It is possible that in drug-induced lichen planus/lichenoid reaction, CD8+ T cells may be activated by a drug molecule expressed by basal keratinocytes in association with MHC class I molecules and that the activated cytotoxic CD8+ T cells may trigger necrosis or apoptosis of keratinocytes via the Fas-Fas L, granulysin, or perforin/granzyme pathways [23, 42, 43]. This evidence concerns the gene CD8A and lichen planus.