Relationship between serum interleukin-31/25-hydroxyvitamin D levels and the severity of atopic dermatitis in children

Purpose: Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease. Vitamin D and interleukin-31 (IL-31) are known to be related to the pathogenesis of AD with pruritus. The purpose of this study was to investigate the relationship between serum levels of 25-hydroxyvitamin D (25(OH) D) and IL-31 and the disease severity of AD in children with AD. Methods: We recruited 160 children with AD and 42 controls. We used the SCORing Atopic Dermatitis (SCORAD) index to measure the severity of AD. Serum IL-31 and 25(OH) D levels were assayed using enzyme-linked immunosorbent assay and high-performance liquid chromatography, respectively. Serum levels of total IgE, specific IgE to common allergens and peripheral blood total eosinophil count were carried out in children with AD. Results: Serum IL-31 level was significantly higher in AD group compared to control group and 25(OH) D level was significantly lower in AD group than control group. Serum IL-31 level showed the highest level in severe AD group followed by moderate and mild AD group, whilst serum 25(OH) D level was the lowest in severe AD group compared to moderate and mild AD group. There was no difference in serum IL-31 level between AD group and nonatopic dermatitis group. IL-31 level was positively correlated with subjective SCORAD index indicating pruritus in children with AD, and 25(OH) D was inversely correlated with SCORAD index. Conclusion: IL-31 and vitamin D may be related to the pathogenesis of AD, especially with regard to the pruritus.