A new study queries the role of allergy in the development of asthma, and suggests that a different disease process is involved in childhood and adult-onset asthma. Asthma is a complex condition with genetic and environmental factors, although experts believe it has a strong heritable component.
The researchers based at Imperial College London, performed a genome-wide association study (GWAS) on over 26,000 people and identified seven key areas associated with the development of asthma.
They discovered that genes, that were closely linked to asthma were involved in signalling in the immune system, particularly in relation to damage to the lining of the airway and inflammation. However, genetic markers associated with elevated levels of the antibody, IgE (Immunoglobulin E), which plays an important role in allergy, were not found to be associated with asthma.
The researchers also found that two genes, ORMDL3 and GSDBM, were specifically associated with childhood-onset asthma.
The findings suggest that allergy is a disease-related process rather than a cause of asthma.
Professor William Cookson, a respiratory geneticist at Imperial, who led the study said: 'About 60 per cent of people with asthma suffer from some form of allergy; there has always been a close relationship. It has always been assumed that allergies are driving the process and that is where the focus of research has been, without too much success'.
Professor Miriam Moffatt, also from Imperial College London and one of the primary investigators said: 'This does not mean that allergies are not important, but it does mean that concentrating therapies only on allergy will not effectively treat the whole disease'.
The authors concluded that although some of the genetic markers were associated with both early and late-onset asthma, the condition appears to be genetically heterogeneous. In other words, childhood-onset and adult-onset asthma have a different genetic profile.
Although the genetic markers associated with asthma in this study cannot be used to determine individual risk, together they were estimated to account for 38 per cent of all the childhood-onset cases in the study.
Professor Cookson said: 'Our study now highlights targets for effective asthma therapies, and suggests that therapies against these targets will be of use to large numbers of asthmatics'.
The research was published in the September issue of the New England Journal of Medicine.