| Alopecia areata (AA) is hypothesized to be an organ-specific autoimmune disease with genetic predisposition and an environmental trigger. Etiological factors have not yet been definite at present. Approximately 2% of the population is at a lifetime risk of suffering from AA, which occurs worldwide. Approximately 5% of cases, the disease progresses to AT/AU. AA affects approximately 4.6 million individuals in the United States alone. There have not a large national investigation about AA in China yet. There were lots of theories of etiology with regard to AA, such as heredity, emotion hyperirritability, endocrine maladjustment and obstacle of immunological function and so on is possibly important induced factors. As for its genetic model, it has not been definitely concluded at present. The purpose of this study is to explore the effects of genetic and environmental factors on the onset of AA and presume the possible genetic model of AA.1032 patients with AA were studied by questionnaire and follow-up. The complex segregation analysis and heritability was performed, with the aid of Falconer's method, Epi info 6.0 software, SPSS software and SAGE-REGTL program. The results showed that ?A peak age of onset was seen between 20 and 40 years for both male and female. The age of onset ranged from 1 to 74 years (mean 28.98 13.43 years).For the male and female patients, the peak ages of the first onset were 29.46 0.60 and 28.47 0.58 years, respectively. The difference was not significant in the t-test (y=1.184, p>0.05).(2)A positive family history of AA was obtained in 87 patients (8.4%). 852 (82.6%) patients experienced their first episode of AA within the first four decades of life.(3)A greater severity and longer duration of AA were seen in early onset group (age of onset <=30 years) man in late onset group (age of theonset >0 years). The early onset group has more affected first- and second-degree relatives than the late onset group. The difference of the prevalence rates of first- and second-degree relatives in the two groups of AA patients is significant (x2=6.808 and 8.910 respectively, p<0.01).(4)It could be found that the prevalence rate of first-degree relatives (1.60%) was higher than that of second-degree relatives (0.19%) and third-degree relatives (0.03%). The difference is significant (x2=116.64 and 19.832 respectively, p<0.001). The difference of the prevalence rates of first- and second-degree relatives between probands and controls are significant (x2=98.198 and 15.043 respectively, p<0.001). This indicates a clear hereditary tendency in AA.(5)Mendelian, No-major-gene and Environment modeles were rejected by complex segregation analysis. (6)According to Falconer's method, we obtained heritability (h2) of AA in first- second- and third-degree relatives of probands were 47.16% 2.79%, 42.53% 7.36% and 22.29% 21.63% respectively, and the average heritability was 46.23% 0.07%. (7)Seven environmental factors were related with AA with multivariate unconditional logistic regression model, in which spinsterhood (OR=0.780) was a protective factor for AA and psychological stress (OR=8.957), dumps,anxiety (OR=2.543), insomnia (OR=15.844), enjoy eating pungent food (OR=2.661), dye hair history (OR=2.767) and tire excessively (OR=4.688) were risk factors for AA. Conclusion: It suggests that AA follows a pattern of polygenetic or multifactorial inheritance, the genetic factors and environmental factors play roles interactionally in the pathogenesis.
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