A Comparison of NB-UVB and PUVA in the Treatment of Vitiligo

Vitiligo is an acquired, progressive depigmenting disorder of the skin and mucous membranes in which melanocytes in affected skin are selectively destroyed. Theories regarding the mechanism of melanocyte destruction include autoimmune, cytotoxic, oxidative, and neural mechanisms. Vitiligo affects 0.5-2% of the world's population and the usual age of onset is in the third decade of life. Photochemotherapy, along with phototherapy and topical therapy, are the most commonly utilized and effective vitiligo treatment modalities. Photochemotherapy for the treatment of vitiligo was historically used in ancient India and Egypt, where Hindus and Egyptians applied psoralen-containing plant extracts to depigmented vitiligo lesions where were then exposed to sunlight. These plants were found to be Ammi majus and Psoralen corylefolia, which contain 8-methoxypsoralen (8-MOP) and 5-methoxypsoralen (5-MOP). Phototherapy has been shown in many studies to induce effective repigmentation in more than 70% of patients with early and/or localized disease. Narrow-band ultraviolet B radiation (NB-UVB) with an emission spectrum of 310-312 nanometers (nm) is a safe treatment modality that is often used two to three times weekly as monotherapy, or combined with topical steroids. The treatment is safe in children, pregnant women and lactating mothers, and has minimal adverse effects (xerosis, pruritus, skin aging, and tanning). The risk of skin cancer is minimal even with multiple treatments although there is a greater risk of phototoxicity with depigmented skin. NB-UVB has also been used in combination with antioxidants such as vitamin E. Photochemotherapy involves the usage of psoralens combined with natural sunlight or UV light, usually ultraviolet A radiation (PUVA). 8-MOP or 5-MOP can be applied topically or used orally, followed by light exposure. Psoralens may not be used in pregnancy and there is a need for photoprotection following their use; there is as well a higher risk of burns, eye injury, and cutaneous malignancy than NB-UVB that may limit their cumulative usage. A 10-year retrospective study showed that PUVA is only moderately effective in widespread vitiligo (Kwok et al, 2002). Another small study from India successfully combined PUVA with a keratinocyte-melanocyte graft technique for stable vitiligo (Kachhawa et al, 2008).