Case Report: Recurrent Kounis syndrome complicated with acute coronary stent thrombosis

Background Kounis syndrome manifests as an acute coronary syndrome induced by an allergic or hypersensitivity reaction. Kounis syndrome consists of three types: Type I is characterized by coronary artery spasm in normal or near-normal arteries, Type II by the rupture of coronary artery plaques, and Type III by the formation of thrombus within the coronary artery stent. Recurrent episodes of Kounis syndrome are uncommon in clinical practice. We herein report a case of recurrent Kounis syndrome, in which the second episode presented as Type III Kounis syndrome. Case presentation We report a patient who experienced two acute coronary events triggered by Kounis syndrome within approximately one month—an uncommon presentation. One episode manifested as chest pain accompanied by tongue swelling, and was diagnosed as Type II Kounis syndrome and treated with cetirizine for anti-allergic purposes. The second episode occurred about one month later with persistent chest pain and recurrent tongue swelling, and coronary angiography confirmed acute coronary stent thrombosis. Taken together with the allergic manifestation (tongue swelling) accompanying both events, the second episode fulfilled the criteria for Type III Kounis syndrome. Subsequently, we performed emergency procedures to open the blocked coronary artery and administered glucocorticoid therapy. The patient's symptoms improved. Conclusion Despite antihistamine therapy with cetirizine in the first episode, this patient still developed subsequent stent-related thrombosis. This case highlights that combined anti-allergic therapy including glucocorticoids may be considered at an early stage for Kounis syndrome patients with unidentified allergens, to mitigate potential allergic-mediated cardiac risk. Nevertheless, we cannot conclude glucocorticoids definitely prevent stent thrombosis, as avoidance of unrecognized allergens may also contribute to clinical improvement.