Crohn's disease linked with asthma


32 genes increase the risk of Crohn's disease, including one linked to asthma

A surprising link between Crohn's disease and asthma has been discovered by scientists looking into the genetic causes of the bowel disorder.

Researchers found that a gene called ORMDL3, known to be a risk factor for childhood asthma, was also associated with Crohn's.

Links between the condition and other diseases were also uncovered by the study, which found a clutch of new Crohn's related genes.

Crohn's is an auto-immune disease that affects between one in 500 and one in 1,000 people in the UK, causing inflammation of the gut leading to pain, ulcers and diarrhoea.

Evidence suggests that the disorder is complex and affected by large numbers of genes.

Previous studies had already identified 11 genes and loci - sections of DNA where one or more unknown genes may reside - that increase susceptibility to the disease.

The new research has expanded that number to 32.

Scientists believe they have uncovered a number of biological processes that could be targeted by new therapeutic drugs.

Study leader Dr Jeffrey Barrett, from the Wellcome Trust Centre for Human Genetics at Oxford University, said: 'We now know of more than 30 genetic regions that affect susceptibility to Crohn's disease.

'These explain only about a fifth of the genetic risk, which implies that there may be hundreds of genes implicated in the disease, each increasing susceptibility by a small amount.

'Whilst this study shows the power of genome-wide association studies to reveal the genetics behind common diseases, it also highlights the complexity of diseases such as Crohn's.'

The discoveries were made using DNA samples from almost 12,000 people from the UK, continental Europe and the US.

Among the findings are loci containing genes known to be implicated in type 1 diabetes, rheumatoid arthritis and psoriasis. Like Crohn's, all these diseases involve the body's immune system attacking its own tissues.

The connections are not always straightforward, however. For instance, the genetic variant PTPN2 appears to increase susceptibility both to Crohn's and type 1 diabetes.

Yet the variant PTPN22 increases the risk of type 1 diabetes while offering protection

against Crohn's.

To date no association has been seen in patterns of childhood asthma and Crohn's.
Yet the ORMDL3 gene on chromosome 17 appears to be involved in both diseases.

Dr Miles Parkes, consultant gastroenterologist at Addenbrooke's Hospital, Cambridge, who also took part in the research, said: 'It's too early for us to say how Crohn's disease and many of these other diseases, including asthma, are linked at a biological level.

'However, we are building up a picture of the biology underlying Crohn's disease, and the more we understand about the underlying biology of these diseases, the better equipped we will be to treat them.

'Studies such as this are not about developing diagnostic tests, but about identifying targets for new drugs therapies. Crohn's disease can be a very serious condition, often requiring surgery, and the sooner we are able to identify new ways to treat it, the sooner we are able to help those affected by the disease.'

One possible treatment target is the gene CCR6, which is thought to be part of the signalling machinery that causes specific immune system cells in the gut to become over-active. These white blood cells, known as Th17 cells, are also present in inflamed arthritic joints.

'Genetics, and particularly the large scale approach of genome-wide association studies, offers much hope for understanding the biological causes of complex diseases,' said Dr Mark Walport, director of the Wellcome Trust.

'Studies such as this also highlight the important relationships between different diseases and, as such, may offer valuable insights into the pathways that lead to common symptoms such as inflammation.'

No comments have so far been submitted. Why not be the first to send us your thoughts, or debate this issue live on our message boards.

We are no longer accepting comments on this article.

Who is this week's top commenter? Find out now