A child’s risk of developing eczema in the first year can be increased by a combination of a specific genetic mutation in the protein filaggrin (FLG) and exposure to a cat, according to a study released on June 23, 2008 in the open access journal PLoS Medicine.

Eczema is a skin disease characterized by inflammation of the outer layers of the skin, and symptoms include dry, red, and itchy patches on the skin. It generally runs in families, thus having a genetic component, but it is also widely considered to be caused by environmental factors as well. Previously, it has been shown that two common variants in the gene encoding filaggrin predispose people to eczema. Filaggrin, normally found in skin cells, is a filamentous protein that serves a protective function by acting as a physical barrier to harmful substances in the environment.

A team, led by Professor Hans Bisgaard of the University Hospital Gentofte, Copenhagen, Denmark, hypothesized that the loss of these genes weakens this physical barrier, thus affecting the response to environmental substances. To investigate this, the team performed a cohort study in two groups of infants: the first, with 379 infants, were born to mothers with asthma, and the second, with 503 babies, came from women in the general population. The children were examined for FLG variants, and classified with either one or two defective copies of FLG. Additionally, the families were asked if a dog or cat was living in the home when the child was born, and this information was correlated with the age of onset of eczema.

In both groups of children, the infants with FLG mutations were twice as likely to develop eczema in the first year of life as those without. However, for children with FLG mutations only, cat ownership at birth increased the risk of developing eczema more. This was not seen in dog owners or in children without FLG mutations. Allergies were examined via the presence of cat-specific antibodies, and were not found to contribute to this effect.

According to the researchers, these results suggest that filaggrin deficiency weakens the skin’s protective barrier, but it is not clear why exposure to cats should drive the development of eczema.The study was limited by the small number of infants examined with FLG mutations who had also been exposed to cats at birth, and thus should be repeated with larger numbers of infants. However, if confirmed, these results could suggest that filaggrin deficient children should avoid cats early in life.

About PLoS Medicine

PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org.

About the Public Library of Science

The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world’s scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org.

Gene-environment interaction in the onset of eczema in infancy: Filaggrin loss-of-function mutations enhanced by neonatal cat exposure.
Bisgaard H, Simpson A, Palmer CNA, Bnnelykke K, Mclean I, et al.
PLoS Med 5(6): e131.
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Written by Anna Sophia McKenney