[Erythema multiforme due to 5% imiquimod cream].

Imiquimod 5% cream (Aldara, 3M Pharmaceuticals) is a topical immunomodulator approved for the treatment of genital warts, actinic keratoses, and superficial basal cell carcinoma, although it is also used off-label in clinical practice for other dermatologic conditions. Although local side effects are most frequent, it can also produce systemic side effects. We describe the case of a patient who presented with exudative erythema multiforme that coincided with imiquimod treatment. The 66-year-old woman, with a history of hypertension, depression, and osteoarthritis, had been on treatment for many years with amiloride plus hydrochlorothiazide, lorazepam, citalopram, and dexibuprofen. She came to the outpatient clinic with facial lesions, evident actinic damage, several actinic keratoses on the dorsum of the nose and the upper lip, and a superficial basal cell carcinoma measuring 0.7 cm on the left cheek. Treatment with imiquimod cream was prescribed for all the lesions, to be applied to the actinic keratoses 3 times a week (alternate days) for 4 weeks, and to the superficial basal cell carcinoma 5 times a week for 6 weeks. At the end of the second week of treatment, the patient had developed an intense local reaction at the sites of application, presenting as crusting, edema, and erythema; treatment with imiquimod was interrupted. It was recommenced 7 days later, but within 14 days lesions appeared on the chest, forearms, hands, and legs, accompanied by a burning sensation, a worsening of the facial lesions, a feeling of fever, and general malaise. Physical examination revealed the whole of the nose, the upper lip, and the left cheek to be covered by extensive areas of crusting that left erosions when lifted, and several round erythematous papules, measuring between 0.5 cm and 0.8 cm, in the central upper chest area, on the extensor surfaces of the forearms and lower legs, and on the dorsum of the hands; some of these papules had central erosions and others presented a target morphology (Figures 1 and 2). There was no involvement of the palms, soles, or mucosas. The patient denied having taken any drugs other than her usual medication, or having previously had herpes simplex or any other infection. Biopsy of a papule revealed epidermal necrosis, involvement of the dermal-epidermal interphase with damage to the basal layer, and perivascular lymphocytic inflammation in the papillary dermis, all consistent with exudative erythema multiforme (Figure 3). Treatment with imiquimod was suspended, and the lesions were treated with topical antibiotics; her usual medication was maintained. The patient responded well, with complete resolution of the systemic and cutaneous alterations within a few days. Imiquimod is a topical immunomodulator whose antitumoral and antiviral activity results from its capacity to stimulate both innate and acquired immune responses. Although its precise Figure 1 Erythematous papules on the extensor surfaces of both forearms, some with central erosions.