Rupture of an Intercostal Artery Pseudoaneurysm in a 14-Year-Old Boy: A Case Report

Objective:Challenging differential diagnosis Background:Intercostal artery pseudoaneurysm is a rare yet clinically important vascular cause of hemothorax that can be overlooked when initial manifestations mimic infectious pulmonary disease. Case Report:A 14-year-old boy presented with a 1-week history of fever, cough, and progressive right-sided chest and back pain.Initial computed tomography (CT) showed inflammatory opacities in the right lower lobe accompanied by pleural thickening, yielding a presumptive diagnosis of pneumonia.Antibiotic therapy alleviated fever and cough; however, the pain intensified and the right pleural effusion expanded.Ultrasound-guided thoracic drainage yielded hemorrhagic fluid, prompting further workup to identify a vascular bleeding source.Contrast-enhanced CT and CT angiography identified a pseudoaneurysm originating from the right ninth intercostal artery, and selective catheter angiography confirmed active extravasation from the lesion.Transcatheter arterial embolization successfully achieved hemostasis.Pleural-fluid bacterial and fungal cultures returned negative; however, an infectious etiology and underlying vascular disorders could not be completely excluded.As no traumatic or iatrogenic precipitating factor was identified, the lesion was categorized as non-traumatic and non-iatrogenic with undetermined etiology.At 1-month follow-up, the patient remained asymptomatic, and CT demonstrated ongoing resolution of the hemothorax. Conclusions:This case report shows that vascular etiologies of hemothorax, despite their low prevalence, must be included in the differential diagnosis for patients displaying an atypical clinical trajectory, especially when hemorrhagic pleural effusion develops following an initial clinical picture mimicking pulmonary infection.Timely implementation of contrast-enhanced CT, angiography, and endovascular embolization is pivotal to achieving definitive diagnosis and optimal therapeutic outcomes.