How effective is ultraviolet (UV) radiation in the treatment of psoriasis?

Updated: Mar 17, 2021
  • Author: Jacquiline Habashy, DO, MSc; Chief Editor: William D James, MD  more...
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Answer

Solar or therapeutic ultraviolet (UV) radiation may be helpful. Various UV light treatments are used—now most commonly, UVB, although psoralen + UVB (PUVA) is still used. Among phototherapy options, Section 5 (2010) of the AAD guideline gives the highest recommendation to oral PUVA or a combination of PUVA and topical agents. [41]

Psoralen is a photosensitizer that is ingested prior to light exposure. PUVA treatment results in conjunctival hyperemia and dry eye, particularly if sun protection is not used. With proper eye protection, there does not appear to be a risk of cataract. Psoralens for either topical (bath) or systemic use may occasionally be difficult to obtain because of intermittent availability issues.

According to the AAD guidelines, PUVA can result in long remissions, but long-term use of PUVA in Caucasians may increase the risk of squamous cell carcinoma (SCC) and possibly malignant melanoma. [39, 41] A prospective study of 1380 patients found a strong correlation between number of PUVA treatments and risk of developing one or more SCC. According to the study, exposure to more than 350 PUVA treatments greatly increases the risk of SCC. [44]

In a retrospective study of 48 patients (mean age, 51 yr; 33 women, 15 men), psoralen-UVA (PUVA) therapy was found to be an appropriate treatment alternative for palmoplantar psoriasis, according to Carrascosa et al. It provided similar response rates to systemic treatment and often with increased tolerance and safety. PUVA was found to be effective in 63% of cases of palmoplantar psoriasis. Systemic therapy, however, was required in 47.9% of patients, with acitretin being the drug most often used. Adverse events occurred in 25% of patients, with the most common one being mild erythema (18%). [45]

Narrowband UVB therapy has always been accepted as a good treatment modality of psoriasis, [46] and the AAD guidelines recommend it over broad-band (UVB), although both are less effective than PUVA. [39, 41] As with PUVA, the guidelines also recommend treatment with combinations of UVB and topical or systemic agents. [41] However, a study by Keaney and Kirsner gives objective reasoning for the benefit of narrowband UV therapy by showing decreases in T cells, dendritic cells, and interleukins within responsive psoriatic plaques compared with plaques that did not respond to therapy. [10] UVB also has the advantage of not leaving the patient with a prolonged period of photosensitivity as PUVA does.

Guttate psoriasis may prove especially responsive to phototherapy. Therapies such as UVB and PUVA have low efficacy for the treatment of nail psoriasis because of the blockage of the UV radiation by the intervening nail plate, so that systemic therapy or intralesional steroids may be best for these. [47]  In 2017, the US Food and Drug Administration (FDA) approved the addition of moderate-to-severe fingernail psoriasis data to the adalimumab prescribing information, based on results from a phase 3, multicenter, randomized, double-blind, parallel-arm, placebo-controlled clinical trial. [48]


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