To what extent are genetics clinically useful?

The volume of research undertaken on the genetic susceptibility of inflammatory bowel diseases has been tremendous. International collaborative efforts which initiated in 1997 and have not stopped since, led to the identification at present of more than 100 IBD risk loci. Yet, only 25% of the genetic variance is explained. It is hypothesized that rare variants, other forms of genetic variation (copy number variation), as well as gene-gene and geneenvironment interactions, explain the missing heritability. From all genes identified, the pattern recognition receptor NOD2/CARD15 is still the most understood at present. The field of IBD genetics has translated itself so far in identifying pathways important for disease pathogenesis (autophagy, Th17/IL23, pattern recognition receptors and innate immunity, barrier integrity), some of which have promising therapeutic consequences. Second, although genetic testing will most likely have no or a very limited role in diagnosing patients, it is anticipated that genetic markers will be implemented in an integrated prognostic approach. Efforts to predict disease course and response to therapy have shown interesting results.