In this issue of the Archives, Ryan et al1 report the results of a well-designed prospective controlled study of patients with psoriasis from an outpatient dermatology department based in Dublin, Ireland. The UV-mediated increase in serum 25-hydroxyvitamin D [25(OH)D] was assessed in 30 patients with chronic plaque psoriasis at baseline, after 4 weeks, and on completion of treatment with narrowband UV-B (NB–UV-B) therapy during wintertime and compared with a control group of patients who had not been treated with phototherapy. In the NB–UV-B treatment group, there was a significant increase (P < .001) in the levels of serum 25(OH)D from a median of 23 ng/mL at baseline to 50 ng/mL at the end of NB–UV-B therapy [to convert 25(OH)D to nanomoles per milliliter, multiply by 2.496]; the median psoriasis area and severity index (PASI) significantly decreased following NB–UV-B from 7.1 at baseline to 0.5 (P < .001), and the median Dermatology Life Quality Index (DLQI) decreased from 10 to 1 (P < .001). In contrast, the median serum vitamin D value, PASI, and DLQI remained unchanged in the control group. By the end of the study, all patients in the treatment group were found to have sufficient levels of vitamin D. Seventy-five percent of the control group had serum 25(OH)D levels of less than 20 ng/mL, suggesting that these patients with psoriasis had vitamin D insufficiency during wintertime. The study further showed that the number of exposures of NB–UV-B was the sole predictor of increase in serum 25(OH)D level; the number and a history of phototherapy was the only predictor of baseline serum 25(OH)D levels.
Vemulapalli P, Lim HW. Phototherapy and Vitamin D. Arch Dermatol. 2010;146(8):906-908. doi:10.1001/archdermatol.2010.193