The major theories about the causes of multiple sclerosis (MS) include the following:|
It's now generally accepted that MS involves an autoimmune process, which is an abnormal
response of the body’s immune system that is directed against the myelin in the
central nervous system (CNS). The exact antigen, or target that the immune cells
are sensitized to attack, still remains unknown. In recent years, however, researchers
have been able to identify which immune cells are mounting the attack, some of
the factors that cause them to attack, and some of the sites, or receptors, on
the attacking cells that appear to be attracted to the myelin to begin the
destructive process. Ongoing efforts to learn more about the autoimmune process
in MS (what sets it in motion, how it works, and how to slow or stop it) are
bringing everyone closer to understanding the cause of MS.
MS is known to occur more frequently in areas that are farther from the equator.
Epidemiologists (scientists who study disease patterns) are looking at many
factors, including variations in geography, demographics (age, gender, and
ethnic background), genetics, infectious causes, and migration patterns, in an
effort to understand why. Studies of migration patterns have shown that people
born in an area of the world with a high risk of MS who then move to an area
with a lower risk before the age of 15, acquire the risk of their new area. Such
data suggest that exposure to some environmental agent that occurs before
puberty may predispose a person to develop MS later on.
Some scientists think the reason may have something to do with vitamin D, which
the human body produces naturally when the skin is exposed to sunlight. People
who live closer to the equator are exposed to greater amounts of sunlight
year-round. As a result, they tend to have higher levels of naturally-produced
vitamin D, which is thought to have a beneficial impact on immune function and
may help protect against autoimmune diseases like MS.
Other scientists study MS clusters—which are defined as higher-than-expected
numbers of cases of MS that have occurred over a specific time period and/or in
a certain area. These clusters are of interest because they may provide clues to
environmental (such as environmental and industrial toxins, diet, or trace metal
exposures) factors that might cause or trigger the disease. So far, cluster
studies have not produced clear evidence for the existence of any triggering
factor or factors in MS.
Since initial exposure to numerous viruses, bacteria and other microbes occurs
during childhood, and since viruses are well recognized as causes of
demyelination and inflammation, it is possible that a virus or other infectious
agent is the triggering factor in MS. More than a dozen viruses and bacteria,
including measles, canine distemper, human herpes virus-6, Epstein-Barr, and
Chlamydia pneumonia have been or are being investigated to determine if they are
involved in the development of MS, but none have been definitively proven to
While MS is not hereditary in a strict sense, having a first-degree relative
such as a parent or sibling with MS increases an individual's risk of developing
the disease several-fold above the risk for the general population. Studies have
shown that there is a higher prevalence of certain genes in populations with
higher rates of MS. Common genetic factors have also been found in some families
where there is more than one person with MS. Some researchers theorize that MS
develops because a person is born with a genetic predisposition to react to some
environmental agent that, upon exposure, triggers an autoimmune response.
Sophisticated new techniques for identifying genes may help answer questions
about the role of genes in the development of MS.
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As with many things in life, was it the environment or your genetics that
determined who you've become - MS or not. Some may argue that it has to be one
or the other, but it's most likely a combination of both and probably many other
factors. So let's begin and try to gain some insight on how this disease takes
hold and begins on its path of destruction.
As with any disease, why does one person get it and another doesn't? Let's take
a disease such as cancer, how does it choose so precisely at times and so
randomly at others? A smoker may never develop lung cancer and then someone that
never touched a cigarette nor was ever near second-hand smoke may die of lung
cancer at 50 years of age - how and why can this be? What if the last two people
mentioned where twins, would that make and difference?
Just as your genes help determine how you respond to certain medicines, your
genetic code can also affect your susceptibility to illness. Why is it that two
people with a similar lifestyle and a nearly identical environment can have such
different propensities to getting sick? Many factors contribute, including diet,
but researchers believe that an important component of disease risk is the
genetic variability of people's reactions to chemicals in the environment.
Now what if there were two identical twins, their genetic structure would
basically be the same, and they grew up being exposed to nearly the same
environment. What if one of these twins got MS and the other got Parkinson's,
what determines this?
Genetic variation could be a factor due to a difference in deoxyribonucleic acid
(DNA) molecules. Those molecules, called nucleotides, are adenine, cytosine,
guanine, and thymine (A,C,G,T) and are strung together in long chains called
sequences. The occasional single-letter differences that distinguish DNA among
people are called single-nucleotide polymorphisms (SNPs).
The incidence and prevalence of MS is it is the most common neurological cause
of debilitation in young people and affects about 500,000 people in the United
States. Worldwide, the incidence is approximately 0.1% of the total population.
Northern United States and the northern Europe have the highest prevalence, with
more than 30 cases per 100,000 people.
A person's chances of developing MS increase if they have a relative with MS.
It's believed that certain genetic combinations increase the likelihood of a
person to develop MS. It's felt my most that this increase in risk isn't high
enough to call MS a "genetic disease". Instead, it seems that genes are one of
many factors that determine a person's risk for MS.
There is a higher rate of MS in family members. The world population in general has
approximately a 0.25% risk of developing MS, while an immediate family member of
someone with MS, such as a child or sibling, has a 3 to 5% chance of developing MS.
The fact is that identical twins – who share identical genes – don't always get MS,
and that the vast majority of people with MS don't have another family member with
the disease. This demonstrates that while genes may play an important role, other
environmental factors must be present as well.
The chances of developing MS in the United States are as follows:
||0.1% (1 in 750) if you have no relatives with MS
(The General Population).
||1% (1 in 100) for second-degree
relative (grandparent, aunt, uncle) with MS.
||2.5 to 5% for first-degree relatives (children, siblings or non-identical twins)
||25% (1 in 4) for an identical twin with MS.
This section will look into the many different factors may have an impact on MS.
What could be the trigger that starts it up one day and then the attacks begin?
This is a question that know body knows the answer to, because if anyone did, we
would be so much closer to a cure or at least preventing MS from striking anyone
Whatever the cause is, the effect is MS. It's also important to look at how and
why MS differs from so many other conditions as well as the similarities.