What is the pathogenesis of psoriasis?

Updated: Nov 20, 2020
  • Author: Jacquiline Habashy, DO, MSc; Chief Editor: William D James, MD  more...
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Answer

The pathogenesis of this disease is not completely understood. Multiple theories exist regarding triggers of the disease process including an infectious episode, traumatic insult, and stressful life event. In many patients, no obvious trigger exists at all. However, once triggered, there appears to be substantial leukocyte recruitment to the dermis and epidermis resulting in the characteristic psoriatic plaques.

Specifically, the epidermis is infiltrated by a large number of activated T cells, which appear to be capable of inducing keratinocyte proliferation. This is supported by histologic examination and immunohistochemical staining of psoriatic plaques revealing large populations of T cells within the psoriasis lesions. One report calculated that a patient with 20% body surface area affected with psoriasis lesions has around 8 billion blood circulating T cells compared with approximately 20 billion T cells located in the dermis and epidermis of psoriasis plaques. [9]

Ultimately, a ramped-up, deregulated inflammatory process ensues with a large production of various cytokines (eg, tumor necrosis factor-α [TNF-α], interferon-gamma, interleukin-12). Many of the clinical features of psoriasis are explained by the large production of such mediators. Interestingly, elevated levels of TNF-α specifically are found to correlate with flares of psoriasis.

One study adds further support that T-cell hyperactivity and the resulting proinflammatory mediators (in this case IL-17/23) play a major role in the pathogenesis of psoriasis. [10]


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