A case of linear lichen planus pigmentosus.

Lichen planus pigmentosus (LPP) is chronic pigmentary disorder that shows diffuse or reticulated hyperpigmented, dark brown macules on the sun-exposed areas such as the face, neck and other flexural folds. Clinically, it is different from classical lichen planus because LPP has a longer clinical course and it manifests with dark brown macules. In case of LPP, involvement of the scalp, nail or mucosal area is rare. The histopathological findings of the lesions show an atrophic epidermis, the presence of melanophages and a vacuolar alteration of the basal cell layer with a sparse lymphohistiocytic lichenoid infiltration. Although there have been a few reports of LPP, there have only 3 cases of linear LPP along the lines of Blaschko in the Korean dermatologic literature. Our patient had lesions on the neck and chin with a linear pattern. In this report, we describe a very rare case of LPP with a linear distribution related to Blaschko's lines on the neck and chin areas.