Intraepidermal accumulation of polymorphonuclear leukocytes in chronic stable plaque psoriasis

The intraepidermal penetration of polymorphonuclear leukocytes is an early event in the pathogenesis of psoriasis. In the present study we quantified these cells in biopsies from lesional epidermis of chronic stable plaque psoriasis. In this phase intraepidermal penetration of polymorphonuclear leukocytes was shown in 41% of the lesions. Micropustules of Kogoj were seen in 10% of the lesions. Pronounced parakeratosis was associated with the presence of polymorphonuclear leukocytes. Microabscesses of Munro were located exclusively within areas of parakeratosis. The absence of polymorphonuclear leukocytes in the majority of skin biopsies from chronic stable plaque psoriasis is compatible with the cyclic pattern of the exocytosis of these cells.