Fibrillin and glycoprotein make up the microfibrillar system of the extracellular matrix. Fibrillin is found in corneal basement membrane, zonular fibers of the lens and capsule, and sclera. The syndrome is caused by mutations in the FBN1 gene, which encodes fibrillin-1 and maps to 15q21.1.
Figure 8-10 Slit-lamp photograph from a patient with Marfan syndrome, showing superior displacement of the lens. Note the stretched zonular fibers (arrow).
(Courtesy of Stephen E. Orlin, MD.)
Defects in fibrillin synthesis lead to thinning of the sclera (blue sclera), subluxation of the lens, and flattening of the cornea. Open-angle glaucoma and cataract occur at a higher rate and at an earlier age than in the population without Marfan syndrome. Megalocornea and keratoconus are uncommon, but excessive flattening, in the range of 35 diopters (D), occurs in up to 20% of patients.
Cardiac evaluation is typically considered, given that premature mortality is associated with aortic complications. Treatment of lens subluxation may require the use of advanced cataract surgery techniques such as capsular tension rings or scleral fixation; in severe cases of subluxation, a pars plana approach may be a better way to safely remove the lens. BCSC Section 11, Lens and Cataract, discusses the lens subluxation caused by Marfan syndrome and its treatment.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.