Disseminated superficial porokeratosis: what is the association with ultraviolet radiation?

A female patient is presented who consistently developed lesions of disseminated superficial porokeratosis (DSP) whilst on holiday abroad. The lesions resolved completely within 4-6 weeks of return to the UK. Induction of the lesions by exposure to artificial sources of UVA and UVB was unsuccessful. Disseminated superficial porokeratosis (DSP) is thought to be a clonal disorder of keratinization and the histological hallmark is the cornoid lamella. The aetiology of DSP is unclear although it has been suggested that local or systemic immune suppression may allow the development of mutant clones of keratinocytes. Chernosky and Freeman first proposed an actinic aetiology for DSP in 1967 but the mechanism of induction is unclear.