C32-07 Severe Allergic Reactions With Odactra: A Dermatophagoides Farinae and Dermatophagoides Pteronyssinus Allergenic Extract

Introduction Odactra (Dermatophagoides farinae and Dermatophagoides pteronyssinus allergenic extract) is the first allergen extract approved by the United States Food and Drug Administration to be administered sublingually. Systemic allergic reactions, including anaphylaxis and angioedema, have been reported with house dust mite extracts, although such events are rare. The mechanism involves IgE-mediated hypersensitivity to mite allergens, which are present in Odactra and have been shown to trigger both local and systemic immune responses. To ensure patient safety, the initial dose is typically given in a healthcare setting, where the patient is monitored for 30 minutes. We report an unusual case of anaphylaxis and angioedema triggered by Odactra, highlighting a rare but serious potential complication of this therapy. Case Presentation A 40-year-old woman with a history of multiple allergies and fibromyalgia experienced an anaphylactic reaction with angioedema after receiving her first dose of sublingual dust mite extract at an allergist’s office. She developed throat and tongue swelling, shortness of breath, and hives within minutes. She was treated with epinephrine and diphenhydramine, then transported to the ED, where she was found to have angioedema. She was started on an epinephrine infusion, steroids, and antihistamines, and was admitted to the intensive care unit. ENT evaluation showed no airway compromise. Her symptoms improved and the epinephrine drip was titrated off within two hours of initiation. She remained stable without the need for vasopressors overnight and was subsequently discharged home the next day on a five-day steroid taper, and an outpatient follow-up with her primary Allergy and Immunology clinic. Discussion The frequency of anaphylaxis or angioedema associated with Odactra is very low, estimated at less than 0.1% for anaphylaxis; angioedema is similarly rare. The American Academy of Allergy, Asthma, and Immunology notes that systemic reactions to dust mite immunotherapy are rare, and severe reactions (Grade III or higher) are exceedingly uncommon with sublingual therapy. We therefore report a rare case of Odactra-induced anaphylaxis, which in our case did not necessitate intubation but did require an epinephrine drip and intensive monitoring.