People with
psoriasis are also more likely to develop iritis especially people with
arthritis and psoriasis. People with inflammatory bowel disease also
develop iritis. The eye disease associated with Crohn's disease
is thought to be worse than the eye disease associated with ulcerative
colitis. The links between all these conditions is thought to be
genetic as relatives of people with AS are more likely to develop psoriasis,
inflammatory bowel disease or iritis even if their AS relative does
not have these conditions.
Bowel inflammation
is thought to be the trigger for both iriitis and AS.
Iritis
occurring when a person has inflammatory bowel disease or arthritis
with psoriasis (ie psoriatic arthritis) may be in both eyes, may be
slow to develop and may last longer.
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Who
is likely to get iritis ?
People
with AS inflammation in joints other than the spine (ie in the hip,
knee, feet, hands, shoulder etc) are more likely to develop iritis.
Iritis
is the most common additional condition associated with ankylosing spondylitis,
affecting between 40 people per 100 with ankylosing spondylitis.
What
is known about the genetics :
Many genes
control diseases like ankylosing spondylitis. A combination of
several genes interact with each other to deal with outside attack (such
as bacteria) from the environment. The gene HLA B27 is involved
in defending the body from outside attack of virus and bacteria. This
gene is very strongly linked to getting ankylosing spondylitis and getting
iritis. However, it is not the only gene because only 5-7 in 100 people
with the HLA B27 gene develop ankylosing spondylitis. Looking at people
who have got inflammatory bowel disease has shown another gene (called
NOD2) in a completely different area of the DNA which is involved in
other conditions like rheumatoid arthritis, psoriasis and crohns disease.
This gene could also be important in people who develop iritis. This
gene is also involved in defending the body from outside attack. There
are probably a number of genes which interact with each other to bring
about inflammation in the joint and eye (and bowel and skin). Further
work to identify these genes will greatly help our understanding and
ability to treat these conditions.
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What
drugs are used for iritis ? :
As our
understanding of the chemicals responsible for iritis improves, we can
begin to consider ways of targeting specific parts of the immune system.
Currently corticosteriod is used, but this is a steroid and so can not
be used in the long term without side effects. A new drug called anti-TNF
which targets a specific chemical involved in inflammation has been
shown to have an effect on iritis (as well as rheumatoid arthritis,
ankylosing spondylitis, bowel disease and psoriasis). However there
have been few studies examining this new drug in iritis. There are different
forms of the drug (different companies making the anti-TNF) and one
may be better than the other at treating iritis.
In
summary :
Iritis
is inflammation in the eye which commonly occurs in people with ankylosing
spondylitis. Progress has been made in understanding iritis and
drugs which may be used to treat the condition.
References
:
Tammy Marin
et al. Anterior uveities : current concepts of pathogenesis and interactions
with the spondyloarthropathies. Current Opinion in Rheumatology 2002;
14: 337-341]
Calin A
and Taurog J. The spondylarthritides. Oxford University Press 1998.
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