Palmar hyperlinearity in early childhood atopic dermatitis is associated with filaggrin mutation and sensitization to egg

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background/Objectives</jats:title><jats:p>Palmar hyperlinearity is a typical clinical feature of <jats:italic>Filaggrin gene</jats:italic> (<jats:italic><jats:styled-content style="fixed-case">FLG</jats:styled-content></jats:italic>) null mutations. There are reports of <jats:italic><jats:styled-content style="fixed-case">FLG</jats:styled-content></jats:italic> mutations and allergic sensitization; however, reports on the relationship between palmar hyperlinearity to sensitization are limited. This study aimed to examine the association between palmar hyperlinearity and sensitization in atopic dermatitis (<jats:styled-content style="fixed-case">AD</jats:styled-content>) children.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>This cross‐sectional, case‐control study included children ˂ 6 years old with moderate‐severe <jats:styled-content style="fixed-case">AD</jats:styled-content> whose parents consented for mutation analysis and photographic documentation. Each child underwent genotyping to detect the eight most prevalent <jats:italic><jats:styled-content style="fixed-case">FLG</jats:styled-content></jats:italic> mutations in the Japanese population: R501X, 3321delA, S1695X, Q1701X, S2554X, S2889X, S3296X, and K4022X. Clinical features and parameters including egg‐specific IgE were examined, and palm photographs were evaluated by 12 trained dermatologists blinded to genotyping results.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Of the 57 patients (age range, 2 months to 5 years; median, 22 months), 16 were heterozygotes and three were compound heterozygotes. Palmar hyperlinearity, as recognized by more than two‐thirds of dermatologists, was significantly associated with <jats:italic><jats:styled-content style="fixed-case">FLG</jats:styled-content></jats:italic> mutation (<jats:italic>P</jats:italic> = 0.002, <jats:styled-content style="fixed-case">OR</jats:styled-content> = 6.98, 95% <jats:styled-content style="fixed-case">CI</jats:styled-content> = 2.1‐23.7), and this association was observed especially in children over 2 years. Cross‐shaped crease of the thenar eminence, as known in previous reports, also demonstrated significant correlation with <jats:italic><jats:styled-content style="fixed-case">FLG</jats:styled-content></jats:italic> mutation. When the children were divided according to the presence or absence of palmar hyperlinearity, the egg white–specific IgE was significantly higher in the hyperlinearity group (55.9 vs 18.3 IU/mL, <jats:italic>P</jats:italic> < 0.05).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Palmar hyperlinearity indicates possible inherited barrier abnormalities of the skin in early childhood. Its identification may help to predict a more accurate prognosis, such as sensitization.</jats:p></jats:sec>