What is Psoriasis?
Psoriasis is a common disorder affecting between 1% and 2% of the population
that can appear at any age and runs a very unpredictable course. In
most patients, the disorder is confined to the skin where it develops
as small to large, thickened plaques covered with a fine silvery scale.
Plaques of psoriasis result from an abnormality of the epidermis which
is the most superficial layer on the surface of the skin. In psoriasis,
the cells of the epidermis multiply at an abnormally rapid rate so
in effect, too much skin is being produced and it becomes thickened
and scaly. It is now known that an abnormal immune response causes
the skin to react in this way and psoriasis is now considered to be
an auto-immune disease. White blood cells enter the skin and release
chemicals to cause the skin cells to multiply.
Genetic Factors - About 70% of patients with psoriasis have a near
or distant relative with the disorder. However, the inheritance is
somewhat indirect and a child of a patient with psoriasis has only
about a 10% risk of developing the disorder at any time in his or her
Infections - A viral or bacterial infection of the throat can trigger
psoriasis but such infections do not tend to make established psoriasis
Psychological Factors - Psoriasis may appear for the first time during
a period of stress but more importantly, emotional stress frequently
exacerbates psoriasis in a person who already has the disorder.
Trauma - Abrasion of the skin and blunt trauma can provoke new areas
of psoriasis in a person with the disorder. Scratching of the skin
has a similar effect. Localization of psoriasis to the knees and elbows
is probably due to the repeated knocks received by these parts of our
Pregnancy - Psoriasis frequently goes into remission during pregnancy
but also, it often appears for the first time after delivery.
Finally, we can say that several factors are not important in causing
psoriasis. Psoriasis is not an infectious disease and it is not caused
by any known bacteria or virus. Diet has no proven influence on psoriasis.
Psoriasis is not caused by a vitamin deficiency and is not improved
by taking ordinary vitamins.
Psoriasis and Arthritis
Approximately 12% of patients with psoriasis have a form of arthritis
that is peculiar to this disease and differs from other types of arthritis.
The arthritis can precede, accompany or follow appearance of the skin
rash, and it predominantly affects the small joints of the fingers
and the pelvic joints. Most patients are only mildly affected.
It must be remembered that other types of arthritis, in particular
rheumatoid arthritis, do afflict patients with psoriasis just the same
as they afflict patients who do not have psoriasis. Therefore, the
appearance of arthritis in a person with psoriasis does not necessarily
indicate the two disorders are related.
Treatment of Psoriasis
There are many treatments for psoriasis and that is always a certain
indication that no one treatment is perfect. All treatments aim to
block the rapid multiplication of cells in the epidermis. The amount
of treatment, the intensity of treatment, and the type of treatment
must be tailored to the individual patient. The most common employed
Various lotions, creams and ointments are used to control mild-to-moderate
cases of psoriasis. The advantage of this approach is its convenience
since it can be done at home and usually does not involve too much
time and effort. The disadvantage of topical therapy is that although
it usually produces improvement of psoriasis it does not clear the
condition. The most common forms of topical therapy are:
Lotions, shampoos and creams containing tar have been used for many
years. Tar is mildly effective in slowing down the multiplication of
cells and is safe to use even if a little messy.
Hydrocortisone and more potent derivatives, as creams and lotions are
effective in improving psoriasis. These preparations are safe and useful
in patients with only small areas involved but unfortunately, when
used on large areas they are less effective and prone to give rise
to adverse effects.
The principal harmful effects are precipitation of extensive psoriasis
once they are stopped, atrophy or thinning of the skin (stretch marks)
and suppression of the normal function of the adrenal glands; the latter
problem can result in shock and collapse if the patient contracts a
severe infection or suffers a severe injury.
Cortisone has also been given as injections and tablets in the treatment
of psoriasis. Although this treatment is initially very effective,
psoriasis soon becomes resistant and adverse effects are very common.
Vitamin D Derivatives
Calcipotriene or Dovonex cream and ointment are more recent additions
to the choice of topical treatments. When used twice daily in a sustained
manner they produce considerable improvement in many patients. The
main problem with treatment is irritation of the skin that occurs in
some patients. If used in excessive amounts there is concern about
interfering with calcium balance in the body.
Tazarotene or Tazorac, a gel formulation, is another new addition to
topical therapy. This compound is a retinoid or vitamin A derivative
and it is moderately effective in treating psoriasis. The main drawback
of the treatment is irritation of the skin that occurs in many patients.
This problem can be partly relieved by combining its use with corticosteroid
Ultraviolet Light Treatment
Most people with psoriasis notice they are better in summer than winter
and this is mainly due to the beneficial effect of sunlight. The ultraviolet
portion of sunlight is responsible for this improvement.
The main advantage of ultraviolet or UV treatment is that it converts
psoriasis to skin that looks and feels normal and with maintenance
treatment, it can be maintained in a normal state. UV treatment, to
be effective, usually has to be done in a doctor’s office and
therefore it is mainly reserved for patients with moderate to extensive
The main downside of UV treatment is that it does cause premature aging
of the skin and skin cancer but if used carefully in modest amounts
it is the safest and most effective treatment for psoriasis.
Several types of UV treatment are available:
High-intensity Broadband UVB Phototherapy
• Clears many patients in about 30 treatments and can be used as maintenance
treatment once or twice a week.
Narrow-band UVB Phototherapy
• A newer treatment that is more effective and can clear about 80% of
selected patients with psoriasis.
• The most effective form of UV therapy clearing over 90% of all patients
with psoriasis and maintenance treatment is usually about twice a month.
• The excimer laser which emits ultraviolot light has recently been approved
for treating localized small areas of psoriasis.
Various medications taken by mouth or injection can be very effective
in clearing psoriasis. These are usually reserved for people with moderate-to-severe
disease unresponsive to other treatment because they are all associated
with significant side effects.
This is an agent that has been used in the treatment of cancer for
several decades and in much smaller doses, it is also effective in
the treatment of psoriasis. When used in short courses, as for example
in combination with a course of ultraviolet light, methotrexate is
a safe and very effective agent and requires only minimum supervision.
However, chronic use over long periods can interfere with the function
of the liver and close monitoring is required to check for this adverse
Acitretin or Soriatane
A new compound that is a derivative of vitamin A has some effect in
psoriasis. However, this beneficial effect is mainly confined to people
with pustular and erythrodermic psoriasis, and both of these very severe
forms of the disorder are fortunately quite rare. The use of retinoids
will probably be limited because they produce adverse effects in all
patients including changes in the bones and in the lipids in blood.
Cyclosporine or Neoral
Also new for the treatment of psoriasis, this is an agent that suppresses
the immune system and can be very effective in treating psoriasis.
It is usually used for short courses in patients with severe psoriasis
since long-term use can affect the function of the kidneys.
Recently, a number of antibody agents which block the inflammation
causing psoriasis, have been approved for tratment. these are given
by injection into the skin or into veins and can be very effective
in treating the disease either alone or in combination with light and
The Course of Psoriasis
Psoriasis is a chronic and unpredictable disorder that may last months
or years. There are four important facts to remember:
• Psoriasis does undergo spontaneous remission so that 10% of all people
who have psoriasis this year will not have it next year.
• There is no marker or indicator that will tell us then a particular
patient is likely to undergo a remission.
• All available treatments are just that, treatment and not cures. None
of these treatments influence the natural course of the disorder.
• New treatments appear at the rate of one or two each year. Effective
treatments appear at a rate of one each decade.
While these facts might at first glance be somewhat discouraging, psoriasis
is a treatable condition and should not restrict a fairly normal life
provided the therapeutic modalities we have today are correctly used
in the individual management of each patient.