hyperplasia

Light microscopic image of the lesion showing hyperkeratosis on the surface, thickening of the granular layer, and marked psoriasiform hyperplasia (hematoxylin-eosin staining, x40).

A skin biopsy showed only mild psoriasiform hyperplasia, occasional dermal eosinophils, and no neutrophils.

Histopathology of the lesion revealed psoriasiform hyperplasia, hyperkeratosis, parakeratosis, spongiosis and few necrotic keratinocytes in upper epidermis.

The histopathological findings are parakeratosis and psoriasiform hyperplasia with neutrophilic infiltration into the epithelium.

IL-22 is another key downstream cytokine in the IL-23/Th17 axis, being upregulated in psoriatic skin as compared to normal skin [5, 29, 40, 41]; IL22 mediates keratinocyte hyperplasia via STAT3 activation, leading to psoriasiform hyperplasia. In the absence of IL22, severity of both IL-23-mediated and imiquimod-induced psoriasis-like dermatitis in corresponding mouse models is markedly reduced [40,42, 43].