Giant left main coronary artery aneurysm in a young adult female with suspected incomplete Kawasaki disease: a case report.

Background: Kawasaki disease (KD) is a systemic vasculitis predominantly occurring in pediatric populations. Giant coronary artery aneurysm (gCAA) involving the left main coronary artery (LMCA) is an extremely rare long-term complication of KD. Adult-onset or late-diagnosed KD-related giant LMCA aneurysm in young female patients represents a rare clinical entity with high risks of intracoronary thrombosis, myocardial infarction, and sudden cardiac death. Due to absent classic childhood KD symptoms, such aneurysms are commonly misdiagnosed as atherosclerotic lesions or congenital coronary malformations upon first admission. Notably, no gold-standard laboratory test exists to confirm remote childhood KD; diagnoses in adult survivors rely heavily on exhaustive exclusion of alternative vasculopathies combined with pathognomonic coronary angiographic morphology, rather than angiographic findings alone. Case presentation: This study reports a case of a 35-year-old previously healthy female with a one-month history of intermittent exertional chest pain. She denied classic childhood manifestations of KD and had no conventional cardiovascular risk factors. Invasive coronary angiography confirmed a giant fusiform LMCA aneurysm with a mean diameter of 12.78 mm, accompanied by mild mural calcification and reduced intracavitary perfusion. Typical beaded saccular and fusiform aneurysms were also observed in the left anterior descending and right coronary arteries (RCA). Laboratory tests excluded autoimmune vasculitis,infectious arteriopathy and atherosclerotic heart disease. Combined with highly characteristic angiographic coronary vasculopathy patterns and complete exclusion of competing diagnoses, we established a presumptive diagnosis of chronic vascular sequelae derived from unrecognized incomplete KD, rather than a definitive confirmed diagnosis. The patient received lifelong dual antiplatelet plus anticoagulant therapy, and underwent drug-coated balloon angioplasty for RCA lesions. No early major adverse cardiovascular events were documented within the 6-month structured short-term follow-up; long-term thrombotic risk remains persistent and requires prolonged serial surveillance. Conclusion: Unrecognized incomplete KD in childhood may progress to symptomatic giant LMCA aneurysms in young adulthood, even without typical acute KD manifestations. For young female patients with idiopathic isolated giant LMCA aneurysms, antecedent occult incomplete KD should be highly suspected. Long-term individualized antithrombotic therapy and close imaging surveillance are essential to prevent life-threatening cardiovascular complications.