Omalizumab as an Effective Therapy for Testosterone-induced Angioedema in a Transgender Person: A Case Report

Background: Gender affirming hormone therapy is a cornerstone for transgender and gender diverse individuals. We report the first case in the literature of systemic allergic reactions to testosterone therapy and how we succeeded in managing them. Case Presentation: A 19-year-old transgender person assigned female at birth started testosterone therapy to achieve full masculinization. For 14 months, testosterone was administered via transdermal and intramuscular preparations and was well tolerated. However, the individual later developed several angioedematous reactions at different times, despite the use of various testosterone formulations. Allergy evaluations, such as blood tests, SPT, IDT, and drug challenges for both testosterone and excipients, were conducted; the drug challenge for testosterone was positive, confirming it as the trigger of angioedema. The use of omalizumab 150 mg subcutaneously every two weeks allowed the patient to resume testosterone therapy without further systemic reactions. This helped to reduce the patient’s perceived stress and supported his psycho-physical well-being. Conclusion: Omalizumab was able to successfully manage the systemic allergic reactions to testosterone therapy, and this report could be useful for other clinicians facing similar clinical situations.