Fixed Drug Eruptions

Adverse reactions to medications are common and often manifest as a cutaneous eruption.

Drug-induced cutaneous disorders frequently display a characteristic clinical morphology such as morbilliform exanthem, urticaria, hypersensitivity syndrome, pseudolymphoma, photosensitivity, pigmentary changes, acute generalized exanthematous pustulosis, lichenoid dermatitis, vasculitis, Stevens-Johnson syndrome, or fixed drug eruption (FDE). 

The term fixed drug eruption describes the development of one or more annular or oval erythematous patches as a result of systemic exposure to a drug; these reactions normally resolve with hyperpigmentation and may recur at the same site with reexposure to the drug. Repeated exposure to the offending drug may cause new lesions to develop in addition to "lighting up" the older hyperpigmented lesions.

Several variants of fixed drug eruption have been described, based on their clinical features and the distribution of the lesions. These include the following:

• Pigmenting fixed drug eruption
• Generalized or multiple fixed drug eruption
• Linear fixed drug eruption
• Wandering fixed drug eruption
• Nonpigmenting fixed drug eruption
• Bullous fixed drug eruption
• Eczematous fixed drug eruption
• Urticarial fixed drug eruption
• Erythema dyschromicum perstans–like fixed drug eruption
• Vulvitis
• Oral
• Psoriasiform
• Cellulitislike eruption

Source http://emedicine.medscape.com/article/1336702-overview