Latent Vasculopathy of a Peripheral Pulmonary Artery in FBN1-Related Marfan Syndrome.

Marfan syndrome (MFS) is a hereditary connective tissue disorder characterized by cardiovascular and skeletal abnormalities. While cardiovascular pathology is well described, the microscopic features of peripheral vasculature remain poorly characterized. We report a case of perioperative pulmonary arterial rupture in a patient with FBN1-related MFS. A 17-year-old woman underwent bullectomy for spontaneous pneumothorax. Although the procedure was initially uneventful, unexpected bleeding developed beneath the staple line immediately after reinflation for the post-bullectomy air-leak test, necessitating additional wedge resection. Histologically, a ruptured pulmonary arterial branch was identified adjacent to the staple line. Patchy foci of hyperacute vascular injury with hemostatic plugs were identified on the luminal surface, and the surrounding airspaces were filled with fresh blood. The affected arterial wall showed mucoid extracellular matrix accumulation and disorganization of smooth muscle bundles. Furthermore, the medial layer demonstrated an aberrant distribution of elastic fibers, deviating from the normal architecture of muscular arteries. These findings highlight previously underrecognized microscopic features of peripheral arterial involvement in FBN1-related MFS, characterized by latent structural fragility associated with abnormal vascular patterning. Surgery-associated hemodynamic changes, including perioperative reinflation for an air-leak test, which would be tolerated under normal conditions, may precipitate vascular injury and rupture.