title: [Study on the risk factors of psoriasis].
abstract: OBJECTIVE
  To investigate psoriasis patients with family history and non-family history on their age and season of onset, disease severity and predisposing factors.
  
  
  METHODS
  Two hundred and twenty psoriasis patients with family history and 547 psoriasis patients without, together with 647 normal controls have been investigated through questionnaires. EPI info 6.0 method was applied for data analysis.
  
  
  RESULTS
  (1) In 220 psoriasis patients with family histories, morbidity rates of the first and second-degree relatives were 16.98% and 2.7% respectively. (2) Both mean age and age of onset were younger in females than that in males with family histories (t = 1.715 0, P < 0.05). The mean age of onset was younger in males with family histories than those without. However, there was no significant difference found in females (t = 0.739 2, P > 0.05). The mean age of onset seemed to be younger in females with family histories than that without, but with no significant statistical difference. (3) There were no significant differences in the age and season of onset, disease severity, and predisposing factors between groups with family histories and without. However, environment factors seemed to influence not only psoriasis patients with family histories but also those without, which showed significant difference (chi(2) = 0.23, P < 0.05).
  
  
  CONCLUSIONS
  There was no significant difference in the following aspects as season of onset, disease severity and predisposing factors between the ones with family history and those without, except the age of onset and age of average. The results showed that genetic factor might play an important role in psoriasis patients with family history. It also demonstrated that psoriasis is a multifactor hereditary disease.
authors.affiliation: Department of Dermatology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, China.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Yang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000428:Alcohol Drinking / Q000009:adverse effects; D002648:Child; D004777:Environment; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011565:Psoriasis / Q000209:etiology* / Q000235:genetics; D012307:Risk Factors; D012621:Seasons; D012737:Sex Factors