Psoriasis is a systemic chronic skin disorder characterized by excessive keratinocytes proliferation that results into thickened scaly plaques, itching and inflammatory changes in the epidermis and dermis. It is transmitted genetically but can be provoked by environmental factors.
It is found in approximately 2% of the population that primarily affects the skin and joints.
It is associated with other inflammatory disorders and autoimmune diseases (eg psoriatic arthritis, inflammatory bowel disease, coronary artery disease).
Generally, it begins as red scaling papules that coalesce to form round-to-oval plaques. The rashes are often pruritic and may be painful.


  • Bimodal age of onset: 16-22 years and 57-60 years
  • Environmental or pharmacological impact on lesions
    • Infections, particularly streptococcal, can precipitate or exacerbate the disease
    • Drugs (eg Lithium, antimalarials, alcohol, NSAIDs, beta-blockers) may aggravate the disease 
  • Past medical (eg heart failure, demyelinating disease, inflammatory bowel disease, malignancy) and surgical history
  • Review of family, social and symptomatology history

Physical Examination

  • Diagnosis can usually be made from clinical appearance of the skin lesions
  • Inspect all areas of the body especially extensor surfaces, trunk, perineum, scalp, nails, joints

Laboratory Tests

  • May be necessary for complicated or atypical disease
  • There are no serologic markers or pathognomonic lab tests for psoriasis
  • Skin biopsy, serologic studies for syphilis, bacterial culture, human leukocyte antigen (HLA) typing, microscopic (potassium hydroxide) exams, may be used to differentiate psoriasis from other conditions


Severity of Disease

  • Defined by subjective and objective qualitative assessment based on BSA involvement, location, severity and number of lesions, response to topical treatments, associated physical disability, presence or absence of psoriatic arthritis, psychosocial effects and impact on the quality of life of the patient
  • Assessment of severity may also be done using Psoriasis Area and Severity Index (PASI), Physician’s Global Assessment (PSA), Patient’s Global Assessment (PSA), or Dermatology Life Quality Index (DLQI)
  • BSA
    • <3%: Mild
    • >3% but <10%: Moderate
    • >10%: Severe 
  • Assess quality of life using the following:
    • Coping strategies
    • Daily activities
    • Presence of distress
    • Impact of disease on relationships
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