Pantoprazole-induced anaphylactic asthma and Type I Kounis syndrome: a case report and literature review.

Background: Proton pump inhibitors (PPIs) are among the most frequently prescribed medications and are generally considered to have a favourable safety profile. Nevertheless, immediate hypersensitivity reactions may occur and, in exceptional circumstances, can precipitate Kounis syndrome (KS), an acute coronary syndrome resulting from the activation of inflammatory pathways. We describe an elderly patient who developed severe anaphylaxis with Type I KS shortly after intravenous pantoprazole administration in the presence of an unsuspected myocardial bridge, and discuss the potential clinical implications. Case summary: An 85-year-old woman with a 30-year history of well-controlled bronchial asthma was admitted with community-acquired pneumonia. During hospitalization, she received intravenous pantoprazole (40 mg) for acid reflux. Within five minutes of the infusion, she developed a widespread erythematous rash, severe bronchospasm, profound hypotension (74/56 mmHg), and ST-segment elevation of approximately 0.3 mV in leads I, aVL, and V₁ to V₄. Emergency coronary angiography demonstrated no obstructive coronary artery disease but identified a myocardial bridge involving the mid-left anterior descending artery, producing nearly 90% systolic compression. Serial cardiac troponin and NT-proBNP concentrations remained within the normal range. Assessment using the Naranjo Adverse Drug Reaction Probability Scale yielded a score of six, indicating a probable causal relationship between pantoprazole and the adverse event. The patient was treated with methylprednisolone (80 mg). The recovery occurred within 2 h. Conclusion: This case highlights that intravenous pantoprazole may rarely trigger life-threatening Type I Kounis syndrome. It also raises the possibility that a pre-existing myocardial bridge can accentuate coronary vasospasm during severe allergic reactions, thereby contributing to the clinical presentation. Based on this experience and the available literature, we propose a practical management algorithm to facilitate timely diagnosis and treatment in similar clinical settings.