Marfan syndrome is the systemic disease most commonly associated with subluxated lenses. The syndrome consists of abnormalities of the cardiovascular, musculoskeletal, and ocular systems. It is inherited as an autosomal dominant trait, but family history is negative in 15% of cases. Marfan syndrome is caused by mutations in FBN1, which provides instructions for making the protein fibrillin-1, the major constituent of extracellular microfibrils. Affected patients are characteristically tall, with long limbs and fingers (arachnodactyly) (Fig 23-9); loose, flexible joints; scoliosis; and chest deformities. Cardiovascular abnormalities are a source of significant mortality and manifest as enlargement of the aortic root, dilation of the descending aorta, dissecting aneurysm, and floppy mitral valve. The life expectancy of patients with Marfan syndrome is about half that of the normal population.
A, Ectopia lentis et pupillae. B, Ultrasonography shows a membrane posterior to the iris attaching at the pupil margin.
(Part A reproduced from Byles DB, Nischal KK, Cheng H. Ectopia lentis et pupillae. A hypothesis revisited. Ophthalmology. 1998;105(7):1331–1336. Part B courtesy of Ken K. Nischal, MD.)
Figure 23-9 Long, slender digits in a patient with Marfan syndrome.
(Reproduced with permission from Lueder GT. Pediatric Practice: Ophthalmology. New York: McGraw-Hill Education; 2010: 222.)
Ocular abnormalities occur in more than 80% of affected patients, with lens subluxation being the most common (Fig 23-10). In approximately 75% of cases, the lens is subluxated superiorly. Typically, the zonules that are visible are intact and unbroken. Examination of the iris usually shows iridodonesis and may reveal transillumination defects near the iris base. The pupil is small and dilates poorly. The corneal curvature is often decreased. The axial length is increased, and affected patients are frequently myopic. Retinal detachment can occur spontaneously, usually in the second and third decades of life.
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.