr, and recommendation for further medical investigation. Psychological distress was the most important correlate of overall discordance. CONCLUSIONS: Increased physician awareness that psychologically distressed patients have difficulty processing of clinically relevant information may lead to improved doctor-patient communication during an office visit.

Rioux JD, Silverberg MS, Daly MJ, Steinhart AH, McLeod RS, Griffiths AM, Green T, Brettin TS, Stone V, Bull SB, Bitton A, Williams CN, Greenberg GR, Cohen Z, Lander ES, Hudson TJ, Siminovitch KA. · Whitehead Institute/Massachusetts Institute of Technology, Center for Genome Research, Cambridge, MA 02139, USA. · Am J Hum Genet. · Pubmed #10777714 links to  free full text

Abstract: The chronic inflammatory bowel diseases (IBDs)-Crohn disease (CD) and ulcerative colitis (UC)-are idiopathic, inflammatory disorders of the gastrointestinal tract. These conditions have a peak incidence in early adulthood and a combined prevalence of approximately 100-200/100,000. Although the etiology of IBD is multifactorial, a significant genetic contribution to disease susceptibility is implied by epidemiological data revealing a sibling risk of approximately 35-fold for CD and approximately 15-fold for UC. To elucidate the genetic basis for these disorders, we undertook a genomewide scan in 158 Canadian sib-pair families and identified three regions of suggestive linkage (3p, 5q31-33, and 6p) and one region of significant linkage to 19p13 (LOD score 4.6). Higher-density mapping in the 5q31-q33 region revealed a locus of genomewide significance (LOD score 3.9) that contributes to CD susceptibility in families with early-onset disease. Both of these genomic regions contain numerous genes that are important to the immune and inflammatory systems and that provide good targets for future candidate-gene studies.