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BioTech Navigator, January 2000
creased activity by T cells in the skin.
These T cells trigger the inflamma-
tion and excessive skin cell reproduc-
tion commonly seen in people with
psoriasis.
In about one-third of the cases,
psoriasis is inherited. Researchers are
studying large families affected by
psoriasis to identify a gene or genes
that cause the disease.
People with psoriasis may notice
that there are times when their skin
worsens, then improves. Conditions
that may cause flare-ups include
changes in climate, infections, stress,
and dry skin. Also, certain medicines,
most notably beta-blockers, which are
used to treat high blood pressure, and
lithium or drugs used to treat depres-
sion, may trigger an outbreak or
worsen the disease.
How Is Psoriasis Diagnosed?
Doctors usually diagnose psoriasis
after a careful examination of the
skin. However, diagnosis may be diffi-
cult because psoriasis can look like
other skin diseases. A pathologist may
assist with diagnosis by examining a
small skin sample (biopsy) under a
microscope.
There are several forms of psoria-
sis. The most common form is plaque
psoriasis (its scientific name is psoria-
sis vulgaris). In plaque psoriasis, le-
sions have a reddened base covered by
silvery scales. Other forms of psoria-
sis include Guttate psoriasis--Small,
drop-like lesions appear on the trunk,
limbs, and scalp. Guttate psoriasis is
most often triggered by bacterial in-
fections (for example, Streptococcus).
Pustular psoriasis--Blisters of nonin-
fectious pus appear on the skin. Medi-
cations, infections, emotional stress,
or exposure to certain chemicals may
trigger attacks of pustular psoriasis.
Pustular psoriasis may affect either
small or large areas of the body. In-
verse psoriasis--Large, dry, smooth,
vividly red plaques occur in the folds
of the skin near the genitals, under
the breasts, or in the armpits. Inverse
psoriasis is related to increased sensi-
tivity to friction and sweating and
may be painful or itchy. Erythroder-
mic psoriasis--widespread reddening
and scaling of the skin is often accom-
panied by itching or pain. Severe
sunburn, use of oral steroids (such as
cortisone), or a drug-related rash may
precipitate Erythrodermic psoriasis.
What Treatments Are
Available for Psoriasis?
Doctors generally treat psoriasis
in steps based on the severity of the
disease, the extent of the areas in-
volved, the type of psoriasis, or the
patient's responsiveness to initial
treatments. This is sometimes called
the "1-2-3" approach. In step 1, medi-
cines are applied to the skin (topical
treatment). Step 2 focuses on light
treatments (phototherapy). Step 3 in-
volves taking medicines internally,
usually by mouth (systemic treat-
ment).
Over time, affected skin can be-
come resistant to treatment, especially
when topical corticosteroids are used.
Also, a treatment that works very well
in one person may have little effect in
another. Thus, doctors commonly use
a trial-and-error approach to find a
treatment that works, and they may
switch treatments periodically (for
example, every 12 to 24 months) if
resistance or adverse reactions occur.
Treatment depends on the location of
lesions, their size, the amount of the
skin affected, previous response to
treatment, and patients' perceptions
about their skin condition and prefer-
ences for treatment. In addition, treat-
ment is often tailored to the specific
form of the disorder.
Treatments applied directly to the
skin are sometimes effective in clear-
ing psoriasis. Doctors find that some
patients respond well to sunlight, cor-
ticosteroid ointments, medicines de-
rived from vitamin D3, vitamin A
(retinoids), coal tar, or anthralin.
Other topical measures, such as bath
solutions and moisturizers, may be
soothing but are seldom strong
enough to clear lesions over the long
term and may need to be combined
with more potent remedies.
Ultraviolet (UV) light from the
sun causes the activated T cells in the
skin to die, a process called apoptosis.
Apoptosis reduces inflammation and
slows the overproduction of skin cells
that causes scaling. Short daily, non-
burning exposure to sunlight clears or
improves psoriasis in many people.
Therefore, sunlight may be included
among initial treatments for the dis-
ease. A more controlled form of artifi-
cial light treatment may be used in
mild psoriasis (UVB phototherapy) or
in more severe or extensive psoriasis
(psoralen and ultraviolet A [PUVA]
therapy).
For more severe forms of psoria-
sis, doctors sometimes prescribe medi-
cines that are taken internally. These
medicines are commonly used for
other autoimmune-related diseases
that function to suppress the immune
response. Familiar drugs such as
methotrexate and cyclosporine are
usually the first medicines of this
class prescribed. In the event that
these cannot be taken primarily due to
side effects, then less effective medi-
cines such as hydroxyurea, retinoids
(vitamin A-like compounds) or antibi-
otics are given. Antibiotics may be
employed when an infection, such as
Streptococcus, triggers the outbreak of
psoriasis, as in certain cases of guttate
Itching for a Cure
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