Immunohistochemical study of the early histopathologic changes occurring in trauma-injured skin of psoriatic patients.

In the present study we have investigated the early histopathologic as changes occurring in the Koebner reaction induced by traumatic injury in uninvolved skin of 23 psoriatic and 7 non-psoriatic control patients. A punch biopsy of the injured area was performed after 2-3 (15 cases) or 7 days (8 cases). As a trauma, instead of the classic sellotape stripping, needle scarification was used. A peculiar histological feature of the skin biopsies of 13/23 psoriatic patients (56%) was a keratinocyte hyperplasia leading to a "papillary" projection into the upper dermis, just beneath the scarification. The papillary projection was associated with the expression of intercellular adhesion molecule-1 (ICAM-1) in the keratinocytes of 9/13 cases (70%) and with the presence of peri-papillary aggregates of CD68+ cells in 10/13 cases. In the upper dermis, tenascin was markedly expressed in 12/13 cases. Moreover, in one third of the cases, just beneath the scarification, there was reabsorption of the epidermal basal membrane as documented by a marked reduction of collagen type IV and laminin content. These histopathological alterations were detected in 6/15 psoriatic patients whose skin biopsy was taken 2-3 days after scarification, in 7/8 after 7 days, and in only 1/7 non psoriatic controls. Our results indicate that needle scarification can be a suitable method to study the early events occurring in trauma injured psoriatic skin.