PERSISTENT ACTINIC EPIDERMOLYTIC HYPERKERATOSIS

Background: Epidermolytic hyperkeratosis is a distinctive histologic change noted in a variety of acquired and congenital dermatoses. Its pathogenesis is unknown. We have observed acquired epidermolytic hyperkeratosis in four Japanese men. Objective: Our purpose was to report four cases of acquired epidermolytic hyperkeratosis induced by sun exposure. Methods: Four cases were studied clinically, histopathologically, electron microscopically, and by tissue culture. Results: Flat, keratotic, slightly elevated, depigmented papules were located on the upper back, shoulders, and anterior aspect of the thighs. They appeared after excessive sun exposure. Depigmented macules coexisted with the pigmented macules. Histologic and ultrastructural examination revealed epidermolytic hyperkeratosis. Thick bundles of tonofilaments, which were also present in the cutaneous lesions, were seen in newly proliferated keratinocytes in cultures taken from depigmented papules. Conclusion: These results suggest that acquired epidermolytic hyperkeratosis may be induced by excessive sun exposure. We propose the term persistent actinic epidermolytic hyperkeratosis for these lesions.