CARD15 mutations in Dutch familial and sporadic inflammatory bowel disease and an overview of European studies

OBJECTIVES: The single nucleotide variations R702W, G908R and L1007fs in the CARD15 gene have been found to be independently associated with Crohn's disease. The aim of this study was to evaluate the prevalence of these gene variations in Dutch multiple inflammatory bowel disease-affected families, in sporadic inflammatory bowel disease patients and in healthy controls. METHODS: Dutch Caucasians from multiple inflammatory bowel disease-affected families were recruited, including 78 probands with Crohn's disease, 34 probands with ulcerative colitis and 71 inflammatory bowel disease-affected and 100 non-affected family members. In addition, 45 sporadic inflammatory bowel disease patients (36 Crohn's disease and nine ulcerative colitis), and 77 unrelated healthy controls were included. Genomic DNA was isolated to determine CARD15 R702W, G908R and L1007fs. For these mutations, we evaluated disease susceptibility and correlation with inflammatory bowel disease phenotypes. RESULTS: In all included unrelated inflammatory bowel disease-affected probands, the R702W, G908R and L1007fs allele frequencies were 8.8, 6.1 and 11.0%, respectively, for Crohn's disease, and 4.7, 0 and 2.3% for ulcerative colitis. In controls, the allele frequencies were 5.9, 0.7 and 1.9%, respectively. G908R and L1007fs were associated with Crohn's disease (P=0.006 and 0.001, respectively). Compound heterozygotes for any of the three mutations were 11 (9.2%) in Crohn's disease patients, but none in ulcerative colitis patients nor controls. Carriage of CARD15 mutations was not associated with familial disease (P≥0.38). Inflammatory bowel disease-affected family members of Crohn's disease probands carrying L1007fs, however, were carriers significantly more often than expected (P<0.001). In Crohn's disease patients, a significant trend was found between carriage of at least one CARD15 mutation and between carriage of L1007fs and behaviour of disease, including more carriers with stricturing and even more with penetrating disease (P=0.006 and 0.017, respectively). CONCLUSION: In the Dutch population, CARD15 G908R and L1007fs are associated with Crohn's disease. Although no difference was found between sporadic and familial cases, in L1007fs-positive multiple affected families the inflammatory bowel disease-affected relatives are more likely than expected to carry this mutation. In Crohn's disease, carriage of at least one CARD15 mutation is associated with a more complicated disease behaviour.

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