Background: Porokeratosis is a dyskeratotic disorder of the skin characterized by cornoid lamella with parakeratosis, hyperkeratosis and loss of granular layers. The pathogenesis of porokeratosis and the mechanism(s) of its abnormal keratinization are still unknown.
Objective: To elucidate the mechanism(s) of abnormal keratinization that leads to the formation of cornoid lamellae in porokeratosis.
Methods: Apoptosis of keratinocytes was assessed in the skin of seven patients by an in situ apoptosis assay based on the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) reaction. Patterns of loricrin and involucrin expression were examined by immunohistochemistry.
Results: TUNEL-positive keratinocytes were observed in the epidermis underlying the cornoid lamella in all cases examined. Furthermore, loricrin expression was interrupted there, in contrast to involucrin, which was expressed diffusely in the lesional epidermis.
Conclusions: These results suggest that an abnormal early keratinocyte apoptosis accompanied by dysregulation of terminal differentiation of those cells may be involved in the pathogenesis of porokeratosis.