ROLE OF SUM EXPOSURE ON NEVUS - FIRST STU DY IN AGE, SEX AND PHENOTYPE CONTROLLED POPULATIONS

Background. These studies were designed to assess the influence of sun exposure on nevi in white people. In order to eliminate the confoundi ng effect of age, sex and phenotype, two parallel studies were conduct ed in people of the same age (17 to 24 years), sex (males) and phenoty pe: one in people with ''red'' phenotype and one in people with ''dark '' phenotype. Results. In both groups, comparison of nevus counts on t he inner and outer side of the upper extremities and comparison of mea n density of nevi (number per square meter) in always-exposed and neve r-exposed skin show that number of nevi is higher in sun exposed areas . In both groups the density of large and atypical nevi was maximal on intermittently sun-exposed skin while the density of small nevi was m aximal on always-exposed skin. The number of large nevi on intermitten tly-exposed skin correlated with cumulative intensive exposure during beach recreation in the red phenotype group. The number of large nevi was significantly higher in red phenotypes who repeatedly experienced severe sunburns in their first 20 years of life. Conclusions. The numb er of nevi at the end of the second decade is influenced by cumulative sun exposure from birth. ''Traumatizing'' sun exposure, which is more frequent in ''red'' phenotype than in ''dark'' one, has an influence on the number of large nevi and is therefore likely to make small nevi grow.