MARFAN'S SYNDROME
Marfan's syndrome is a genetic condition in which the connective tissue
of the body, which is an important structural component in all organs,
is abnormally weak and elastic. Marfan's is rare, affecting about 1 in
10,000 people, and variable in its features. It chiefly affects the eyes,
skeleton, heart and major blood vessels. The gene defect was identified
in 1990 and the abnormality of fibrillin, a connective tissue protein,
in 1991.
Cause:
Each human cell contains 23 pairs of chromosomes, one of each pair inherited
from the mother and one from the father. Each chromosome carries many genes
along its length and faults in genes are expressed as faults in the structure
of body chemicals. Marfan's syndrome is caused by a fault in a single dominant
gene, this implies that the disease is present although only one of a pair
of genes, either from the mother or the father, is affected. In about 25%
of people with Marfan's the fault in the gene has occurred spontaneously
before birth (a mutation), in 75% it is inherited. Males and females are
equally likely to be affected and, whether the gene was inherited or not,
have a 50% chance of passing on the abnormal gene, and so the condition,
to children of either sex. The gene for Marfan's syndrome lies on chromosome
15 and carries the code for the structure of fibrillin which is an important
part of collagen, the main component of connective tissue. Various different
mutations of the fibrillin gene have been found to cause Marfan's syndrome
and this may account for the various different physical manifestations.
Features of Marfan's syndrome:
People with Marfan's syndrome are tall and usually of very slim build
with especially long limbs, fingers and toes. They may have a high palate,
either prominence or depression of the breast bone and sometimes curvature
of the spine, especially in adolescence. They tend to have an early puberty
and stop growing early so the final height of children is seldom as tall
as seems likely through the school years. There is usually a degree of
hypotonia (floppiness) of the joints, often with "double jointedness".
These features may be apparent from birth or appear later in childhood.
In the eyes the most common feature is short sightedness but there may
be dislocation of the lens or a blue colour of the white of the eye. The
changes in the heart and blood vessels cause the most serious potential
complications. The heart valves may be abnormally floppy and this can cause
them to become leaky. There may also be widening of the aorta, the major
vessel carrying blood from the heart to the body, and this can develop
a tear in the wall (aortic dissection). Some children with Marfan's syndrome
have mild learning problems and there may also be a tendency to overactive
behaviour.
Diagnosis:
Many people show physical features similar to those of Marfan's syndrome
and, unless there is a clear family history, it can be difficult to confirm
or refute the diagnosis. It is not yet generally possible to make a definite
diagnosis by examination of the genes but this will no doubt become routine
as knowledge advances.
Treatment:
It is doubly important that people with Marfan's do not smoke because
this further damages collagen tissue. Although there is no curative or
specific treatment much can be done to assist with the correction of any
visual problems, the development of strength and movement skills, the prevention
of progressive skeletal abnormality and the early detection and possible
prevention (using beta blockers, a group of drugs which reduce the heart
impulse) of progressive dilatation of the aorta. If progressive aortic
dilatation or dissection does occur this section may sometimes need to
be replaced surgically. Affected people and their families need to be fully
informed about the condition.
Outlook:
In spite of the rather daunting list of possible complications it is
important to appreciate that most people with Marfan's syndrome live full
lives with few restrictions. Life expectancy is more than 60 years and
improving all the time with better treatment. The Marfan Association, 6
Queens Rd, Farnborough, Hants GU14 6DH (01252-547441) is an excellent source
of information and support for families. NDB |
