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Psoriasis is a
noncontagious inflammatory skin
condition. It is often defined
as a common chronic, or recurrent disease.
Psoriasis is characterized by dry, well
circumscribed, silvery scaling
papules and plaques of various
sizes. [1] Approximately 3 million
Americans are affected (8 out of
every 10,000 people). Psoriasis
generally appears between the ages
of 15 to 35 years old. Caucasians
are at the greatest risk, as whites
are diagnosed more frequently than African-Americans. Men and women are
equally affected. There is also a
strong genetic predisposition for the
disease. |
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Although the actual
cause
of psoriasis is unknown, the pathophysiology is well documented.
Normally, skin cells turn over in
about a month. Cells from
the lowest layer of skin move to the
surface, primarily the keratinocytes. However, in persons with psoriasis
this process takes only three or
four days. The keratinocyte's cell
cycle is altered, thereby changing the
balance and homeostasis of certain cell signals,
specifically cAMP (cyclic adenosine
monophosphate) and cGMP (cyclic
guanidine monophosphate).
Psoriasis causes cGMP signals to elevate and cAMP
to decrease. This leads to a
defining characteristic is psoriasis
patients-increased cell numbers. [2] Clinically, inflammation of the
dermis and a build up of dead skin
cells which form thick scales, is
also observed.
Proposed causes of
psoriasis include elevated cGMP
due to oxidative stress. Oxidative
stress can be the result of alcohol
consumption, food allergies, stress, and infection.
Incomplete
protein digestion, bowel toxemia, and
liver function have been linked to
psoriasis as well. These
possible causes are, more than
likely, linked to the abovementioned
connection of oxidative stress and
altered cGMP/cAMP levels. [3]
The onset of
psoriasis can be gradual or
sudden, but usually appears after a
number of months. Patients complain
of itchy skin patches that may be
dry and red, and then become covered
with silver scales. Affected patches
of skin are raised and have a red
border. The scales can crack and
bleed. Commonly affected boy locations include; extensor
surface of elbows and knees, the
trunk, scalp, buttocks, sacral area,
hands, and occasionally nails (which
may be psoriatic arthritis if the
patient also suffers from arthritic
symptoms). [1]
The course of
psoriasis is generally characterized
by chronic remissions, recurrences
and/or possibly
exacerbations. Almost 50% of
patients report that a stressful
event occurred within one month of
the first episode. [4] Once the first episode has occurred,
some factors may then precipitate
future flare-ups, such as; severe
sunburn, viremia, group A
β-hemolytic streptococcal upper
respiratory infection, allergic drug
reactions, and topical and systemic
drugs such as β–blockers and
lithium.
Other conditions that
may mimic psoriasis include; atopic
dermatitis, lichen simplex chronicus,
seborrheic dermatitis, secondary or
tertiary syphilis, Reiter's
syndrome, candidiasis, lichen planus,
pityriasis rosea and tinea corporis.
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Learn More About
Psoriasis |
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