Drug eruption secondary to aciclovir with recall phenomenon in a dermatome previously affected by herpes zoster

Classically, recall dermatitis refers to chemotherapy-induced reactivation of skin damage caused by radiotherapy months, or even years, earlier. The concept of recall dermatitis has now been extended to include radiation recall dermatitis induced by other drugs, ultraviolet radiation, extravasation of drugs, and allergic contact dermatitis. We now describe recall dermatitis along the residual cutaneous lesions of a previous thoracic herpes zoster in a patient who developed a drug eruption after oral administration of aciclovir. The most striking feature consisted of confluent linear erythema along the dermatomes previously involved by the herpes zoster episode. Histopathologic study demonstrated small foci of spongiosis, vacuolar changes involving the basal layer of the epidermis and single necrotic keratinocytes scattered within the epidermis. The papillary dermis appeared oedematous and with dilated blood capillaries surrounded by a sparse inflammatory infiltrate composed mainly of lymphocytes. Serial sections failed to demonstrate cytologic changes of herpes varicella zoster infection. We interpreted this case as an example of recall dermatitis because the widespread cutaneous eruption secondary to aciclovir was more intense in skin previously compromised by herpes varicella zoster infection. To the best of our knowledge, recall dermatitis has not been described before at the site of previous involvement by herpes zoster.