Repeated equally effective suberythemogenic exposures to ultraviolet (UV)A1 or narrowband UVB induce similar changes of the dermoscopic pattern of acquired melanocytic nevi that can be prevented by high-protection UVA-UVB sunscreens.

BACKGROUND: Sunlight modifies the size and the dermoscopic pattern of acquired melanocytic nevi (AMN). OBJECTIVE: We investigated whether repeated exposures to equally effective suberythemogenic doses of ultraviolet (UV)A or UVB can induce changes in the dermoscopic features of AMN. METHODS: Twenty volunteers received equally effective doses of narrowband UVB or UVA1. During exposures, an AMN was covered with an opaque tape, another was shielded with the sunscreen, and another was left unprotected. RESULTS: Nevi exposed to either narrowband UVB and UVA1 showed statistically significant changes in their dermoscopic features: increased size, increase of pigment network, overall color darkening, formation of focal branched streaks, and increased number and size of brown dots and globules. LIMITATIONS: The study is a clinical cohort study on a small number of selected patients. CONCLUSION: AMN show similar changes in size and dermoscopic pattern after narrowband UVB and UVA1 exposures.