[1] The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm.

Subluxation (partial dislocation) of the lens can be detected clinically in about 60% of people with Marfan syndrome by the use of a slit-lamp biomicroscope.

[19] Other signs and symptoms affecting the eye include increased length along an axis of the globe, myopia, corneal flatness, strabismus, exotropia, and esotropia.

[18] The most serious signs and symptoms associated with Marfan syndrome involve the cardiovascular system: undue fatigue, shortness of breath, heart palpitations, racing heartbeats, or chest pain radiating to the back, shoulder, or arm.

However, the major sign that would lead a doctor to consider an underlying condition is a dilated aorta or an aortic aneurysm.

[20] Because underlying connective tissue abnormalities cause MFS, the incidence of dehiscence of prosthetic mitral valve is increased.

Other possible pulmonary manifestations of MFS include sleep apnea[25] and idiopathic obstructive lung disease.

Dural ectasia that has progressed to this stage would appear in an MRI as a dilated pouch wearing away at the lumbar vertebrae.

[citation needed] Each parent with the condition has a 50% risk of passing the genetic defect on to any child due to its autosomal dominant nature.

[32] Marfan syndrome is caused by mutations in the FBN1 gene on chromosome 15,[33] which encodes fibrillin 1, a glycoprotein component of the extracellular matrix.

The extracellular matrix is critical for both the structural integrity of connective tissue, but also serves as a reservoir for growth factors.

[29] Elastic fibers are found throughout the body, but are particularly abundant in the aorta, ligaments and the ciliary zonules of the eye; consequently, these areas are among the worst affected.

A transgenic mouse has been created carrying a single copy of a mutant fibrillin-1, a mutation similar to that found in the human gene known to cause MFS.

Fibrillin-1 directly binds a latent form of TGF-β, keeping it sequestered and unable to exert its biological activity.

Although how elevated TGF-β levels are responsible for the specific pathology seen with the disease is not proven, an inflammatory reaction releasing proteases that slowly degrade the elastic fibers and other components of the extracellular matrix is known to occur.

[38][39] It has been shown that these people are also deficient in asprosin, a gluco-regulatory protein hormone which is the C-terminal cleavage product of profibrillin.

The levels of asprosin seen in these people were lower than expected for a heterozygous genotype, consistent with a dominant negative effect.

[41] However, Marfan syndrome is often difficult to diagnose in children, as they typically do not show symptoms until reaching pubescence.

The seven new criteria can lead to a diagnosis:[58][59] In the absence of a family history of MFS: In the presence of a family history of MFS (as defined above): The thumb sign (Steinberg's sign) is elicited by asking the person to flex the thumb as far as possible and then close the fingers over it.

The following are some of the disorders that can manifest as "marfanoid":[citation needed] There is no cure for Marfan syndrome, but life expectancy has increased significantly over the last few decades[when?]

Marfan syndrome is treated by addressing each issue as it arises and, in particular, preventive medication even for young children to slow progression of aortic dilation.

[18] Treatment of a spontaneous pneumothorax is dependent on the volume of air in the pleural space and the natural progression of the individual's condition.

[71][72] During pregnancy, even in the absence of preconception cardiovascular abnormality, women with Marfan syndrome are at significant risk of aortic dissection, which is often fatal even when rapidly treated.

[73] Prenatal testing can be performed in females with Marfan syndrome to determine if the condition has been inherited in their child.

[42] At 10 to 12 weeks of pregnancy, examining a piece of placental tissue through a test called chorionic villus sampling can be performed to make a diagnosis.

Today, cardiovascular symptoms of Marfan syndrome are still the most significant issues in diagnosis and management of the disease, but adequate prophylactic monitoring and prophylactic therapy offers something approaching a normal lifespan, and more manifestations of the disease are being discovered as more patients live longer.

[17] Marfan syndrome affects males and females equally,[76] and the mutation shows no ethnic or geographical bias.

[12][77] The gene linked to the disease was first identified by Francesco Ramirez at the Mount Sinai Medical Center in New York City in 1991.