Genetic skin defect ups allergy risk

[Posted: Wed 06/08/2008]

A genetic defect in the skin appears to play a key role in the development of allergies, the results of a new study indicate.

Allergic conditions, such as atopic dermatitis (also known as eczema), asthma and hay fever, have increased significantly in recent years, particularly in most industrialised countries. A combination of genetic and environmental factors are thought to be the cause.

According to a team of international researchers, in recent years, several genes were examined for a role in allergic diseases and one of them actually turned out to be a key player. This gene encodes filaggrin, an essential protein found in the skin. If this protein is reduced or lacking due to a genetic defect, the natural barrier function of the skin is limited.

In 2006, Irish researchers discovered that filaggrin mutations were the cause of the skin disease, ichthyosis vulgaris, also known as ‘fish scale disease’. They also found that these mutations were risk factors for the development of atopic dermatitis.

In this latest study, the researchers investigated 3,000 school children in Munich, Germany. They found that almost 8% of the children suffered from a genetically determined deficiency of filaggrin protein in the skin. These children were more than three times as likely to develop atopic dermatitis compared to children without the mutation.

In addition, those with the genetic mutation and atopic dermatitis were predisposed to develop asthma and hay fever.

"In general, our results show that mutations in the filaggrin gene are extremely strong risk factors for atopic dermatitis and beyond that for hay fever. In the case of pre-existing eczema they may also cause asthma," explained Dr Stephan Weidinger of the Technische Universität München.

He pointed out that the results in relation to asthma were surprising because filiggrin is not present in the respiratory tract and appears to be of importance in the skin only.

"A weakened skin barrier function might enable allergens to penetrate more easily and thereby promote the development of allergies,” he suggested.

In a recent study of 1,600 adults, the researchers found that a deficiency of a filaggrin protein due to genetic variants also increased the risk of allergic contact eczema, especially of allergic reactions to nickel, which is often found in costume jewellery.

They said that the current findings show that the skin plays a crucial role in the development of different allergic diseases.

"We are now interested in finding out the precise consequences of filaggrin mutations. The next thing to do is to examine the metabolic pathway of this important protein. The final aim, of course, is to find a therapy for patients with atopic diseases.

“If a lack of filaggrin is such an important factor in allergic diseases, it would be almost conceivable to increase production of this protein or to replace its function in other ways,” added Dr Thomas Illig of the Helmholtz Zentrum München.

Details of these findings are published in Pharmacogenomics.

For more information on asthma, click on… http://www.irishhealth.com/clin/asthma/index.html

For more information on eczema, click on… http://www.irishhealth.com/clin/eczema/