Marfan Syndrome
Marfan syndrome is an inheritable disorder of connective tissue
(which adds strength to the body's structures) that affects the skeletal system, cardiovascular
system, eyes, and skin
Information about Marfan Syndrome
Marfan syndrome is known to be a dominant genetic disorder, which means that a person
needs to inherit only one defective gene in order to actually have the syndrome. In
addition to those cases of Marfan's which are clearly inherited, 20% of all Marfan's
patients have no family history of the syndrome. It is believed that these patients have
undergone a spontaneous genetic mutation leading to the syndrome. Interestingly, one risk
factor for Marfan syndrome (in a family where Marfan's is not already an inherited
disorder) is an elderly father. Marfan syndrome is said to have variable expression,
meaning that either all, or only a few, of the classic signs of Marfan syndrome may occur
in any given patient.
The biochemical problem which results in Marfan syndrome has not been well defined. The
group of tissues affected by Marfan syndrome are called the connective tissues. These are
tissues that are made of fibrous components, and they provide structural support for other
body tissues. Included in the group called connective tissues are bone, cartilage, fat
tissue, lymph tissue, and blood. The current belief is that the affected gene results in
an abnormality in a protein called microfibrillin; and this protein is responsible for
certain structural characteristics of connective tissue throughout the body.
Causes of Marfan Syndrome
Marfan syndrome is inherited as an autosomal dominant trait.
However, up to 30% of cases have no family history and are so called "sporadic"
cases. In sporadic cases, Marfan syndrome is believed to result from a spontaneous new
mutation.
Marfan syndrome is caused by mutations in the gene fibrillin-1. Fibrillin-1 plays an
important role as the “scaffolding” for elastic tissue in the body. Disruption
of such scaffolding (by mutations in fibrillin-1) thus results in changes in elastic
tissues, particularly in the aorta, eye, and skin. Mutations in fibrillin-1 also cause
overgrowth of the long bones of the body, resulting in the tall stature and long limbs
seen in Marfan patients.
How this overgrowth happens is not well understood. Marfan syndrome causes skeletal
defects typically recognized in a tall, lanky person with long limbs and spider-like
fingers (arachnodactyly), chest abnormalities (pectus excavatum or pectus carinatum),
curvature of the spine, and a particular set of facial features, including a highly arched
palate and crowded teeth.
Common eye problems are nearsightedness and dislocation of the lens of the eye.
The most significant of the defects in the syndrome are cardiovascular abnormalities,
which may include enlargement (dilatation) of the base of the aorta (aortic root), with
aortic regurgitation, and prolapse of the mitral valve. Affected people may develop
a dissecting aortic aneurysm.
Symptoms of Marfan syndrome
- Family history of Marfan syndrome
- Long, lanky frame
- Long, thin limbs
- Armspan significantly greater than body height
- Long, spidery fingers (arachnodactyly)
- Funnel chest (pectus excavatum) or pigeon breast (pectus carinatum)
- Scoliosis
- Visual difficulties
- Flat feet
- Learning disability/school problems
- Thin, narrow face
- Micrognathia (small lower jaw)
- Coloboma of iris
- Hypotonia
Diagnosis of Marfan Syndrome
A physical examination may show:
- Joint laxity (hypermobile joints)
- Myopia
- Dislocation of lens (ectopia lentis)
- Malformed cornea (flat)
- Retinal detachment
There may also be signs of:
- Dilated aortic root
- Aortic regurgitation
- Dissecting aortic aneurysm
- Mitral valve prolapse
- Other aortic aneurysms (thoracic or abdominal)
- Pneumothorax (collapsed lung)
The following tests may be performed:
- Echocardiogram
- Eye examination
- Fibrillin-1 mutation testing (in some individuals)
Treatment of Marfan Syndrome
There is no treatment for Marfan syndrome itself that can reverse the overall
connective tissue defects. Each manifestation of the syndrome needs to be addressed
individually (braces and physical therapy for the spinal curvature, occasional lens
removal for the lens dislocations, etc.). For girls who have grown quite tall, and have
cosmetic concerns about any further height, hormonal medications have been given to
initiate an early puberty, so that growth stops sooner and adult height is closer to
normal.
As stated previously, the most important problems to follow closely are those affecting
the heart and aorta. Some medications seem to be somewhat useful in slowing the stretching
of the aorta, although surgical replacement of part of the aorta is sometimes necessary,
as may be replacement of the defective mitral valve.
Prognosis of Marfan Syndrome
Careful monitoring of Marfan's patients, along with advice to avoid stress (physical,
emotional, and the stress of pregnancy) has helped to increase the expected life span of
Marfan's patients well beyond the age of 30 or 40 years, which was once the typical age of
death. |
