Background <p>Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA), also known as Bland–White–Garland syndrome, is a rare congenital anomaly with an estimated incidence of approximately 1 in 300,000 live births. More than 90% of untreated patients die within the first year of life, and survival into late adulthood is exceptionally uncommon, with only a few cases reported beyond the sixth decade. Such late presentations are clinically important, because they demonstrate the role of extensive collateral circulation in survival and pose unique diagnostic and therapeutic challenges.</p> Case presentation <p>We report the case of a 70-year-old Iranian man who presented with acute chest pain lasting 12&#xa0;hours. On admission, his vital signs were stable, and electrocardiography revealed sinus rhythm with ST-segment depression in multiple leads. Serial troponin measurements were negative, and transthoracic echocardiography showed no abnormalities. Owing to persistent clinical suspicion, coronary computed tomography angiography was performed, which revealed anomalous origin of the left coronary artery from the pulmonary artery, with a markedly dilated right coronary artery supplying collaterals to the left coronary system. The patient underwent successful surgical reimplantation of the left main coronary artery into the aorta and was discharged in stable condition.</p> Conclusions <p>This case represents one of the oldest reported diagnoses of ALCAPA, underscoring the importance of maintaining a high index of suspicion for congenital anomalies even in elderly patients with atypical acute coronary presentations. It contributes to the limited literature on late survival without prior intervention and emphasizes the pivotal role of coronary computed tomography angiography (CCTA) in noninvasive diagnosis and surgical planning.</p>