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Aetiology of psoriasis

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The aetiology of psoriasis seems to be multifactorial:

  • genetic:
    • about 30% of patients having one first degree relative with psoriasis themselves develop the disease; for patients having two infected first degree relatives, the figure is about 60%
    • there are strong HLA associations (HLA CW6)
      • note - environmental factors are important - monozygous twin studies show a concordance rate of only 40 to 65%

  • infection:
    • Streptococcal pharyngitis (1) - may cause guttate psoriasis, usually in children and young adults, and within 10-14 days; this pattern is associated with HLA-Cw6 in about 75% of cases
    • AIDS/HIV (1)
    • skin lesions identical to psoriasis may arise in patients with Reiter's syndrome

  • stress, e.g. moving house; examinations

  • trauma:
    • Koebner phenomenon - skin disease occuring in scars or sites of trauma - well recognised in psoriasis (1)

  • drugs:
    • alcohol
    • beta blockers
    • non-steroidal anti-inflammatory drugs
    • antimalarials, e.g. chloroquine
    • mepacrine
    • Lithium (1)

  • Some treatment methods of psoriasis (e.g., anthralin and phototherapy) - if treated with high initial doses (1)

  • Smoking and alcohol (2)


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