Actinic lichen planus in a Japanese man: first case in the East Asian population.

Actinic lichen planus (ALP) is a rare variant of lichen planus in which lichen planus develops on the light-exposed areas of the skin. ALP is reported to occur in the African, Middle Eastern,and Indian populations, with very few cases reported in Caucasians. Here, we report a case of ALP in a Japanese man; to the best of our knowledge, this is the first reported occurrence of ALP in the East Asian population. A 52-year-old Japanese man developed recurrent painful annular erythema on the face and hands. Histopathological examination of his skin biopsy revealed lichenoid-type infiltrates of lymphocytes and histiocytes. We established a diagnosis of ALP on the basis of the distribution of eruptions only on the sunlight-exposed areas and histological findings. Oral administration of systemic steroids proved effective in improving his condition. Lichen planus is known to be induced by an irritant (Koebner phenomenon);we believe that our patient is genetically susceptible to sunlight exposure and that sunlight acted as an irritant stimulating the development of ALP.