Severe Drug Hypersensitivity Reactions: Clinical Pattern, Diagnosis, Etiology and Therapeutic Options

Severe cutaneous adverse reactions (SCAR) are known for a high morbidity and mortality. They may be life-threatening for the affected patient and difficult to accomplish for the patient's family and the treating physician. Such conditions include not only bullous reactions like toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS), but also acute generalized exanthematous pustulosis (AGEP) and drug reaction with eosinophilia and systemic symptoms (DRESS). Since clinical pattern, etiology, prognosis and treatment differ among these severe skin reactions, a clear diagnosis based on a comprehensive clinical examination, skin biopsy, and specific laboratory tests is necessary. Because most of these reactions are caused by drug intake, a thorough history of medication use has to be obtained. However, there are cases with an infectious or idiopathic cause. In any case it is crucial to identify the most likely cause and rapidly discontinue the inducing agent, if a drug cause is suspected. This is associated with the patient`s prognosis which is often poor for bullous reaction. In addition, patient's age, underlying conditions, and the extent of skin detachment play a major role in terms of prognosis. Severe cutaneous adverse reactions are T-cell-mediated reactions, and certain alleles of human leukocyte antigens (HLA) are involved in the activation of T-cells with cytotoxic effect. The therapeutic options depend on the clinical diagnosis. For all reactions a symptomatic and adequate supportive therapy is necessary, in some cases a systemic immunomodulating therapy can be useful.