[Study on genetic epidemiology on 815 patients with vitiligo in Zhejiang area]

Genetic factors are thought to be involved in the development of vitiligo. The aim of this study is to explore the possible genetic model of vitiligo by analyzing the genetic characteristics of 815 patients from Zhejiang province.

Data for 815 patients with vitiligo together with their first- and second-degree relatives were obtained using a standardized questionnaire. All these information was requested to confirm the answers about family history in order to reduce the possibility of 'recall' bias. The 815 probands would include 411 (50.43%) males and 404 (49.57%) females with a varied age from 2 months to 71 years old. Since the information on general prevalence of vitiligo in this area was absent, a control group was set up to facilitate the calculations of heritability degree. 468 persons of the control group were from non-vitiligo population with a sex ratio of 241(male): 227(female) with varied age of 4 months to 80 years old. Both gender and age were comparable between the vitiligo and the control population. The inheritance pattern estimation, heritability calculation and complex segregation analysis were performed with Penrose method, Falconer regression method and SAGE-REGTL program.

In 815 vitiligo probands, 128 had and 687 had not family histories, with a heritability rate of 15.7%. The vitiligo prevalence in proband's first degree relatives was 2.580%, higher than the prevalence of 0.618% in second degree relatives, and both of them were higher than general prevalence: 0.192%. By Penrose method, the rates on different catagories were as follows: sibling prevalence rates s = 0.080 18; population prevalence rate q = 0.001 92; s/q = 41.76. The ratio of s/q did not approach 1/2q (260.42) or 1/4q (130.21), but approached 1/square root of q(22.82), suggesting vitiligo was consistent with a mode of polygenic inheritance. Using Falconer's method, heritabilities of vitiligo in first-and second degree relatives of probands were 59.61% (95% confidence interval 65.37-53.84) and 55.20% (95% confidence interval 43.88-66.52), respectively. The weighted average of heritability in all relatives was 58.7% (95% confidence interval 53.56-63.83). The results of complex segregation analysis suggested that major gene model including the Mendelian dominant, recessive and additive hypotheses were not rejected (P > 0.05). Purely environmental model and no transmission model were rejected at a 0. 001 significance level. According to AIC, Mendelian dominant inheritance was the best-fitted hypothesis.

Genetic factors played an important role in the occurrence of vitiligo, and the genetic model of vitiligo could serve as the polygenetic or multifactorial inheritance with major gene trait.