A 34-year-old Caucasian man presented to the ophthalmology emergency clinic with painless, bilateral upper and lower eyelid oedema since waking up that morning. The patient denied any history of lip swelling, tongue swelling, or shortness of breath. He reported a recent episode of an upper respiratory infection that had resolved. He was otherwise in good health. Medications included cetirizine HCl 10 mg a day and guaifenesin 1200 mg twice a day. He denied allergies to medications. Family history was negative for skin disease or angioedema.

Further history revealed that the patient had recurrent episodes of eyelid oedema from the age of 10 years, each lasting 5–7 days and with a frequency of two to five episodes per year. All episodes were associated with antecedent upper respiratory infection. The patient reported that each episode progressed similarly with spontaneous onset of bilateral, upper and lower eyelid swelling and conjunctival injection followed by irritation, foreign body sensation, difficulty focusing his vision and photophobia on day 3 or 4. All symptoms would then resolve without intervention by 1 week. Over the years he had observed that the eyelid skin between acute episodes had …