Fixed Drug Eruption

• A fixed drug eruption (FDE) is an adverse cutaneous reaction to an ingested drug, characterized by the formation of a solitary (but at times multiple) erythematous patch or plaque. The most commonly implicated agents are listed in Table 23-6.
• If the patient is rechallenged with the offending drug, the FDE occurs repeatedly at the identical skin site (i.e., fixed) within hours of ingestion.
• Skin symptoms: Usually asymptomatic. May be pruritic, painful, or burning.
• Skin Lesions. A sharply demarcated macule, round or oval in shape. Initially erythema, then dusky red to violaceous (Fig. 23-6A). Most commonly, lesions are solitary and can spread to become quite large, but they may be multiple with random distribution. Lesions may evolve to become a bulla (Fig. 23-6B) and then an erosion. Eroded lesions, especially on genitals or oral mucosa, are quite painful. After healing, dark brown with violet hue postinflammatory hyperpigmentation. Genital skin (see Section 34) is frequently involved site (Fig. 23-7), but any site may be involved; perioral or periorbital (Fig. 23-6A). They occur in conjunctivae or oropharynx.
• Dermatopathology. Similar to findings in erythema multiforme and/or TEN but with pigment incontinence.
• Patch Test. An inflammatory response occurs in only 30% of cases.
• FDE resolves within a few weeks of withdrawing the drug. Recurs within hours after ingestion of a single dose of the drug.
• Management. Withhold offending drug. Noneroded lesions: Potent topical glucocorticoid ointment. Eroded lesions: Antimicrobial ointment. For widespread, generalized, and highly painful mucosal lesions, oral prednisone 1 mg/kg body weight tapered over a course of 2 weeks.