Mikey Gets Cut by Occam's Razor

A 62-year old woman with a past medical history significant for hypertenstion and rheumatoid arthritis came to the office for a follow-up visit two days after she had been diagnosed with acute angioedema in a local Emergency Department. She had been at Mohegan Sun on Saturday morning with her husband. She had a pastry for breakfast around 9AM. At 11AM her arthritis flared up, but she realized that she left her meds at home. She bummed some acetaminophen (generic) from her husband, who happened to carry some along with at least one other medication in the same pill box. 30 minutes later, the patient experienced the onset of severe sore throat and felt that her tongue was beginning to swell. She and her husband immediately drove to the ED. The ED noted that the patient takes Zestril (lisinopril) for her hypertension. They gave her Benadryl, prednisone, and instructed her to avoid taking the Zestril until she spoke with her family physician.

At the visit, the patient notes that her throat is still sore, and that her tongue is still mildly swollen. Physical exam is notable for mild glossitis and swelling of the right submandibular gland. There is no pharygneal erythema or swelling.

Breakdown of her medical history reveals that she has developed allergies to sulfa drugs and several anti-hypertensive medications, including generic lisinopril, which elicits cough from the patient. She is allergic to walnuts, and one of her brothers is allergic to Brazil nuts.

I do a Medline search looking at side effects of lisinopril, and it returns several articles associating angioedema with long-term use of ACE inhibitors. Proud of my evidence-based knowledge, I present my case to my preceptor, who listens with indifference or boredom, I can't tell which.

What caused the acute angioedema? Was it:
a) Zestril
b) the generic acetaminophen
c) some other medication out of her husband's pillbox
d) The Mystery Pastry

My preceptor decided that the most likely culprit was the Mystery Pastry. The patient has been taking Zestril for 5 years without incident. An anaphylactic reaction to the inert components of the acetaminophen pill is highly unlikely. We refer her to an allergist to screen for food allergies, and restart her Zestril because her blood pressure is elevated. There were no medications in her husband's pillbox that were associated with any of her allergies.

And just in case, we also write a prescription for an Epipen.

Moral of the story: The sexiest explanation (Zestril-induced angioedema) isn't necessarily the correct one. Occam's Razor - the simplest explanation is the most likely.

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Right now I'm listening to: This Beautiful Life, Big Bad Voodoo Daddy