Adverse reactions to medications are common and important cause of iatrogenic illness. Severe cutaneous adverse drug reactions include toxic epidermal necrolysis, Stevens–Johnson syndrome, drug reaction with eosinophilia and systemic symptoms, and acute generalized exanthematous pustulosis, which together constitute 2% of all adverse drug reactions and may be life-threatening. Less severe drug-induced skin reactions such as exanthems, urticaria, lichenoid drug rashes, and fixed drug eruptions are more common, sometimes termed benign cutaneous adverse reactions, and generally resolve without sequelae. Drugs may also cause adverse events due to alteration of the normal function of the skin or its appendages. This may take the form of photosensitivity, abnormal pigmentation, or disrupted growth of hair or nails.
HLA Association with Drug-Induced Adverse Reactions