Fixed drug eruption: a disease mediated by self-inflicted responses of intraepidermal T cells.

It is difficult to dissect disease-causing T cells and anti-inflammatory T cells in a biopsy specimen obtained at a given time, which would represent a single time point in the development of the lesions. In fixed drug eruption (FDE), the resting lesions long after clinical resolution have many clues to identify the disease-causing T cells, because they contain a large homogeneous population of CD8(+) T cells that are distributed along the epidermal basal layer and have the capacity to rapidly produce large amounts of IFN-gamma. These intraepidermal CD8(+) T cells are likely to be a major actor in epidermal injury observed in FDE lesions. In this review, we ask how they arise and how they cause epidermal injuries, which present with a wide spectrum of clinical manifestations and are often mistaken as signs of other skin disease.