Delayed cutaneous manifestations of drug hypersensitivity.

Drugs may elicit a considerable variety of clinical signs, often affecting the skin and the mucous membranes. The most common are maculopapular exanthemas and urticaria, more rarely pustules, bullae vasculitic lesions, and lichenoid lesions may also be observed. Apart from the morphology, the chronology of the occurrence and the evolution of single skin lesions and exanthema are also paramount in the clinical diagnosis of cutaneous drug hypersensitivity. Often, the skin represents the only organ manifestation; however, it may be the herald for a systemic involvement of internal organs, such as in severe drug-induced hypersensitivity syndromes or anaphylaxis.