During her inpatient stay, this woman developed a painful, unilateral erythematous rash in a butterfly distribution. It predominantly affected the right malar region. Initial differential diagnoses included herpes zoster and systemic lupus erythematosis, but it became clear that this was photosensitivity induced by oral doxycycline. Her bed was situated so that the sun shone on to one side of her face for most of the day. After the antibiotic was stopped and the curtains were drawn, the rash resolved rapidly.

Mike Beadsworth, specialist registrar, Saif Al-Abri, specialist registrar, Fred Nye, consultant, N Beeching, senior lecturer, tropical and infectious disease unit, Royal Liverpool University Hospital, Liverpool L7 8XP