Linoleic acid metabolite levels and transepidermal water loss in children with atopic dermatitis

Background: It has been suggested that atopic dermatitis (AD) is associated with impaired 8-6 desaturase activity and the subsequent altered composition of n-6 essential fatty acids (EFAs). Objective: To investigate whether n-6 EFA deficiency accounts for AD by affecting transepidermal water loss or the immune response. Methods: Serum levels of n-6 EFAs were measured using gas chromatography-mass spectrometry in a well-defined group of 35 children with AD (IgE level > 150 U/mL); 35 age-matched children with allergic rhinitis, asthma, or both (IgE level > 150 U/mL); and 31 nonatopic controls (IgE level < 100 U/mL). Skin barrier function was evaluated by measuring transepidermal water loss and severity of AD by computing the Scoring Atopic Dermatitis (SCORAD) index. Results: Atopic children had higher levels of linoleic acid (LA) and lower levels of its metabolites. Furthermore, gamma-linolenic acid to LA and dihommo-gamma-linolenic acid to LA ratios were significantly reduced in atopic patients. Transepidermal water loss and the SCORAD index were negatively correlated with serum levels of LA metabolites. There was no correlation between the SCORAD index and IgE level (P =.51) or between n-6 EFA concentrations and IgE level (P >.10). Conclusions: Deficits in n-6 EFAs were correlated with the severity of AD by affecting skin barrier function and cutaneous inflammation. The link between impaired n-6 EFA metabolism and IgE level could not be defined.