Kounis syndrome type III triggered by stents in patients with coronary artery disease: A review of clinical cases

Kounis syndrome (KS) type III is a rare but life-threatening condition in which an acute allergic, anaphylactic, or anaphylactoid reaction precipitates acute coronary syndrome due to thrombosis or restenosis of a previously implanted coronary stent. The pathophysiological mechanism involves IgE-mediated or non-IgE-mediated mast cell activation, leading to coronary vasospasm, destabilization of atherosclerotic plaques, and intrastent thrombosis. Known triggers include various allergens such as medications (notably antibiotics and nonsteroidal anti-inflammatory drugs), metallic or polymeric stent components, and drugs eluted from the stent surface. A review of relevant clinical cases from PubMed and Scopus (1991-2025; 6 publications meeting the inclusion criteria, reporting 6 cases) showed a mean patient age of 66 ± 11 years, with a male predominance (4/6). Only 3 patients had a history of allergic disease. Clinical manifestations included chest pain (100%), cutaneous rash (2 cases), and ST-segment elevation on electrocardiogram (4 cases). Management included reperfusion therapy, corticosteroids, antihistamines, and dual antiplatelet therapy. Outcomes were generally favorable, although 1 patient died 3 years later due to KS-related complications. KS type III requires urgent recognition and simultaneous treatment of both the allergic reaction and coronary obstruction. In cases of unexplained stent thrombosis or restenosis, KS should be considered in the differential diagnosis.