Lichenoid drug eruption, also called drug-induced lichen planus, is an uncommon cutaneous adverse effect of several drugs [1-4]. It is characterized by a symmetric eruption of flat-topped, erythematous or violaceous papules resembling lichen planus on the trunk and extremities. The time interval between the initiation of the offending drug and the appearance of the cutaneous lesions varies from months to a year or more and depends upon the class of drug, dose, host reaction, and concurrent medications . Histologic examination reveals lichenoid interface dermatitis .
This topic will discuss the pathogenesis, clinical manifestations, diagnosis, and treatment of lichenoid drug eruptions. Lichen planus and other types of cutaneous adverse reactions to drugs are discussed separately.
The incidence of lichenoid drug eruption is not known. It occurs more frequently in older adults without sex predilection. In small case series, the average age at onset was 44 to 66 years [6-8].
ETIOLOGY AND PATHOGENESIS
Immunologic mechanism — The pathogenetic mechanism of lichenoid drug reaction is incompletely understood. T cells, keratinocytes, dendritic cells, and endothelial cells, which express activation markers, costimulatory molecules, and adhesion molecules (eg, MHC-class-II molecules, lymphocyte function-associated antigen [LFA] 1, L-selectin, intercellular adhesion molecule [ICAM] 1) are thought to be involved in the inflammatory reaction that ultimately leads to the apoptosis of basal keratinocytes .