Immunohistochemical Abnormalities of Fibrillin in Cardiovascular Tissues in Marfan's Syndrome

Background: Molecular defects in the glycoprotein fibrillin are believed to be responsible for impaired structural integrity of cardiovascular, skeletal, and ocular tissues in Marfan's syndrome (MFS). Traditionally, excellent results have been achieved with the Bentall composite graft repair of aneurysms of the ascending aorta in MFS. However, because of the potential complications associated with prosthetic valves, there is growing interest in techniques that preserve the native aortic valve.

Methods: Between May 1994 and February 1995, 15 patients with a history of concomitant or remote aortic root aneurysms or dissection underwent operation for valvular heart disease. Specimens of aortic valve, ascending aortic wall, and mitral valve were obtained specifically to observe differences in fibrillin content and architecture between patients with (n = 9) and without (n = 6) MFS. In addition, control specimens of aortic valve, aortic wall, and mitral valve were obtained from 4 patients with isolated valvular or coronary artery disease but no evidence of connective tissue disorders or other aortic pathologic conditions. Fibrillin immunostaining using indirect immunofluorescence was used. Specimens were coded and graded by a blinded observer to determine quantity, homogeneity, and fragmentation of fibrillin.

Results: Observed fibrillin abnormalities in MFS and control patients were limited to the midportion (elastin-associated microfibrils) of the aortic valve, aortic wall, and mitral valve tissues. Fibrillin abnormalities of aortic valve, aortic wall, and mitral valve tissues were seen in all patients with MFS and were most severe in those older than 20 years. Similar fibrillin abnormalities of aortic valve and aortic wall specimens were observed in control patients more than 60 years old.

Conclusions: Even in the setting of a normal-appearing aortic valve, the current rationale for widespread use of valve-sparing repairs of aortic root aneurysms in patients with MFS and patients older than 60 years should be carefully reexamined in light of these findings.