Abstract: Objective To investigate the effects of genetic factors on the onset of psoriasis. Methods Seven hundred and twenty patients with psoriasis vulgaris were studied by questionnaire. Results ① For the male and female patients, the peak ages of the first onset were 20～ 29 and 10～ 19 years, respectively, and the average ages were 27.57±12.18 and 23.01±12.40 years, respectively.② In 720 psoriatics, 212 cases (29.4%) reported to have a family history of psoriasis. The age of onset was earlier in man with family history than that in man without family history (P<0.01),but the female patients did not; the age of onset was earlier in psoriatics whose fathers and/or mothers suffering from psoriasis than that in psoriatics with normal parents (P<0.05).③ The number of cases with typeⅠ psoriasis (early onset, age of the first onset< 40)was 633(87.9%),and that with typeⅡ (late onset, age of the first onset≥ 40) was 87(12.1%). The morbidities of first degree relatives were 5.77% in typeⅠ psoriatics and 3.45% in typeⅡ (P<0.01), and those of second degree relatives were 0.94% in typeⅠ psoriatics and 0.19% in typeⅡ (P<0.01).The onset of psoriasis was earlier in the females than that in the males in typeⅠ psoriasis (P<0.01), but it was not the same in typeⅡ (P>0.05).④ The heritabilities of psoriasis were 71.07%± 2.05% in first degree relatives and 36.77%±5.17% in second degree relatives. Conclusion The results show that psoriasis vulgaris may be a multigenic inheritable disease, and the genetic factors play an important role in the pathogenesis.

Key words: Psoriasis, Prevalence, Hereditary diseases