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Fraternal twins, however, share
only some of the same genes. In identical twins, chances
are three times greater that psoriasis will be present
in both siblings, compared to fraternal twins. Even
if multiple genes are required to cause psoriasis, this
finding is important in indicating a genetic basis.
Triggers
While psoriasis has a definite
genetic component, environmental factors also play a
key role in the onset and severity of disease. Patients
with psoriasis might note that they experience a worsening
or flare of their disease in response to external or
internal factors. There are many such factors that can
indirectly trigger the onset of psoriasis or aggravate
it in someone already affected. These include:
stress
skin injury (Koebner phenomenon)
medications
climate
infection
Stress
Excessive stress can play a role
in making psoriasis worse. Stress is a constant feature
of modern life, but major events that cause significant
stress can cause a flare in a patient's psoriasis. For
example, sickness, job pressures, the death of a loved
one or relationship break-ups are all events that may
cause a flare in psoriasis.
Stress is not the root cause of
psoriasis, but it can aggravate an existing condition
or lead to the development of psoriasis in predisposed
people. Stress can also delay the healing process. In
a study at the University of Manchester (U.K.), it was
found that psoriasis patients who worry excessively
might experience slower responses to phototherapy than
those who do not worry a great deal. The findings revealed
that those patients classified as "high-level"
worriers took about twice as long to improve than those
who were "low-level" worriers.
Skin injury (Koebner
phenomenon)
Psoriasis can occur after injury
to the skin. This is known as the "Koebner phenomenon."
Any picking, scratching or injuries from cuts, burns
or bruises can be responsible for triggering the development
of new psoriatic lesions at the exact site of injury.
This could partly explain why psoriasis can be present
over the elbows and knees where friction and trauma
are frequent, or after surgery, at the site of a surgical
scar.
Medications
Certain medications have been
related to aggravating psoriasis including antimalarials,
beta-blockers, lithium and interferons. Sudden discontinuation
of treatment with cyclosporine, systemic corticosteroids,
or a new biologic agent called efalizumab is known to
cause psoriasis flares in some patients. Medications
that may induce or worsen psoriasis include:
Beta-blockers (used to treat high
blood pressure)
propranolol
sotalol HCI
atenolol
metoprolol
acebutolol
Lithium
Carbonate (used to treat manic-depressive disorder)
Antimalarials (used to treat malaria
initially, and now other conditions such as lupus)
quinacrine
chloroquine
hydroxychloroquine
Interferons
(used to treat hepatitis C, multiple sclerosis, cancer)
interferon _
interferon _
Climate
Many patients will experience
changes in their condition in different seasons, and
typically report that cold weather can cause worsening
of their psoriasis, while sunlight is usually beneficial.
Other
Other factors that may contribute
to psoriasis onset or worsening include smoking (with
pustular psoriasis) and alcohol.
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