Vitiligo is a common, acquired, autoimmune disorder seen in clinic characterized by the progressive loss of melanocytes leading to depigmented macules and patches.¹ Estimated prevalence rates range from 0.1 to 2% of the global population, and it has been shown to have significant impact on psychosocial function as well as quality-of-life metrics.² Vitiligo can affect any skin surface and is generally classified into 2 subcategories: segmental (occurring in a dermatomal or quasi-dermatomal pattern) and nonsegmental (which may be generalized, universal, acrofacial, or mucosal). Phototherapy has emerged as a safe and effective treatment modality for patients with vitiligo due to its proven efficacy and favorable side effect profile. While several options exist, the best studied, most successful forms of phototherapy for vitiligo include narrowband UVB (NB-UVB) and excimer light/laser. This article provides a high-level overview of these modalities as well as an up-to-date reference of their efficacy, dosing, mechanism, adverse effect profile (Table). 

NARROW BAND UVB (NB-UVB) PHOTOTHERAPY 

NB-UVB phototherapy is characterized by targeted exposure to polychromatic light with a peak emission wavelength between 311 nm³ and 313 nm³. Numerous clinical studies have demonstrated the effectiveness of NB-UVB in repigmenting vitiligo lesions, with success rates ranging from 48% to 64%.^3-5 Common side effects include pruritus, erythema, burning/blisters, xerosis, and darkening/thickening of normal skin.³ While the carcinogenic risk of patients with vitiligo receiving NB-UVB treatment remains incompletely defined, studies have identified no increased risk of skin cancer in patients receiving NB-UVB for psoriasis.^3,6 Also, interestingly, despite the absence of melanin, the development of skin cancers in vitiligo lesions is rare.³ In 2017, the Vitiligo Working Group generated recommendations for NB-UVB use in patients with vitiligo that include optimal frequency of administration (3 times per week), initial dosing (200 mj/cm2), dose adjustments based on degree of erythema and missed doses, special site instructions, complication management, and pre- and post-treatment recommendations.⁴ 

EXCIMER 

Excimer is a newer targeted form of phototherapy characterized by a wavelength of 308nm (UVB) that may be administered using a laser or lamp medium.³ Excimer laser emits a monochromatic wavelength at high irradiance with spot sizes ranging from 15 to 30 mm.⁵ Smaller spot sizes allow selective treatment of vitiligo lesions, reducing risk of perilesional hyperpigmentation. However, small spot size also makes this modality time-consuming and unsuitable for patients with vitiligo involving large body surface areas (>15% TBSA).³ The monochromatic excimer lamp also emits light with a 308-nm wavelength and has been shown to have equivalent efficacy to laser with larger area effect, shorter treatment times, and lower cost.⁵ Several studies have compared the therapeutic efficacy of excimer and NB-UVB in vitiligo and have shown similar overall effectiveness, with excimer demonstrating a more rapid and greater degree of specific lesion repigmentation.⁷ Excimer has also been shown to excel in the treatment of segmental vitiligo when compared with NB-UVB, with studies showing that only 7.7% of patients with segmental vitiligo respond with NB-UVB compared with 42.4% of patients treated with excimer.⁸ Dosing regimens are relatively similar to NB-UVB.⁹ 

COMBINATION THERAPY 

Notably, both NB-UVB and excimer phototherapy have improved repigmentation when combined with other modalities–particularly corticosteroids (oral and topical), topical calcineurin inhibitors, oral antioxidants, dermabrasion with Erbium laser, fractional CO2, and subcutaneous afamelanotide.³ 

In all, as the therapeutic armamentarium for vitiligo expands, phototherapy continues to serve as a safe and effective cornerstone for its management that dermatologists should understand and be able to implement.

Comparison of Efficacy, Side Effects, and Ideal Clinical Scenarios for the Most Common Forms of Phototherapy for Vitiligo

Of note, while other phototherapy modalities have shown a degree of efficacy for vitiligo, including visible light and low-level light therapy (for segmental vitiligo in children with periorbital / perioral lesions) as well as broad-band UVB and broadband UVA, the supportive evidence for these modalities is limited, and safety data largely supports adjunct use in lieu of NB-UVB and excimer.

REFERENCES 

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2. Silverberg JI, Silverberg NB. Quality of life impairment in children and adolescents with vitiligo. Pediatr Dermatol. 2014;31(3):309-318. doi:10.1111/pde.12226 
3. Esmat S, Hegazy RA, Shalaby S, Hu SC, Lan CE. Phototherapy and combination therapies for vitiligo. Dermatol Clin. 2017;35(2):171-192. doi:10.1016/j.det.2016.11.008 
4. Mohammad TF, Al-Jamal M, Hamzavi IH, et al. The Vitiligo Working Group recommendations for narrowband ultraviolet B light phototherapy treatment of vitiligo. J Am Acad Dermatol. 2017;76(5):879-888. doi:10.1016/j.jaad.2016.12.041 
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9. Zhang XY, He YL, Dong J, Xu JZ, Wang J. Clinical efficacy of a 308 nm excimer laser in the treatment of vitiligo. Photodermatol Photoimmunol Photomed. 2010;26(3):138-142. doi:10.1111/j.1600-0781.2010.00509.x 
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