RESUMO
Objective To describe the genetic epidemiologic features of alopecia areata (AA) patients in China and to presume the possible genetic mo del of AA.Methods A case-controlled study of 1032 AA patients was performed to analyze the effect of genetic factors on the liability to AA.Complex segreg ation and heritability analysis were performed using Falconer's method and SAGE-REGTL programs.Results The mean age of onset was 28.98 ? 13.43 years.The d ifference in the mean age of onset was not significant between males and females.A total of 82.6 percent of patients experienced their first episode of AA befo re the fourth decades of life.A positive family history of AA was obtained in 8 7 patients (8.43%).The prevalences of AA were 1.58%,0.19% and 0.03% in the firs t-,second-and third-degree relatives of the probands respectively,which were significantly higher than those in the controls(P