Very recently, a sub-analysis of genome-wide association scans revealed that the non-coding single nucleotide polymorphism (SNP) rs12212067 in the FOXO3A gene is associated with a milder course of Crohn's disease (CD) (Cell 2013;155:57–69). The aim of our study was to evaluate the clinical value of the SNP rs12212067 in predicting the severity of CD by correlating CD patient genotype status with the most relevant complications of CD such as stenoses, fistulas, and CD-related surgery.
We genotyped 550 CD patients for rs12212067 (FOXO3A) and the three common CD-associated NOD2 mutations rs2066844, rs2066847, and rs2066847 and performed genotype-phenotype analyses.
No significant phenotypic differences were found between the wild-type genotype TT of the FOXO3A SNP rs12212067 and the minor genotypes TG and GG independently from NOD2 variants. The allele frequency of the minor G allele was 12.7%. Age at diagnosis, disease duration, body mass index, surgery rate, stenoses, fistula, need for immunosuppressive therapy, and disease course were not significantly different. In contrast, the NOD2 mutant p.Leu1007fsX1008 (rs2066847) was highly associated with penetrating CD (p = 0.01), the development of fistulas (p = 0.01) and stenoses (p = 0.01), and ileal disease localization (p = 0.03). Importantly, the NOD2 SNP rs2066847 was a strong separator between an aggressive and a mild course of CD (p = 2.99×10−5), while the FOXO3A SNP rs12212067 did not separate between mild and aggressive CD behavior in our cohort (p = 0.35). 96.2% of the homozygous NOD2 p.Leu1007fsX1008 carriers had an aggressive disease behavior compared to 69.3% of the patients with the NOD2 wild-type genotype (p = 0.007).
In clinical practice, the NOD2 variant p.Leu1007fsX1008 (rs2066847), in particular in homozygous form, is a much stronger marker for a severe clinical phenotype than the FOXO3A rs12212067 SNP for a mild disease course on an individual patient level despite its important impact on the inflammatory response of monocytes.