Psoriasis: Causes

Pathogenesis (disease development)

Psoriasis is a multifactorial disease in which genetic factors and exogenous factors (infections, smoking/passive smoking, use of certain medications) interact in the pathogenesis. For children with their typical exanthematous psoriasis, especially streptococcal infections (hemolytic streptococci of groups A, C, and G) are a classic trigger factor.

Psoriasis is considered a systemic autoimmune disease (disease in which the immune system is directed against the body’s own structures), in which the endogenous T cells (cells belonging to the lymphocyte cell group) are activated by autoantigens. Subsequently, there are accumulations of leukocytes (white blood cells), which in turn affect the keratinocytes (horn-forming cells). There is an excessive acceleration of proliferation (rapid growth of tissue) (→ acanthosis (thickening of the epidermis) and parakeratosis/dysfunctional keratinization).

Tumor necrosis factor (TNF) plays a central role in the inflammatory process of psoriasis.

Etiology (causes)

Biographic causes

  • Genetic burden from parents, grandparents (polygenic disease; genetic contribution to psoriasis risk is approximately 60-70%)
    • Genes/SNPs (single nucleotide polymorphism):
      • SNP: rs1265181 in an intergenic region.
        • Allele constellation: CT (5.0-fold).
        • Allele constellation: TT (22.6-fold)

The following factors/causes can trigger psoriasis if a genetic predisposition is present at the same time:

Biographical causes

  • Hormonal factors – menarche (beginning of the first menstrual period), menopause (menopause in women).

Behavioral causes

  • Nutrition
    • High intake of the omega-6 fatty acid arachidonic acid (animal foods, especially pork and pork products and tuna).
    • Weight gain
  • Consumption of stimulants
  • Psycho-social situation
    • Psychological stress
  • Chemical skin irritation
  • Mechanical skin irritation
  • Thermal skin irritation such as sunburn
  • Excess weight (BMI ≥ 25; obesity)

Disease-related causes

  • Infections with streptococci
  • Hypertension (high blood pressure)
  • Injuries to the skin
  • Skin inflammations

Medication

  • ACE inhibitors
  • Beta-blockers – medications used to treat hypertension (high blood pressure); women who took beta-blockers regularly for six years or more had a 39% increased risk of developing psoriasis compared with women who did not take beta-blockers
  • Chloroquine – drug used to treat malaria.
  • Interferon – drug that has an immunostimulatory, especially antiviral and antitumor effect.
  • Lithium – drug for the treatment of mental illness
  • Tetracycline (antibiotic)
  • U. v. m.

Other causes

  • Pregnancy
  • Breastfeeding