Copy‐number variation of the filaggrin gene in Korean patients with atopic dermatitis: what really matters, ‘number’ or ‘variation’?

DEAR EDITOR, Since the articles reporting a methodological breakthrough on the full sequencing of the gene encoding profilaggrin (FLG), associations between loss-of-function mutations of FLG and atopic dermatitis (AD) have been reported across ethnicities. However, both the low prevalence of FLG mutations in patients with AD in some nations (< 4% in Italy) and the high prevalence of FLG mutations in healthy control in other nations (~ 10% in Ireland) suggest that factors other than FLG mutation may be at work. Brown et al. introduced an interesting new factor contributing to the risk of AD: copynumber variation aa(CNV). FLG is polymorphic, with allelic variants of 10–12 nearly identical repeats in exon 3. They