Rapidly enlarging mycotic coronary artery aneurysm caused by bacterial seeding involving methicillin-sensitive Staphylococcus aureus and Klebsiella pneumoniae.

Coronary artery aneurysms are uncommon. A rare subcategory caused by infectious etiologies are called mycotic coronary artery aneurysms (MCAA), which have an exceedingly high mortality rate. In this report, we present a rare case of a rapidly expanding MCAA involving Staphylococcus aureus and Klebsiella pneumoniae affecting the left circumflex artery. Per our literature review, MCAA involving K. pneumoniae co-infection or superinfection have rarely, if ever, been documented. The aneurysm was discovered when the patient underwent coronary angiography for non-ST-elevation myocardial infarction. She was treated for bacteremia and upon reevaluation the aneurysm had grown approximately three times the original size. The patient had an aneurysmectomy with coronary artery bypass grafting due to the enlargement and size of the aneurysm. By highlighting this life-threatening disease, we hope to shed light on rare causes of MCAA and the importance of appropriate treatment. <Learning objective: Although rare, mycotic coronary artery aneurysms (MCAA) should be considered in the differential diagnosis of bacteremic patients presenting with symptoms of acute coronary syndrome. The MCAA diagnosis can be challenging due to nonspecific presentation and examination. Frequent surveillance and tempestive treatment results in favorable outcomes for the patient.>. Published by Elsevier Ltd on behalf of Japanese College of Cardiology.