Allergic drug eruption secondary to intravenous acyclovir.

A 62-year-old woman presented at our department 10 days after returning from a trip to Alaska. Over the previous 7 days she had developed headache, elevated temperature and disseminated erythematous vesicles. The only medication she was taking at this time was L-thyroxine 75 mg once daily for treatment of hypothyroidism. Her skin showed widespread vesicles on an erythematous base without palmar and plantar affection. There was no mucous membrane involvement. The patient was otherwise healthy. A diagnosis of disseminated herpes zoster infection was made subsequently, indicating the need for systemic antiviral treatment. A polymerase chain reaction (PCR) was performed and confirmed varicella zoster infection. According to the patient, she had formerly developed eczema to external acyclovir and external betamethasone. Otherwise, her personal and family history was negative for skin diseases. Due to this medical history of a potential acyclovir sensitization a prick-test was performed, whose results were negative. Given the negative prick results, a test dose of 70 mg acyclovir (1 mg/kg bodyweight), equivalent to 10% of the regular dose, was given intravenously. After 8 h, the patient developed a plain macular erythema with slight infiltration of the popliteal fossae and the trunk (Fig. 1). There was no other medication given at that point. The rash was topically treated with corticosteroids (betamethasone), leading to a complete remission of the exanthema within 2 days. The zoster infection also regressed with out any further treatment or any complications. There was no evidence for neurological involvement at any point. For further diagnostic work-up, we presented the patient to our allergy department, where prick-testing and epicutaneous testing for acyclovir (tablets), valacyclovir (tablets) and a topical preparation (acyclovir, propylene glycol, natrium lauryl) were performed. Patch tests showed a pronounced eczematous reaction (++) at 48, 72 and 96 h for each of the 3 substances. Prick-testing remained negative, as did epicutaneous and prick-testing of corticosteroid series (Fig. 2).