Fixed drug eruptions, bullous drug eruptions, and lichenoid drug eruptions.

Drug reactions are among the most common reasons for inpatient dermatology consultation. These reactions are important to identify because discontinuation of the offending agent may lead to disease remission. With the rising use of immunomodulatory and targeted therapeutics in cancer care and the increased incidence in associated reactions to these drugs, the need for accurate identification and treatment of such eruptions has led to the development of the "oncodermatology" subspecialty of dermatology. Immunobullous drug reactions are a dermatologic urgency, with patients often losing a significant proportion of their epithelial barrier; early diagnosis is critical in these cases to prevent complications and worsening disease. Lichenoid drug reactions have myriad causes and can take several months to occur, often leading to difficulties identifying the offending drug. Fixed drug eruptions can often mimic other systemic eruptions, such as immunobullous disease and Stevens-Johnson syndrome, and must be differentiated from them for effective therapy to be initiated. We review the clinical features, pathogenesis, and treatment of immunobullous, fixed, and lichenoid drug reactions with attention to key clinical features and differential diagnosis.