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Marfan Syndrome

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Chromosones

Nature of the Genetic Difficulty


It is inherited as a dominant trait. It is carried by a gene called FBN1, which encodes a connective protein called fibrillin-1. People have a pair of FBN1 genes. Because it is dominant, people who have inherited one affected FBN1 gene from either parent will have Marfan's.

Marfan syndrome has a range of expressions, from mild to severe. The most serious complications are defects of the heart valves and aorta. It may also affect the lungs, eyes, the dural sac surrounding the spinal cord, skeleton and the hard palate.
In addition to being a connective protein that forms the structural support for tissues outside the cell, the normal fibrillin-1 protein binds to another protein, transforming growth factor beta (TGF-β). TGF-β has deleterious effects on vascular smooth muscle development and the integrity of the extracellular matrix. Researchers now believe that secondary to mutated fibrillin there is excessive TGF-β at the lungs, heart valves, and aorta, and this weakens the tissues and causes the features of Marfan syndrome. Since angiotensin II receptor blockers (ARBs) also reduce TGF-β, they have tested this by giving ARBs (losartan, etc.) to a small sample of young, severely affected Marfan syndrome patients. In some patients, the growth of the aorta was indeed reduced.

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Basis Facts of Disease

Marfan syndrome (also called Marfan's syndrome) is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers. Marfan syndrome is named after Antoine Marfan, the French pediatrician who first described the condition in 1896. The gene linked to the disease was first identified by Francesco Ramirez in 1991.

People with Marfan syndrome are usually tall with long, thin arms and legs and spider-like fingers -- a condition called arachnodactyly. When they stretch out their arms, the length of their arms is much greater than their height.
Other symptoms include:
  • A chest that sinks in or sticks out -- funnel chest (pectus excavatum) or pigeon breast (pectus carinatum)
  • Flat feet
  • Highly arched palate and crowded teeth
    Hypotonia
  • Joints that are too flexible
  • Learning disability
  • Movement of the lens of the eye from its normal position (dislocation)
  • Nearsightedness
  • Small lower jaw (micrognathia)
  • Spine that curves to one side (scoliosis)
  • Thin, narrow face

Prognosis

Heart-related complications may shorten the lifespan of people with this disease. However, many patients survive well into their 60s. Good care and surgery may extend the lifespan further.

Sources Cited

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001455/
http://en.wikipedia.org/wiki/Marfan_syndrome