NOD2/CARD15 mutations in Croatian patients with Crohn's disease: prevalence and genotype-phenotype relationship

Background Crohn's disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract with variations in localization and behaviour. Mutations in the NOD2/CARD15 gene on chromosome 16q have been implicated in the pathogenesis of the disease and three main sequence variants, all single nucleotide polymorphisms (SNPs), have been identified in North American and European populations. Aims and methods As no data exist in the Croatian population, we consecutively collected a cohort of 136 CD patients and 91 healthy controls to determine the prevalence of NOD2/CARD15 mutations and their association with phenotypic expression of the disease. All patients and controls were genotyped for Arg702Trp (Hugot SNP8), Gly9O8Arg (Hugot SNP12), and Leu1007fsinsC (Hugot SNP13) and allele frequencies were compared between the Crohn's patients and controls. The correlation of NOD2/CARD15 genotypes with the phenotypic expression of Crohn's disease was further assessed by logistic regression analysis. Results NOD2/CARD15 variants were found in 38/136 CD patients (27.9%) compared to 10/91 (10.9%) healthy controls (P=0.0022). Allele frequencies in patients with CD were 13.97%, 4.4% and 11.76%, respectively, for SNP8,12 and 13, compared to 5.49%,1.12% and 4.40% in controls (P= 0.041, P= 0.162, P= 0.055). Six CD patients carried double mutations and, remarkably, we identified twohomozygous mutants amongst the healthy control group. Surgery over the course of the disease and a younger age at onset of the disease were significantly more frequent in patients who were carriers of NOD2/CARD15 mutations. Conclusions This report on NOD2/CARD15 mutations in Croatian patients with CD demonstrates that this gene is also implicated in susceptibility to CD in the Croatian population. Phenotypic association showed a younger age at diagnosis and a higher need for surgery in patients carrying NOD2/CARD15 mutations. However, the prevalence is somewhat lower compared to other reports, likely due to a more prominent colonic inflammation.