Effects of Phototherapy on Free Vitamin D Levels in Ten Patients with Atopic Dermatitis

The role of vitamin D in atopic dermatitis (AD) is controversial. Conflicting data could be due to the use of inadequate markers for assessing vitamin D status. So far, directly measured free 25(OH)D concentrations have not been reported in AD patients. Ten adults with AD were treated with narrow band ultraviolet light B (NB-UVB) for 10–12 weeks. SCORing atopic dermatitis (SCORAD) and the visual analogue scale (VAS) were used to assess disease severity before and after NB-UVB therapy. Total and free 25(OH)D and 1,25(OH)2D serum levels were analyzed before and after treatment. Free 25(OH)D concentrations were measured with a two-step immunosorbent assay (ELISA). The majority of patients had sufficient levels of 25(OH)D before treatment (mean 76.4 nmol/L). Mean free 25(OH)D was 11.9 pmol/L and mean 1,25(OH)2D was 108.9 pmol/L. Median SCORAD decreased from 37.1 to 19.8 and VAS improved significantly after phototherapy. Total and free 25(OH)D increased in all subjects. No correlations between disease severity and vitamin D levels were found. There was no correlation between total and free 25(OH)D levels. Larger studies are needed to test the applicability of the free hormone hypothesis in AD pathogenesis.