Filaggrin mutation means more persistent eczema

The super-protein filaggrin helps skin cells take their proper shape as they develop into the upper, outer layer of skin; in its last step, it disintegrates into molecules that help the skin lock in moisture. Back in 2006 a landmark discovery showed that mutations in the filaggrin gene made it likely that the gene’s owner would develop eczema. But even though filaggrin is the poster child for eczema genetics, not that many eczema patients—only about 15%—have mutated copies of the gene.

Now researchers led by David Margolis, a professor of dermatology at the University of Pennsylvania, have shown that, among children with eczema, those who have filaggrin mutations are more likely to experience persistent eczema symptoms than those who do not.

The scientists analyzed data from the Pediatric Eczema Elective Registry (PEER), an ongoing 10-year registry maintained by Novartis to monitor the long-term safety of using pimecrolimus 1% cream. The new results are in press at the Journal of Allergy and Clinical Immunology.

The difference is subtle: at any time up to about four years of follow up (the period covered by the study), a child with a filaggrin mutation and a history of eczema is roughly 50% less likely to have clear skin than a child with two good copies of filaggrin. [Thanks to Margolis for helping me understand odds ratio.]

Interestingly, the authors noted that although all the mutations they studied were “null” mutations—that is, if you have one of these mutations, that copy of filaggrin doesn’t get produced at all—children with different mutations responded differently to treatment with topical steroids. Kids with the most common mutation, R501X, were most likely to need to use steroids to clear their skin. The authors don’t have an answer why this might be so.