Isolated Lip Angioedema Associated With Spironolactone: A Case Report.

Spironolactone is a widely used mineralocorticoid receptor antagonist with a well-established adverse-effect profile; however, angioedema is uncommon and a poorly recognized adverse reaction. We report a case of suspected isolated lip angioedema associated with spironolactone therapy in a 74-year-old woman. The patient presented with a two-week history of persistent upper-lip swelling and facial heaviness without urticaria, pruritus, tongue or oropharyngeal involvement, or symptoms of airway compromise. Although spironolactone had been prescribed approximately one year earlier, the patient had been poorly adherent and had resumed consistent daily use approximately one month before the onset of symptoms. She continued spironolactone despite the development of swelling. Clinical evaluation and laboratory investigations did not identify an alternative cause, and serum complement C4 was within the normal range. C1-esterase inhibitor antigenic and functional assays were unavailable. Spironolactone was discontinued, resulting in substantial improvement by Day 7 and complete resolution by Day 14 without recurrence. The Naranjo Adverse Drug Reaction Probability Scale yielded a score of 6, consistent with a probable adverse drug reaction. This case highlights isolated lip angioedema as a potential, although rare, adverse reaction to spironolactone and underscores the importance of establishing actual medication exposure when assessing suspected drug-related reactions. Recognition of uncommon medication triggers may facilitate timely withdrawal of the offending agent and prevent potentially more severe recurrence.