Distinct patterns of vascular failure in COL1A1-associated osteogenesis imperfecta and FBN1-associated Marfan syndrome

Introduction Heritable connective tissue disorders are an important cause of aortic disease; however, the mechanisms of vascular failure in genetically defined aortopathies remain incompletely understood. Methods We analyzed the clinical course, imaging findings, and histopathologic features of two patients with clinically and genetically characterized connective tissue disorders: COL1A1-associated osteogenesis imperfecta and FBN1-associated Marfan syndrome. Results The COL1A1-associated patient developed multilevel arterial complications, including aortic regurgitation requiring aortic valve replacement at age 36, rupture of a dissected right common iliac artery in the same year, chronic type A aortic dissection requiring root, ascending, and arch replacement at age 54, and rupture of the infrarenal abdominal aorta at a diameter of only 30 mm. The FBN1-associated patient presented with type B aortic dissection at age 34 and subsequently developed progressive aneurysmal disease requiring staged thoracoabdominal replacement, total arch replacement for acute type A dissection, and aortic root replacement, followed by multiple peripheral vascular reconstructions. Histopathologic examination demonstrated valvular myxomatous degeneration in both cases. The aortic wall in both patients showed medial degeneration with fragmentation of elastic fibers. In addition, the COL1A1-associated patient demonstrated abdominal aortic wall thinning, with a minimum thickness of 1.25 mm. Conclusions These two patients exhibited contrasting longitudinal vascular courses despite some overlapping histopathologic findings. The COL1A1-associated OI patient experienced rupture of a dissected infrarenal aortic segment, whereas the FBN1-associated Marfan patient experienced repeated dissections followed by progressive vascular dilatation and multiple surgical reconstructions. These observations are descriptive and do not establish genotype-specific patterns or mechanisms of vascular failure.