Acquired angio-oedema as a mimicker of drug allergy.

A woman in her 50s with a history of splenic marginal zone lymphoma developed severe angio-oedema after a scaling and root planing dental procedure. She was seen by multiple physicians who treated her for presumed local anaesthetic allergy and subsequently referred her to an academic allergy centre for specialised drug allergy testing. On evaluation, her clinical history was suggestive of acquired angio-oedema, which was confirmed by bloodwork. This case report underscores key clinical pearls that should prompt clinicians to consider a diagnosis of acquired angio-oedema, a rare bradykinin-mediated disease which can present with acute life-threatening angio-oedema and for which a clinical diagnosis is critical to selecting the appropriate acute therapy. The case also highlights the utility of a complement C4 test when patients present acutely with angio-oedema of unknown aetiology, especially in the emergency department.