Severe recurrent anaphylaxis: investigating underlying mechanisms beyond IgE-mediated allergy - a case report.

Anaphylaxis is a sudden, life-threatening, and generalized allergic reaction that develops within minutes to hours following exposure to an allergen. Cutaneous, respiratory, and cardiovascular symptoms may occur in various combinations, and the severity of the reaction can vary, potentially leading to anaphylactic reactions, which, if untreated with epinephrine, may be fatal. Although anaphylaxis is most commonly caused by allergic mechanisms, cofactors and comorbidities can contribute to increased severity. We present the case of a 34-year-old man who repeatedly experienced severe anaphylactic reactions after consuming products containing defensins. Comprehensive diagnostic evaluation confirmed an IgE-dependent allergic reaction to inhalant defensins. Additionally, histamine intolerance was suspected, and suspicion of systemic mastocytosis (SM) was raised. This study aims to describe the diagnostic process and highlight the challenges in differentiating clinical symptoms arising from overlapping pathophysiological mechanisms in these conditions.