Science_Illustrated_Australia_-_Issue70_2019

Sclerosis is

in the genes

Scientists do not yet know why the immune system

attacks the body’s healthy cells. But according to

statistics, the genes play a central role.

people are diagnosed with sclerosis annually, the majority

of whom live in Northern and Western Europe.

of sclerosis patients

also have a relative

with the disease.

4 IN 100,000

85%

of all

cases are

characterised

by severe and

sudden attacks on different parts

of the central nervous system.

4%

is the risk of

developing

multiple

sclerosis

if one of your

parents has

the disease.

15-20%

SHU

TTE

RST

OC

K

Injuries slow down the signal

3

The signal can no longer jump between
the myelin sheaths, making nerve cells
communicate more slowly. In addition,
the cell is more exposed without insulation and
could end up being completely destroyed.

ATTA

CK

pearls on a string, helping the nerve cells
send electrical signals to each other quickly
and efficiently. Without the sheaths, the
nerve cells communicate more poorly, and
the fibre threads will often end up being de-
stroyed to such an extent that the nerve cell
cannot communicate with its neighbouring
cells at all. This can influence not only our
ability to think and understand but even our
ability to move, so that in particularly severe
cases the injuries cause paralysis.
Scientists do not yet know exactly why
the immune system attacks the body’s
healthy cells, but research indicates that
autoimmune diseases such as sclerosis
might develop after an infection with a virus
or bacteria. But even when the harmful
organism, virus or bacterium has been
removed, the immune system continues the

killing – now targeting the oligodendrocytes,

perhaps because their chemistry is some-

how similar to the chemistry of bacteria

and viruses. That is probably why multiple

sclerosis develops, but nobody knows which

viruses or bacteria trigger the disease.

Among the suspects that scientists have

identified are herpes viruses 1 and 2,

varicella-zoster virus (which causes chicken-

pox), cytomegalovirus, Epstein-Barr virus,

and the measles virus. Several of those are

relatively common virus types with which

many of us have been infected at some point

without developing multiple sclerosis. But

genes also play a role, and many patients

with multiple sclerosis have the HLA-class II

tissue type, which is linked with autoim-

mune diseases in general. Genetics might

also contribute to explaining why the dis-

ease is more common in some regions of the

world – such as Northern Europe, where

there is both a high rate of the above virus

types and people with sclerosis genes. In

Norway and Finland, 177 and 155 in 100,000

people have multiple sclerosis, far above

nations further south such as Bulgaria,

where the rate is 62 in 100,000 people. The

Sámi people who live in Northern Norway

and Finland develop the disease far more

rarely than their fellow countrymen, with a

rate of only 30-50 in 100,000 people. This

indicates that it is not solely environmental

factors that trigger the disease.

Also notable is that parents can pass the

disease on to their children. If one parent

has multiple sclerosis, the risk of the child

developing the disease is 4%. That is 20-50

times higher than the risk for the general

Destroyed nerve cell

Neighbouring cell

scienceillustrated.com.au | 59