Ecase D-13

Paul Lindenfeld, M.D.

June 2-6, 2003

Case Vignette

A 32 year old female with a history of asthma is worked into your afternoon schedule at the last minute. She was jogging with a friend about 1 hour ago. They stopped to share a Power Bar and shortly thereafter her mouth began to itch and her throat felt as it were closing up. She began to wheeze, became nauseated, and vomited her Power Bar. She used her Albuterol MDI which helped reduce the wheezing somewhat. Her friend carries an Epi Pen because of a bee sting allergy. The friend gave her an IM injection with the Epi Pen because she thought she was having an allergic reaction. The patient’s itching, wheezing and nausea subsided and she feels OK now. She thinks she may have had a reaction to the peanut butter in her Power Bar and she wants to get checked out.

• Meds: OCP’s, Albuterol prn

• ALL: NKDA, Asthma. No hx of food allergy.

• PMH: Asthma

• Vitals: BP 110/76, P 95, T 98.7, RR 14. No orthostasis.

• Anxious appearance

• Chest exam remarkable for wheezing with forced expiration only

Question:

You should next:

1. Empirically dx peanut allergy. Prescribe Epi Pen and recommend she carry Benadryl tablets with her.
2. Send her for skin testing with nut allergens and radioallergosorbent (RAST) testing, prescribe Epi Pen and liquid Benadryl pending test results.
3. Arrange for her to go to the E.R. ASAP and schedule a follow-up appointment within 1 week.
4. Arrange for testing as outlined in “b”, prescribe Epi Pen, but tell patient that you think this was a severe asthma exacerbation triggered by exercise and you will discuss further asthma treatment options once food allergy has been ruled out.

(Answer question before reading further)

Correct answer:
c) Biphasic reactions occur in 1/3 of patients with severe anaphylactic reactions to peanuts. 90% of these reactions will occur within 4 hours of the initial reaction. If a biphasic reaction does occur, it is more likely to be refractory to treatment and require mechanical ventilation. For these reasons it is standard of care to observe this patient for at least 4 hours in an environment equipped to treat anaphylactic reactions.

Incorrect answer explanations:

1. a) You should proceed with further diagnostic testing as outlined in b. This patient should carry an Epi Pen. She should also carry liquid Benadryl as it is absorbed faster than the tablet form.

2. b) Proving that the patient has IgE specific antibodies to peanuts is necessary for diagnosis. This could be done with skin testing or a RAST with IgE levels > 15kU/L (patients with the latter have >95% likelihood of an allergic reaction if they ingest peanuts). Patients with negative skin testing and RAST IgE peanut antibodies < 15 should be referred to an allergist for oral peanut challenge testing in a controlled environment to confirm the diagnosis.

4. d) Patients with peanut allergy often have a history of asthma and other allergies. This patient’s symptoms of oral pruritus, airway constriction and N/V (due to bowel wall edema) point to an anaphylactic reaction and away from asthma.

The patient is observed in the E.D. for three hours and discharged home uneventfully. She is given an Epi Pen and oral Benadryl by the E.D. physician to be used prn. She also completes a 3-day course of Prednisone and an H1 blocker without event. RAST testing shows a peanut specific IgE level of 58 kU/L. Skin prick testing is reactive to peanuts and (God forbid) pistachios. She presents for follow up.

You counsel her that:

• She has a >95% likelihood of an allergic reaction to peanut ingestion with high RAST levels.
• 1/3 of those with peanut allergies also have allergies to tree nuts (walnuts, cashews, pistachios).
• She needs to check food labels for presence of peanuts and pistachios. She should be wary of places where food may have come into contact with nuts (for example, the ice cream sundae buffet down at the Ponderosa).
• She needs to have a written emergency plan such as the one available at the Food Allergy and Anaphylaxis Network website: www.foodallergy.org
• She needs to carry her Epi Pen and liquid Benadryl with her because the average person with a peanut allergy develops a reaction every 3 to 5 years despite precautions.
• She should go to the nearest E.D. after a reaction has occurred, especially if she used her Epi Pen.

More peanut allergy information

• 1% of the U.S. population are allergic to peanuts and/or tree nuts.
• Nut allergies account for most cases of fatal or severe anaphylactic reactions in the U.S.
• 80% of people who die from food allergy were not given information on how to avoid accidental food ingestion or epinephrine by their doctor.
• Most peanut allergies (in contrast to my case) begin in childhood and persist into adulthood.
• Some doctors recommend that children with a family history of atopy should avoid peanuts until age 3 and that their mothers should not ingest peanut products if they are breast-feeding to try to prevent development of peanut allergy.
• A new drug that will supposedly reduce the severity of allergic reactions for those with peanut allergy is currently in clinical trials.

Editor’s note: Ipratropium bromide (Atrovent) and Combivent MDIs contain soy lecithin as a suspending agent. Because soy is related to peanuts, people with peanut allergies should not be given either of these inhalers. Atrovent nasal spray does not contain soy lecithin, and so is okay.

Reference

NEJM, Peanut Allergy, 4/25/02, Vol. 346, No. 17, pgs. 1294-1299

NEJM, Peanut Allergy, 4/25/02, Vol. 346, No. 17, pgs. 1320-1322