The genetic epidemiology of psoriasis vulgaris in Chinese Han.

BACKGROUND

The aim of this study was to explore the effects of genetic factors on the onset of psoriasis vulgaris and to develop a possible genetic model of psoriasis in Chinese Han.

METHODS

Data for 1043 patients with psoriasis vulgaris were obtained by questionnaire. Complex segregation analysis and heritability were performed using Penrose's method, Falconer's method, and the EPI INFO 6.0 and SAGE-REGTL programs.

RESULTS

(1) For male and female patients, the peak ages of initial onset were 30-39 and 10-19 years, respectively, with the mean age of initial onset being 27.69 +/- 12.32 years in males and 23.26 +/- 12.56 years in females. (2) Of 1043 patients with psoriasis, 326 (31.26%) were reported to have a family history of psoriasis. The onset for males with a family history of psoriasis was earlier than that for those without a family history (P < 0.01). The morbidities of first-degree relatives were 7.67% in patients with type I psoriasis and 5.27% in patients with type II (P < 0.01), and those of second-degree relatives were 1.04% in type I and 0.24% in type II (P < 0.01). (3) The onset of psoriasis was earlier in females than in males in type I psoriasis (P < 0.01), but this was not the case in type II (P > 0.05). (4) The prevalence of psoriasis in first- and second-degree relatives of the proband with psoriasis was 7.24 and 0.95%, respectively; higher than that in the general population (0.146%). (5) The heritability of psoriasis in first- and second-degree relatives was 67.04 and 46.59%, respectively. The Mendelian, no-major-gene and environment model was rejected by complex segregation analysis.

CONCLUSION

Psoriasis vulgaris follows a pattern of polygenetic or multifactorial inheritance rather than single-gene inheritance.