Psoriasis pathogenesis


  • Hyperkeratosis – thickening of cornified layer
  • Acanthosis – epidermal thickening (3-5 times normal)
  • Rete ridge elongation (arrowheads)
  • Parakeratosis – retained nuclei in stratum corneum

Other features:

Absent granular layer and infiltration of neutrophils and activated lymphocytes (from dermis to epidermis)

Nail changes (occur in 50% of patients)


  • Subungual hyperkeratosis (proliferation under nail bed)
  • Thickening
  • Onycholysis (separation from the nail bed)
  • Pitting, ridging

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