Contributor: Gordon K. Klintworth
Marfan syndrome is an inherited disorder of connective tissue with musculoskeletal, cardiovascular and ocular manifestations. It is one of the commonest connective tissue disorders. The syndrome has an autosomal dominant mode of inheritance, but almost 15% of cases occur sporadically. Two genetically distinct types are recognized: Marfan syndrome type I and Marfan syndrome type II. Most cases result from missense mutations in the FBN1 gene that encodes for defective fibrillin, other cases that lack ocular abnormalies have a mutation in the TGFBR2 gene. The cardinal features of the Marfan syndrome involve the eye as well as the cardiovascular and skeletal systems. The ophthalmologic manifestations include a developmental anomaly of the anterior chamber angle, spherophakia and ectopia lentis. A characteristic ocular abnormality in Marfan syndrome is ectopia lentis due to defective zonules and Marfan syndrome is the most frequent inherited disease causing ectopia lentis. Glaucoma most often results from a pupillary block from an ectopic lens with spherophakia, but another cause of glaucoma in Marfan syndrome is the developmental anomaly of the anterior chamber angle. The developmental anomalies in the anterior chamber angle in Marfan syndrome include numerous broad, fine iris processes that extend from the iris root to the various structures (anterior surface of the ciliary body, the scleral spur, the trabecular meshwork, and Schwalbe line), an elongated corneoscleral trabecular meshwork, a less prominent than normal uveal trabecular meshwork and scleral spur and a paucity of crypts in the anterior iris surface. Other ophthalmic manifestations include myopia, ocular enlargement, microphakia, staphyloma, retinal detachment, a thin blue sclera and keratoconus. Skeletal anomalies include kyphoscoliosis, pectus carinatum, and/or pectus excavatum. Affected persons tend to be tall with elongated scrawny limbs, and arachnodactyly. A shortened life time of persons with the Marfan syndrome is attributed to the cardiovascular manifestations. The joints are often hypermobile with redundant ligaments and capsules.The differential diagnosis of Marfan syndrome includes Beals syndrome.