Arterial thoracic outlet syndrome due to a first-rib anomaly causing brachial artery embolic occlusion: a case report.

Arterial thoracic outlet syndrome is a rare condition caused by compression of the subclavian artery at the thoracic outlet, which often leads to delayed diagnosis and potentially severe outcomes such as upper limb necrosis. We report a case of a man in his 20s who presented with coldness in the right fingers, exacerbated by cold environments. Chest radiography revealed abnormal bone structures, and contrast-enhanced computed tomography confirmed stenosis and post-stenotic dilation of the right subclavian artery, thrombus formation, and occlusion of the brachial artery. Although bilateral first-rib anomalies were present, three-dimensional volume-rendered imaging identified focal arterial compression on the right side due to abnormal fusion of the first and second ribs, leading to a definitive diagnosis of arterial thoracic outlet syndrome. This case highlights that reliance on routine two-dimensional imaging alone may contribute to diagnostic delay, whereas selective use of three-dimensional reconstruction can provide critical anatomical insight, enabling accurate diagnosis and appropriate management in patients with complex thoracic outlet anatomy.