Erythema multiforme presenting as chronic oral ulceration due to unrecognised herpes simplex virus infection

Abstract

Conflict of interest: there are no conflicts of interest. A 54‐year‐old white woman was referred with a 3‐month history of persistent, painful mouth ulcers occurring on the lip and tongue (Fig. 1), rendering talking and eating painful. There had been no improvement with topical steroid preparations, and the only treatment that cleared the ulcers was a 5‐day course of oral prednisolone 30 mg/day. However, repeated courses were required as the ulcers recurred within a few days of each course. A biopsy of the oral ulcers revealed features consistent with either an allergic response or erythema multiforme (EM). Negative immunofluorescence excluded immunobullous disease. Patch testing did not reveal any relevant allergens. Four months following the initial presentation to our department, the patient developed classic target lesions over her chest and arms. Histologically, an epidermal pattern of EM was confirmed. At this stage, azathioprine was added as a steroid‐sparing agent in view of her cushingoid appearance. However, it was not until a routine appointment 9 months after her initial presentation to our department that the aetiology of our patient's EM became clear. At this visit, examination revealed grouped vesicles over her buttock typical of herpes simplex virus (HSV) infection. These lesions had been a recurring problem, noted following a sexual assault 9 years previously, and had been confirmed on culture. Because of this traumatic association, the information had not previously come to light.