We’re now going to look
at autoimmune disease.
Autoimmune disease is a pathological
reaction against a normal body component.
Around about 5% of people
develop an autoimmune disease.
Overall, autoimmune diseases occur
more commonly in females than males.
Perhaps most extreme example is systemic lupus erythematosus,
where the ratio of females to males is around about ten to one.
Usually the dominance in females over
males is somewhat less than that.
And sometimes autoimmune diseases are
more common in males than females.
So for example, ankylosing spondylitis
is twice as common in males than females.
Autoimmune diseases can be either organ specific or systemic
depending on the location of the target autoantigen.
By far the vast majority of autoimmune
diseases are polygenic in nature.
That means many different genes
contribute towards their development.
Concordance rates in identical twins
is typically around about 30-50%.
What this tells us is that genetics
is very very important and plays
a major role, but non-genetic factors
must also be playing a role.
The non-genetic factors are not that well understood,
but may include infection, diet and stress.
Autoimmune disease develops typically in the
middle years of life, suggesting a breakdown in
immunological tolerance rather than initial failure
to actually establish immunological tolerance.
You can develop autoimmune disease
at any point in your life.
Young infants can develop
it, elderly can develop it.
But the most typical time is
in the middle years of life.
Autoimmune disease is usually
lifelong following onset.
Although, often with periods
of relative disease inactivity.
The severity of an autoimmune disease
can be influenced by pregnancy.