aetiology of psoriasis

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)

Reference:

• 1. Schön M.P, Boehncke W.H. Psoriasis. NEJM 2005;352:1899-1912
• 2. Guillen S, Khachemaoune A. Photo quiz - Large, Silvery Plaques. AFP 2007;75(8)

Last edited 08/2019