Psoriasis verrucosa showing peculiar histologic features

A 60-year-old man had a 10-year history of linearly arranged verrucous papules on his left fingers in addition to psoriatic erythematosquamous papules and plaques on his trunk and extremities. The verrucous papules were clinically classified into two types: dome-shaped papules with a keratotic plug and crater-shaped papules with a central depression. Histopathologically, the former showed cup-shaped acanthosis with a parakeratotic column containing Munro's microabscesses, while the latter showed a cup-shaped epidermal invagination with Kogoj's spongiform pustule-like changes. Both types of papules were clinically diagnosed as psoriasis verrucosa, but their histologic features differed from those reported previously.