The fact that healthy relatives of those affected by inflammatory bowel disease (IBD) have an increased risk of developing Crohn’s disease (CD) and have greater dysbiosis (imbalance between the number or proportion of friendly microorganisms and pathogens within the human intestine) It indicates that both the genetics and alterations of the intestinal microbiome can trigger the phenotype of the disease.

A study led by Professor Kevin Whelan of the Faculty of Life Sciences and Medicine of King’s College London (United Kingdom) found that healthy people at risk of Crohn’s disease show a dysbiosis of microbiota associated with the mucosa with a lower abundance of Faecalibacterium prausnitzii.

The researchers studied the influence of genotypic and phenotypic factors on the intestinal microbiota and characterized it of the mucosa in 21 patients with inactive Crohn’s disease, 17 healthy young siblings of patients with pathology and another 19 unrelated healthy participants. The microbiota of both CD patients and their healthy siblings was significantly less diverse compared to that of the unrelated healthy controls. In fact, the composition was more similar between patients and their healthy siblings than between siblings without the disease and healthy controls. These findings suggest that dysbiosis of the gut microbiota in healthy relatives, but genetically predisposed, could influence the pathogenesis of the disease, instead of simply being a consequence of the pathology.

The reduction of Faecalibacterium prausnitzii contributed the most to the difference in the composition of the mucosa-associated microbiota between patients and siblings compared to healthy controls.