Background: Although dysplastic nevi are an important risk factor for melanoma, little is understood about the epidemiology of these nevi. To further characterize some of the correlates of dysplastic nevi, we reexamined patients from one of the original prevalence reports and their first-degree relatives.
Objective: Our purpose was to characterize the prevalence and correlates of dysplastic nevi.
Methods: We studied 25 persons originally diagnosed with dysplastic nevi in 1980 and 1981, 28 controls stratified by age, sex, race, and date of initial examination, and all willing first-degree relatives of both patients (n = 78) and control subjects (n = 76). Each study subject underwent a full skin examination and biopsy of nevi suspected of being dysplastic nevi, if willing.
Results: Eighty percent of the case kindreds were multiplex (2 members or more affected) for dysplastic nevi; the relative risk of having dysplastic nevi was 7.2 (95% confidence interval 2.1 to 24) if one or more relatives had dysplastic nevi. Three of the cases (12%) in multiplex families also had a first-degree relative with melanoma. Cases and relatives with dysplastic nevi of both patients and control subjects tended to have increased numbers of nevi. The risk of having dysplastic nevi rose 99-fold in persons with more than five nevi 4 mm or larger and/or scars on their back (p < 0.001).
Conclusion: These data support the hypothesis that family members of unselected persons with dysplastic nevi are likely to have dysplastic nevi and may be at increased risk of melanoma.