From the Journals

Skin barrier dysfunction mutations vary by race, disease persistence in children with AD



Among children with atopic dermatitis, genetic variants associated with skin barrier dysfunction vary significantly by race and by their influence on disease persistence, according to authors of a cohort study.

In the study, which was based on data from a pediatric eczema registry, white children with atopic dermatitis (AD) were more than twice as likely as black children to have a filaggrin gene (FLG) loss-of-function (LoF) variant. The investigators remarked on “profound” differences by race in the study, which used a high-throughput sequencing method to identify FLG LoF variants, some of which were common in white children but not so frequently seen in black children.

Conversely, some variants common in black children were completely absent in the white children, according to the investigators, led by David J. Margolis, MD, PhD, professor of dermatology at the University of Pennsylvania, Philadelphia. The study was published in JAMA Dermatology.

These findings imply that any genetic tests developed for AD should be “inclusive,” they wrote, and shouldn’t simply rely on the most common variants associated with patients of European ancestry, namely p.R501*, c.2282del4[p.S761fs], p.S3247*, and p.R2447*.

“Relying on the classic 4 FLG LoF variants would result in approximately 8% of white children and 64% of black children with an FLG LoF variant being improperly classified,” Dr. Margolis and coinvestigators wrote.

Their comprehensive analysis of FLG LoF variants was based on a U.S. cohort of 741 children with mild to moderate AD in the Pediatric Eczema Elective Registry (PEER), enrolled from 2005 to 2017. The mean age of onset of AD among the children was almost 2 years. Using massively parallel sequencing, the investigators identified a total of 23 FLG LoF variants in 177 children, or 23.9% of the overall cohort.

White children had a higher frequency of FLG LoF variants, according to the investigators. The prevalence of variants was 31.5% in white and 15.3% in black participants, translating into an odds ratio of 2.44 for carrying any variant in a white versus black child (95% confidence interval, 1.76-3.39).

In previous studies, FLG LoF variants are seen in 25%-30% of people with AD who have European and Asian ancestry; by contrast, they are “uncommonly” exhibited in individuals of African ancestry, the investigators wrote.

Persistent AD was more likely among children with FLG LoF variants, with an odds ratio of 0.67 (95% CI, 0.56-0.80), according to Dr. Margolis and coauthors. However, the black children in this cohort had more persistent disease, compared with white children, regardless of whether they had FLG LoF variants or not.

Exon 3 FLG LoF are known to be the most common variants linked to skin barrier dysfunction, the investigators noted.

“However, all FLG LoF variants might not confer an increased risk of AD, and further, they may not all have the same effect on the persistence of AD over time,” they added in a discussion of their results.

The study was supported by a grant from the National Institute of Arthritis and Musculoskeletal and Skin Diseases. The PEER cohort is funded by Valeant Pharmaceuticals. Dr. Margolis reported receiving research funding as the principal investigator via the trustees of the University of Pennsylvania, and receiving funding from the National Institutes of Health and Valeant; disclosures not related to the study included consulting activities primarily as a member of a data monitoring or scientific advisory boards for several pharmaceutical companies.

SOURCE: Margolis DJ et al. JAMA Dermatol. 2019 Jul 31. doi: 10.1011/jamadermatol.2019.1946.

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