We report a rare case of idiopathic pulmonary artery aneurysm (PAA) in a 56-year-old woman without any causative conditions, such as congenital heart disease, inflammation, pulmonary artery hypertension, or systemic vasculitis. She presented with sudden back pain, and examination revealed the PAA. She electively underwent resection of the aneurysm and graft replacement. Pathology examination revealed cystic medial necrosis, which was considered the underlying pathology of the aneurysm.
© The Japanese Association for Thoracic Surgery 2011