Major gene segregation of actinic prurigo among north American Indians in Saskatchewan

Actinic prurigo is an idiopathic, familial photodermatosis seen especially in American Indians, Segregation analysis was performed on 12 Saskatchewan pedigrees with American Indian ancestry, comprising a total of 1,148 indivi duals, ascertained via probands diagnosed with actinic prurigo, Although a high degree of familial aggregation has been noted in the past and dominant inheritance has been suggested, no formal segregation analysis has been at tempted. Actinic prurigo has a variable age of onset and, therefore, age at the time of censoring must be taken into account in the analysis, However, as these ages of 57% of the unaffected individuals were missing, an algori thm was devised to impute the missing ages from known birth years in the fa mily based on the age differences among relatives and spouses. Using these imputed ages, simple dominant inheritance with incomplete penetrance and a single age of onset distribution was found, The method for imputing the age s at examination was evaluated, as was the correction for ascertainment, by using alternative methods and comparing the results, Regardless of the met hod used, a dominant mode of inheritance without any multifactorial compone nt remained the best hypothesis. Am. J. Med, Genet. 92:212-219, 2000, (C) 2 000 Wiley-Liss, Inc.