What is a pulmonary artery aneurysm, and what is the major differential diagnosis?
A pulmonary artery aneurysm is defined as focal dilation of the pulmonary artery, involving all 3 layers of the arterial wall, to a diameter greater than 50% than that of the normal arterial caliber. Pulmonary artery aneurysms are rare, and etiologies may be congenital or acquired.
Among acquired causes, pulmonary artery aneurysms can be idiopathic, mycotic (i.e., infectious), or related to vasculitis (including Behçet’s syndrome, Hughes-Stovin syndrome, Marfan’s syndrome, Takayasu’s arteritis, or giant cell arteritis). Occasionally, chronic PE or severe pulmonary hypertension may lead to pulmonary arterial aneurysms.
Major differential diagnostic considerations include a pulmonary artery pseudoaneurysm (i.e., a contained rupture that involves less than all 3 arterial wall layers), and a pulmonary AVM. Pulmonary artery pseudoaneurysms are most often post-traumatic (particularly due to penetrating trauma), iatrogenic (such as from Swan-Ganz catheter placement), or mycotic in nature. A pulmonary artery pseudoaneurysm in the setting of pulmonary tuberculosis is called a Rasmussen aneurysm and is typically located adjacent to a chronic pulmonary parenchymal site of disease or adjacent to an area of pulmonary cavitation.