CARD15 and IL23R influences Crohn's disease susceptibility but not disease phenotype in a Brazilian population

Background: Although many genetic variants are identified in association with Crohn's disease (CD), CARD15, IL23R, and ATG16L1 association with CD have been firmly confirmed in Caucasians of European ancestry. The prevalence of CD is rapidly rising in Brazil, where European ancestry is firmly admixed with natives and Africans, resulting in a heterogeneous population. We investigated the contribution of CARD15, IL23R, and ATG16L1 with CD risk in a heterogeneous Brazilian population. Methods: Genotyping for CARD15 (R702W, G908R, 3020insC), IL23R (rs1004819, rs7517847, rs11209026, rs10889677, rs1495965), and ATG16L1 (rs2241880) was performed in 187 children and adults with CD and 255 healthy ethnically matched controls. Clinical records were systematically reviewed and detailed phenotypic information was obtained. Results: At least 1 CARD15 risk allele was present in 30% of the CD patients compared with 10% of controls. Variants of CARD15 (3020insC and R702W) and IL23R (rs1004819, rs11209026, and rs1088967) were associated with CD. However, no genotype-phenotype correlations were found among the Brazilian CD population with CARD15 or IL23R variants. No significant association was achieved with ATG16L1. Conclusions: CARD15 and IL23R confer susceptibility to CD in the Brazilian population. However, the presence of these variants did not influence disease phenotype. Further research should be focused on larger sample sizes with population admixture analysis to better understand the risks and genotype-phenotype correlation in populations like Brazil where the prevalence of CD is rapidly rising.