Efficacy of narrowband ultraviolet B phototherapy and levels of serum vitamin D3 in psoriasis: A prospective study

Introduction: Narrowband ultraviolet B phototherapy (NBUVB) is safe and effective treatment for psoriasis. Vitamin D plays an important role in pathogenesis of psoriasis. It is known that psoriasis patients have low serum 25(OH)D levels, which increase after NBUVB. We assessed serum 25(OH)D levels, its correlation with Psoriasis Area and Severity Index (PASI), and the effect of NBUVB on 25(OH)D levels among Indian psoriasis patients.

Materials and methods: A prospective study comprising 30 adults with psoriasis with no major comorbidities (PASI > 10 and off-therapy >4 weeks) was conducted. PASI was estimated at baseline among patients and repeated after receiving 12 weeks of NBUVB therapy. Thirty age and gender-matched healthy controls were recruited to compare 25(OH)D levels at baseline and at 12 weeks. Patient demographic parameters, treatment dose, duration, side effects, and its impact on 25(OH)D levels and PASI were serially evaluated.

Results: A total of 30 patients presenting with psoriasis and 30 healthy controls were enrolled in the study. Mean baseline PASI (M: F =19:11) among patients with mean age 36.8 (±7.7) years was 20.5 (±6.3) and all patients were either 25(OH)D deficient (n = 14) or insufficient (n = 16). Their baseline 25(OH)D levels were significantly lower than controls (25.93 nmol/L vs 47.54 nmol/L; P < 0.001). After NBUVB therapy (average cumulative dose 20.76 ± 7.1 J/cm(2); average treatment sessions 32.57 ± 1.9), there was a significant improvement in PASI as well as 25(OH)D (P < 0.05). There was no correlation between the mean improvement in PASI and 25(OH)D after 12 weeks of therapy. Twelve (40%) patients had therapy-related side effects [pruritus (n = 8), erythema (n = 4)], none had major side effects.

Conclusion: Improvement in PASI and serum 25(OH)D levels after NBUVB in psoriasis is significant but poorly correlated with each other. Vitamin D may not be the lone mediator of the therapeutic effects of NBUVB on psoriasis.