Psoriasis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]


Psoriasis is an immune-mediated disease with a genetic predisposition, though no specific immunogen has been implicated in the development of psoriasis. The pathophysiology of psoriasis consists of interactions between cytokines, dendritic cells, and T lymphocytes (particularly Th1 and Th17).[1] Common triggers of psoriasis include injury to the skin, trauma, infection, and medications. T cells play a key role in the pathogenesis of psoriasis via the production of pro-inflammatory cytokines. Certain genes increase the likelihood of developing psoriasis; the first gene that was discovered to be linked to the development of psoriasis was HLA-Cw6, which is located at PSORS1 at chromosomal position 6p21.3. Microscopically, skin affected by psoriasis displays parakeratosis, acanthosis, hyperkeratosis, Kogoj pustules, and Munro's microabscesses. The red appearance of psoriatic lesions is due to dilated blood vessels in the skin.


There are two main hypotheses about the development of psoriasis. The first hypothesis considers psoriasis as primarily a disorder of excessive growth and reproduction of skin cells, in which psoriasis is a manifestation of a fault of the epidermis and its keratinocytes. The second hypothesis views the disease as an immune-mediated disorder in which the excessive reproduction of skin cells is secondary to factors produced by the immune system. T cells (which normally help protect the body against infection) become active, migrate to the dermis, and trigger the release of cytokines (tumor necrosis factor-alpha [TNFα] in particular), which cause inflammation and the rapid production of skin cells. It is not known what initiates the activation of the T cells.


Cutaneous psoriasis

The immune-mediated nature of psoriasis has been demonstrated by multiple studies in which various treatments that target and inhibit the proliferation and activation of T cells have been used successfully.[2][3][4]


Role of Dendritic Cells

Role of T Cells

NF-κB Pathway

Psoriatic arthritis

The pathogenesis of psoriatic arthritis (PsA) involves the following events:[13]

Osteoclast mediated joint destruction


Pathogenesis of psoriasis

Associated conditions

Psoriasis is associated with the following conditions:[23][24][25][26][27][28][29][30][31][32][33][34]

Gross pathology

  • On gross inspection, psoriatic lesions have the following characteristics:
  • The surface area of the body affected by psoriasis can be measured roughly as a percentage of body area using the palm to represent 1% of the body. One-third of patients present with at least 10 percent body involvement, which is referred to as moderate-to-severe psoriasis.
Psoriasis gross examination, courtesy of

Microscopic pathology

Cutaneous psoriasis

Psoriasis microscopic pathology, courtesy

Psoriatic arthritis


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