Background This study aimed to understand the disease characteristics and treatment outcomes of Crohn’s disease (CD) in a real-world setting in China. Methods In this prospective, non-interventional, multicenter disease registry, adults (≥18 years) with existing and newly diagnosed CD were recruited from 14 medical centers across China from January 2015 to January 2017. The study consisted of the enrollment and follow-up periods, of 12 months each. Demographic, clinical characteristics, diagnostic duration and management of CD at enrollment were evaluated. Logistic regression analysis and stepwise multivariate logistic regression analysis used to assess the relationship between the risk factors and CD. Results Of 504 enrolled patients, 499 (99.0%) were eligible for analysis. The mean (SD) age at study enrollment was 32.3 (11.43) years and the majority (69.7%) of participants were male. In the past 15 years, a sustained decrease of the period of time in the diagnosis of CD was observed, at about 39.4 (24.11) months in 2010, which decreased to 3.1 (2.13) months in 2015. The most common presenting symptoms of CD included abdominal pain (78.0%), diarrhea (58.1%), weight loss (52.9%) and fever (30.1%). Oral ulcer (19.4%) and arthritis (9.8%) were the most common extra-intestinal manifestations. Non-stricturing non-penetrating (B1) (49.9%) behavior and ileocolonic involvement (L3) (56.2%) location were more frequent. Perianal disease was observed in 29.1% of the patients. Around 23.8% (119/499) patients had CD-related surgery other than perianal disease surgery. Older age at enrollment, longer disease course, complicated disease behavior and absence of perianal disease were all surgery risk factors ( p < 0.05). The most common medications was immunomodulators (e.g., azathioprine) (41.5%), anti-TNFα agents (32.9%) and aminosalicylates (20.6%). The mean (SD) Crohn’s Disease Active Index (CDAI) score was 159.1 (91.45) and almost half of the patients (49.1%, 81/165) were in remission. Conclusions This study demonstrated the CD-disease characteristics, risk factors of CD-related surgery and perianal disease, and treatment strategies in a real-world setting in China and may help in developing programs to diagnose and manage patients with CD. Electronic supplementary material The online version of this article (10.1186/s12876-019-1057-2) contains supplementary material, which is available to authorized users.

Inflammatory bowel diseases (IBDs) are chronic disorders of the gastrointestinal tract with the following two subtypes: Crohn's disease (CD) and ulcerative colitis (UC). To date, most IBD genetic associations were derived from individuals of European (EUR) ancestries. Here we report the largest IBD study of individuals of East Asian (EAS) ancestries, including 14,393 cases and 15,456 controls. We found 80 IBD loci in EAS alone and 320 when meta-analyzed with ~370,000 EUR individuals (~30,000 cases), among which 81 are new. EAS-enriched coding variants implicate many new IBD genes, including ADAP1 and GIT2. Although IBD genetic effects are generally consistent across ancestries, genetics underlying CD appears more ancestry dependent than UC, driven by allele frequency (NOD2) and effect (TNFSF15). We extended the IBD polygenic risk score (PRS) by incorporating both ancestries, greatly improving its accuracy and highlighting the importance of diversity for the equitable deployment of PRS.Inflammatory bowel diseases (IBDs) are a group of chronic, debilitating disorders of the gastrointestinal tract with the peak onset in adolescence and early adulthood 1 . As of 2017, there were 6.8 million people diagnosed with IBD globally 2 , with increasing incidence and prevalence worldwide, especially in recently industrialized countries, likely due to the modernization and westernization of the populations 2,3 . IBDs have the following two etiologically related subtypes: Crohn's disease (CD) and ulcerative colitis (UC). Genome-wide association studies (GWAS) have discovered over 240 genetic loci associated with IBD 4 . However, to date, most IBD genetic associations have been derived using individuals of European (EUR) ancestries 4,5 , with only a few studies of much smaller sample sizes in non-EUR populations [6][7][8] . For example, the largest IBD GWAS in African 9 and Asian 7 populations included 2,345 and 3,195 cases, respectively, only about 10% of the number in the largest EUR IBD GWAS (29,336) 4 . Among the ImmunoChip samples, a cohort that was uniformly processed and drove several large-scale IBD genetics studies 6,10-12 , 87% of patients were of EUR ancestries, with the remaining 13% from Asian (7%), Indian (4%) and Iranian (2%) ancestries, respectively. This strong bias toward EUR severely limits our