Abstract Introduction Pulmonary arteriovenous malformations (PAVMs) are rare vascular anomalies in which abnormal direct communications form between pulmonary arteries and veins without intervening capillaries. These lesions result in right-to-left shunting that can cause persistent hypoxemia and paradoxical embolism. Localized or multiple PAVMs are relatively well documented, and transcatheter embolization or surgical resection is considered standard therapy. However, diffuse PAVMs, characterized by innumerable small malformations distributed throughout both lungs, are extremely rare, and their optimal management remains uncertain. We report the clinical features, treatments, and outcomes of five patients with diffuse PAVMs treated at our institution. Case Series Between 2016 and 2025, five patients aged 18-37 years (two males, three females) were diagnosed with diffuse PAVMs. Chest imaging revealed bilateral diffuse multiple nodular or micronodular opacities in all cases. Three patients had coexisting hereditary hemorrhagic telangiectasia (HHT), underscoring the strong association between HHT and PAVMs. Resting oxygen saturation on room air ranged from 70% to 90%, and pulmonary shunt fractions were between 22.9% and 56.7%, indicating substantial impairment of gas exchange. Two patients underwent coil embolization, receiving 15 and 4 sessions, respectively. Although technical occlusion was achieved, recanalization occurred in both, and hypoxemia persisted without improvement. Surgical resection was not feasible due to the widespread bilateral distribution of lesions. Lung transplantation was considered for all patients, and one ultimately underwent transplantation. Following the procedure, the patient was liberated from home oxygen therapy and demonstrated marked improvement in arterial oxygenation and activities of daily living. Discussion This case series highlights the limitations of conventional interventions in diffuse PAVMs. While embolization is the first-line treatment for focal lesions, it was ineffective in our patients with diffuse disease, even after repeated procedures. In contrast, lung transplantation provided dramatic clinical improvement, suggesting its potential as a definitive therapy for diffuse PAVMs. Importantly, one patient experienced a paradoxical embolic event during follow-up, confirming that right-to-left shunting carries a significant risk of severe, life-threatening complications despite supportive care. These findings indicate that diffuse PAVMs should be approached as high-risk conditions requiring careful monitoring and early referral to specialized centers capable of lung transplantation. Coil embolization showed limited efficacy, whereas lung transplantation resulted in substantial clinical benefit and improved quality of life. Given the persistent risk of hypoxemia and paradoxical embolism, a comprehensive strategy that incorporates early consideration of lung transplantation is essential in the management of diffuse PAVMs. This abstract is funded by: None
Ebihara et al. (Fri,) studied this question.