WEDNESDAY, May 7, 2025 (HealthDay News) -- The mutation burden in normal skin is higher in patients with psoriasis due to narrow-band ultraviolet B (NB-UVB) phototherapy, according to a study published online May 3 in the British Journal of Dermatology.

Joanna C. Fowler, from the Wellcome Sanger Institute in Cambridge, England, and colleagues estimated the total number of NB-UVB exposures whereupon skin cancer surveillance should commence by determining the mutation burden resulting from an NB-UVB treatment. Biopsies of normal skin from 16 patients with psoriasis were obtained before and after a course of NB-UVB. To determine the mutational signatures and mutation burden, epidermal DNA was sequenced using nanorate sequencing (NanoSeq).

The researchers found that the number of mutations in skin increased with the NB-UVB course. The median increase in mutation burden was 0.55 and 0.89 substitutions/Mb in infrequently sun-exposed (buttocks) and frequently sun-exposed (forearm) skin, respectively. There was variation seen in the change in mutation burden due to NB-UVB, from 1.16- to 10.5-fold in buttock skin and from 0.93- to 2.33-fold in forearm skin, with the increase mainly due to ultraviolet radiation exposure-linked mutational signatures SBS7a and SBS7b. Skin cancer surveillance should be offered at 422, 165, and 58 NB-UVB exposures for those receiving low, typical, and high levels of sun exposure, respectively, for patients with minimal erythema dose (MED) equal to two standard erythemal doses.

"Our findings demonstrate the feasibility of employing NanoSeq to determine mutation burden from a NB-UVB course and provide a rationale for personalizing skin cancer surveillance for patients receiving NB-UVB according to their MED and exposure to natural sunlight," the authors write.

One author disclosed ties to Almirall.

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