Systematic review of the prevalence and incidence of the photodermatoses with meta-analysis of the prevalence of polymorphic light eruption.

Information about the prevalence of photodermatoses is lacking, despite their substantial impact on life quality. Our objective was to systematically review the literature to establish what is known regarding prevalence and incidence of photodermatoses. We searched Medline, CINAHL and Embase from inception to 2021 to identify original population-based studies in English literature reporting the prevalence and/or incidence of photodermatoses. Information was extracted according to geographical location and risk of bias was assessed using a 10-point risk of bias tool for prevalence studies. Primary outcome was the population prevalence of photodermatoses. Prevalence data for polymorphic light eruption (PLE) were used to calculate the global pooled prevalence of PLE. Twenty-six studies were included; 15 reported prevalence of photodermatoses based on samples of the general population and 11 on prevalence and/or incidence from national and international registry data. The general population studies involved PLE (nine studies), unspecified photosensitivity (2), actinic prurigo (2), juvenile spring eruption (1), chronic actinic dermatitis (1) and variegate porphyria (1), while registry studies reported on cutaneous porphyrias and genophotodermatoses (nine and two studies, respectively). Worldwide the prevalence of PLE between countries ranged from 0.65% (China) to 21.4% (Ireland). The pooled estimated prevalence of PLE was 10% (95% CI 6%-15%) among the general population (n = 19,287), and PLE prevalence increased with distance from the equator (r = 0.78, p < 0.001). While several photodermatoses are rare, photosensitivity can be prevalent at wide-ranging world locations, including Egypt where photosensitivity was found in 4% of children and 10% of adults. This study showed that PLE is highly prevalent in many populations and that its prevalence shows a highly significant correlation with increasing northerly or southerly latitude. Available population-based studies for photodermatoses suggest they can be prevalent at a range of world locations; more attention is required to this area.