Previously identified as a significant risk factor for eczema, asthma, allergic rhinitis, and certain food sensitivities, a mutation of the “Filaggrin” gene makes carriers three times as likely to suffer peanut allergy, according to an international research collaboration led by the University of Dundee, Scotland.
The Filaggrin gene normally codes for a protein that helps the skin (and the linings of the intestinal tract and respiratory tract - all ‘epithelial’ tissues) act as a good barrier against irritants, toxins, and allergens; while changes in the gene reduce the effectiveness of this barrier and lead to a range of allergic conditions.
The mutation was found in about 20% of peanut allergy sufferers tested in Canada, Ireland, England, and the Netherlands, according to the study report, published by the Journal of Allergy and Clinical Immunology. (See free full text, “Loss-of-function variants in the Filaggrin gene are a significant risk factor for peanut allergy.”)
After their discovery of the mutation’s role in causing eczema and asthma, “it was a logical next step to investigate whether Filaggrin may also be a cause of peanut allergy, since a child may develop all three of these diseases together,” says lead author Sara Brown, MD, a Wellcome Trust Intermediate Clinical Fellow in the Division of Molecular Medicine at Dundee.
“Allergic conditions often run in families, which tells us that inherited genetic factors are important,” Dr. Brown explains. “In addition to that, changes in the environment and our exposure to peanuts are thought to have been responsible for the recent increase in peanut allergy seen in the western world in particular.” (Peanut allergy affects 1%-2% of children in the UK, for example, representing a dramatic increase over the past 20 to 30 years.)
“Now, for the first time, we have a genetic change that can be firmly linked to peanut allergy.”
“We knew that people with a Filaggrin defect were likely to suffer from eczema, and that many of those people also had peanut allergy,” adds Prof. Irwin McLean, one of the world’s leading authorities on Filaggrin, also based at Dundee.
“What we have now shown is that the Filaggrin defect is there for people who have peanut allergy but who don’t have eczema, which shows a clear link between Filaggrin and peanut allergy," he adds.
“The Filaggrin defect is not THE cause of peanut allergy but we have established it as a factor in many cases. We don’t yet know enough about the causes of peanut allergy but this is an important step forward.”
And since Filaggrin defects were found in only 20% of the peanut allergy cases, a lot of work is still needed to fully understand the genetic risk factors for this complex disease.
[Note: Other recent research points to a possible association between Filaggrin defects, eczema and type 2 diabetes in a random sample of 3,335 adults in Denmark. ]
Source: University of Dundee news release, Mar 2011