Pigmented lesions as a sign of photodamage.

Chronic exposure to ultraviolet (UV) radiation causes skin changes, known as photodamage. Apart from damage to the connective tissue of the dermis and to keratinocytes, pigmented lesions, known as 'age spots', occur. There are several types, but the most common lesions are the senile lentigines. The main differential diagnoses include reticular seborrhoeic keratosis and lentigo maligna, and histopathological examination is required for exact differentiation. Variants of lentigo senilis with acute onset after intense UV radiation are sunburn freckles. Psoralens- and UVA-induced freckles, and lentigines occur after phototherapy with artificial UV sources or use of sunbeds for cosmetic tanning. Ephelids are common genetically determined pigment spots appearing during childhood in a distinct photodistribution. Exposure to UV radiation also seems to play a role in the manifestation of acquired nevi. Since pigmented lesions in sun-damaged skin represent more than one entity, they differ in their response to treatment. This should be taken into account when the efficacy of topical therapy is evaluated.