Prevalence of melanocytic nevi and freckles in young Israeli males. Correlation with melanoma incidence in Jewish migrants: demographic and host factors.

The role of host and environmental factors in the pathogenesis of multiple melanocytic nevi, atypical nevi, and freckles was studied in 1989 in a random sample of 3,040 Israeli males aged 17 years. Multiple melanocytic nevi were significantly associated with family history of melanoma or multiple melanocytic nevi (odds ratio (OR) = 15.0), fair or lightly pigmented skin color (OR = 2.7 and 2.3, respectively), and affiliation to the high or heterogenous melanoma risk group, determined by the incidence rates of melanoma in Jewish migrants from corresponding origin (OR = 3.1 and 2.1, respectively). An environment-related effect may account for the increased multiple melanocytic nevi risk among second- (OR = 8.2) compared with first-generation, native-born recruits (OR = 3.0) from the high melanoma risk group whose families had been living in Israel the longest. Atypical nevi were associated with fair (OR = 6.1) and lightly pigmented (OR = 3.5) skin color, high and moderate sunburn susceptibility (OR = 4.7 and 2.5, respectively), and family history of melanoma or multiple melanocytic nevi (OR = 4.7). Freckles were significantly associated with sun-sensitive phenotype, family history of melanoma or multiple melanocytic nevi (OR = 1.5). Conservative (OR = 1.9) or nonreligious status (OR = 1.9), and high (OR = 2.4) or heterogenous melanoma risk groups (OR = 1.8). These findings indicate that environmental factors may modify the occurrence of multiple melanocytic nevi and freckles in genetically susceptible ethnic groups.