Genetics The Basic Facts

“What makes people susceptible to
multiple sclerosis?” Most scientists and
physicians who have studied this question
are convinced that heredity—the genes we
inherit from our ancestors—is one factor.
In 1992, the Society began a major targeted
research initiative to search for the genes
that make people susceptible to developing
MS. Understanding how genes contribute
to determining who gets MS should
provide major clues to the cause, and may
point to ways of preventing and treating it.
Advances in the field of molecular genetics
offer hope that we will be able to answer
the question someday.
Two types of evidence support the
connection between genes and
susceptibility to MS:
The first comes from population studies.
People from diff erent ethnic groups
have different tendencies to develop MS.
It is most common among people of
Northern European ancestry, although
African Americans and Hispanics
develop MS as well. Other ethnic
groups—Inuits, African blacks, and
Southeast Asians—are much less likely
to have MS.
Th e second type of evidence comes
from studies of families in which MS
occurs more frequently than chance
would dictate. Th e average person in
the United States has about one chance
in 750 of developing MS. But relatives
of people with MS, such as children,
siblings or nonidentical twins, have a
higher chance—ranging from one in
100 to one in 40. Th e identical twin of
someone with MS, who shares all the
same genes, has a one in four chance of
developing the disease.
These facts tell us that genes are important
for determining who may get MS, but they
are not the whole story: the identical twin

“What makes people susceptible to Multiple Sclerosis?

Most scientists and physicians who have studied this question

are convinced that heredity—the genes we
inherit from our ancestors—is one factor.
In 1992, the Society began a major targeted
research initiative to search for the genes
that make people susceptible to developing
MS. Understanding how genes contribute
to determining who gets MS should
provide major clues to the cause, and may
point to ways of preventing and treating it.
Advances in the field of molecular genetics
offer hope that we will be able to answer
the question someday.
Two types of evidence support the
connection between genes and
susceptibility to MS:
Th e first comes from population studies.
People from different ethnic groups
have different tendencies to develop MS.
It is most common among people of
Northern European ancestry, although
African Americans and Hispanics
develop MS as well. Other ethnic
groups—Inuits, African blacks, and
Southeast Asians—are much less likely
to have MS.
The  second type of evidence comes
from studies of families in which MS
occurs more frequently than chance
would dictate. The average person in
the United States has about one chance
in 750 of developing MS. But relatives
of people with MS, such as children,
siblings or nonidentical twins, have a
higher chance—ranging from one in
100 to one in 40. The identical twin of
someone with MS, who shares all the
same genes, has a one in four chance of
developing the disease.
These facts tell us that genes are important
for determining who may get MS, but they
are not the whole story: the identical twin
of a person with MS would always get MS
if genes were the only factor involved.
In addition to genes, other factors—
perhaps exposure to germs or viruses—
play a part in causing MS. That is why
scientists say that MS is not
directly inherited.
Genetic factors
determine who is
susceptible to the
unknown outside
trigg of a person with MS would always get MS
if genes were the only factor involved.
In addition to genes, other factors—
perhaps exposure to germs or viruses—
play a part in causing MS. That is why
scientists say that MS is not
directly inherited.
Genetic factors
determine who is
susceptible to the
unknown outside
trigg