A 51-year-old man presented with frequent nosebleeds, telangiectasias on the lips, and a family history of brain abscess in his mother at age 50 and sudden death in his sister at age 21. Genetic testing identified a mutation of the ALK-1 gene, confirming the diagnosis of hereditary hemorrhagic telangiectasia (HHT) type 2. Although no arteriovenous malformations (AVMs) were found in the lung, liver, or brain, contrast-enhanced computed tomography showed mediastinal vascular abnormalities (Figure 1). Subsequent bronchial angiography revealed a 13-mm aneurysm in the proximal left bronchial artery and dilated bilateral bronchial arteries meandering through the mediastinum and draining into the pulmonary veins by means of capillary blushes (Figure 2). Pulmonary vasodilators, macitentan and sildenafil, were started owing to pulmonary hypertension on right heart catheterization; however, his AVMs were placed on observation, given that any local vascular intervention might alter the pulmonary hemodynamics and thus possibly worsen the shunt and increase the risk of rupture. Fortunately, the mediastinal AVMs have remained stable on computed tomography over the past 6 years.

Figure 1. (A) Axial chest computed tomography (CT) demonstrating a dilated pulmonary artery and numerous abnormal blood vessels in the middle mediastinum. (B) Three-dimensional reconstruction of the CT showing dilated left (black arrows) and right (white arrows) bronchial arteries running tortuously in the mediastinum. An aneurysm in the proximal left bronchial artery is indicated by black arrowheads in (A) and (B).

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Figure 2. (A–C) Delayed arterial phases of selective bronchial angiography showing one right (A) and two left (B and C) dilated bronchial arteries running tortuously in the mediastinum. A 13-mm aneurysm (arrowhead in B) is present at the beginning of the left bronchial artery. (D) Venous phase right bronchial angiogram showing a distal capillary blush (arrows) draining into the right pulmonary vein.

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Here, we present a rare but clinically important case of HHT2 with diffuse AVMs directly communicating between the bronchial arteries and pulmonary veins. Unlike bronchopulmonary AVMs reported previously (1–4), the AVMs in this case were primarily central and diffuse, supplied only from the systemic circulation, and not caused by the development of collateral circulation after pulmonary AVM embolization. Because it is a left-left shunt, we should be aware that this atypical AVM cannot be detected with the recommended screening test, transthoracic contrast echocardiography (5), and can result in rupture rather than decreased oxygenation. In addition, because pulmonary hypertension in patients with HHT may be associated with an ALK-1 gene anomaly and partially caused by remodeling and occlusion of the small pulmonary arteries (6), it could be speculated that hypertrophy of the bronchial circulation might occur as collateral compensation for the reduced pulmonary arterial flow.