Despite being the subject of
intensive research over the years, the precise aetiology of psoriasis
still remains unknown.
Genetic factors can be implicated on the
basis of population surveys, twin studies and analysis of pedigrees. But
the precise mode of inheritance is uncertain, thought to be polygenic. HLA
system provides a potential genetic marker. Different groups of psoriatics
population showed the following to be significantly associated with
psoriasis.: HLA Cw6, B13, B16, and B27.
factors : A number of factors may provoke onset or
aggravation of psoriasis.
- Trauma - All types of trauma can
lead to the development of plaque psoriasis (eg, physical,
chemical, surgical, infective, and inflammatory). The
development of psoriatic lesions at a site of injury is known as the
- Infection – An acute eruption of
guttate psoriasis may be provoked by streptococcal pharyngitis.
HIV infection may be associated with increase in disease
- Drugs. Lithium ,withdrawal
of systemic corticosteroids, beta-blockers, antimalarials, and
NSAIDs may cause flare of the disease
- Sunlight – although sunlight
is generally considered to be beneficial for most of the
patients, strong sunlight may worsen the disease in a small minority
- Stress - Many patients report an
increase in the psoriasis severity with psychological stress.
- Smoking - Cigarette smoking is
associated with an increased risk of chronic plaque psoriasis
- Alcohol - Alcohol is considered a
risk factor for psoriasis, particularly in young to middle-aged
- Endocrine – the disease state may
fluctuate with hormonal changes. Psoriasis may begin during puberty.
Pregnancy may improve the disease. while a flare may occur during
Role of immune
Although the exact
immunopathogenesis of psoriasis is unknown, immunologic factors have been
implicated in its etiology . Psoriatic plaques are characterized by
epidermal hyperplasia, presence of acute and chronic inflammatory
cells vascular changes of inflammation . The epidermis and dermis of an
active psoriatic plaque contain increased numbers of several different
cells of the immune system, including activated T cells, activated
antigen-presenting cells (APCs) (Langerhans cells, other dendritic cells
and macrophages), neutrophils, and hyperproliferating keratinocytes . The
activation of APCs, keratinocytes or dermal cells may result in induction
of antigen presentation, cytokine release, and enhanced T-cell
activation and lymphokine release.. Lymphokines, in turn, produce
inflammation and hyperproliferation of epidermal cells. Accelerated
epidermal cell proliferation results from recruitment of a large
proportion of resting cells into the proliferative cycle.
Antigen presentation by
T lymphocyte- mediated
Clinical Lesions of
The pathology of
psoriasis reflects the underlying immune-mediated inflammation
and cellular hyperproliferation.
parakeratosis (presence of nucleated keratinocytes in the stratum
corneum due lack of maturation of cells since rapid transit time
do not permit normal maturation of cells).
Reduced or absent
elongation of rete ridges and a corresponding upward elongation of
Mononuclear in dermis and polymorphs in the upper epidermis
forming collections called ‘microabscess of Munro’.
vasculature shows dilatation and
Family history is
at any age but two peaks are observed: the first peak in the second
decade , the second in the sixth decade.
Onset may follow
trauma, infection, sunburn or psychological
Patients complain of
prominent itchy, elevated red areas with increased
recognize that new lesions appear at sites of injury to the
(This isomorphic phenomenon (Koebner reaction) typically occurs 7-14
days after the skin has been injured and has been found in 40-80% of
patients with psoriasis.
In some patients, so-called
reverse-Koebner reactions may be noted in which preexisting
psoriatic plaques will clear after injury or trauma to the
Koebner reaction may also be found in
other dermatoses like, lichen planus, lichen nitidus, verruca plana
and vitiligo )
stiffness, and deformity are complaints in about10% of patients who
have psoriatic arthritis.
patients may present in a variety of ways with overlapping features
being not uncommon.
psoriasis. The commonest
type, presenting with typical plaques of psoriasis of the extensors
psoriasis. Is commoner
in childhood. Acute eruption of drop-shaped lesions distributed
widely over the body. Usually follows an upper respiratory
psoriasis: lesions are
present over the flexors and intertriginous areas( axilla, groin,
umbilical region, inframammary folds) the lesions may be moist and
lack the typical scaling.
psoriasis. may be
localized or generalized. Localized pustular psoriasis
usually presents with persistent pustular eruptions of the hands and
Generalized pustular psoriasis may occur as an explosive
eruption of generalized pustules with systemic disturbances. This
may follow withdrawal of systemic steroid therapy or application of
psoriasis . Arthritis
may accompany any variety of psoriasis in about ten per cent of
patients . Psoriatic arthritis may take several forms. The
commonest type is asymmetrical oligoarthritis, other types
are: symmetrical seronegative rheumatoid-like disease ,
distal interphalangeal involvement( most characteristic, but
relatively rare), axial skeletal involvement, and a
destructive mutilating form (arthritis mutilans)
psoriasis. Psoriasis may
(exfoliative dermatitis) There is
generalized inflammatory erythema with profuse scaling.
The typical lesions of psoriasis have
the following features;
The lesions are very
well marginated with distinct
The lesions are
raised above the
The plaques usually
have a diameter of one to several centimeters and have a
round or oval
The lesions may merge together to give rise to geographic
typically have a rich red
and may be surrounded by a pale halo ( the halo of Woronoff).
The lesions are
covered with a silvery white, mica-like, loosely adherent
scales which, on removal
may reveal punctate bleeding points (Auspitz sign)
Symmetry:: the lesions are
symmetrically disposed on extensor surfaces of the body. Typical
sites of affection are the elbows, knees, shin, knuckles, sacral
areas and scalp.
Uniformity: the psoriatic
plaques tend to have the same features irrespective of site except
for certain locations like the palms and soles, and the flexors.
Variations by morphology or
from the typical plaque lesions, guttate lesions and pustules,
lesions may take on a variety of morphological forms and shapes.
Verrucous, lichenoid, follicular, linear, annular, figurate, gyrate
are some of the terms used to describe these variants.
Variations by site:
Scalp: Diffusely involved. Thick scaling, no
Penis:. Well-circumscribed reddish plaque
Hands and feet: Diffuse hyperkeratosis, Thick scales,
Sacral regions: thick fissures plaques, scaling may be
Nails: involved in 25 to 50% of cases.
Onycholysis (separation of nail-plate from the
nail bed) giving rise to oil-drop sign.
Thickened friable nail
and 2: showing typical plaques of
|Diagnosis of psoriasis
is usually straightforward and based on typical clinical features
alone. However, in certain cases, depending on the type and site of
lesions, the following diseases may need to be considered in the
Tinea corporis and cruris
eczema of hands and feet
|Since psoriasis is a
chronic disease, therapy is long-term. There are many treatment options
available. Treatment regimens must be individualized according to
age, sex, occupation, type and extent of disease and available
Three main modalities of therapy
are used: topical, phototherapy and systemic agents. These are used
either alone or in combinations.
THERAPY - Outpatient
topical therapy is the first-line approach in the treatment of
Topical steroid :Potent
topical steroids, applied twice a day is effective in controlling
limited plaque psoriasis. Intralesional injection of triamcinolone
acetonide into isolated chronic plaques may also be used/
Anthralin (Dithranol): Derived from chrysarobin (active
ingredient of Goa powder, derived from the bark of South American
Araroba tree), it has antiproliferative and immunosuppressive
action. It is best applied as short-contact therapy (washing off the
medicine after a contact period of 10 to 30 minutes). Dithranol is
irritant and can stain cloth , it causes a reversible brownish
pigmentation of the treated skin.
Vitamin D3 analogues: Calcitriol and Calcipotriol
are as effective as topical steroids and anthralin. Act by
regulating keratinocyte proliferation and maturation. Side effects
include irritation and hypercalcemia and kidney stones with high
Retinoids: The synthetic retinoid
Tazarotene when used topically, can regulate keratinocyte
proliferation and maturation. Main side effect is irritation.
Special precaution: women of child-bearing age.
Coal tar: Tars have
antiproliferative effect. May be combined with steoid therapy. Coal
tar solution may be used for scalp psoriasis.
Salicylic acid: As a two
to ten per cent ointment, often combined with topical steroids,
helps remove scales and also helps in penetration of steroids.
PHOTOTHERAPY - Phototherapy is used in the cases
of extensive, widespread disease resistant to topical
treatment Proper facilities are required for the two main forms of
- UVB - Ultraviolet B
utilizes ultraviolet radiation with wavelengths 290-320 nm
(visible light range is 400-700 nm). It is used alone or
combined with one or more topical treatments. The Goeckerman
regimen uses coal tar followed by UVB exposure and the
Ingram method is based on anthralin application following
a tar bath and UVB treatment. UVB more commonly is now combined
with topical corticosteroids, calcipotriene, tazarotene, or
simply bland emollients. UVB phototherapy is extremely effective
for treating moderate-to-severe plaque psoriasis. Narrow-band
UVB (UVB of 311 nm wave length) is now increasingly used for
its effectiveness and low potential for photodamage.
In this therapy (also known as PUVA), a
photosensitizing drug methoxsalen (8-methoxypsoralens) is given
orally, followed by ultraviolet A (UVA) irradiation to
treat patients with more extensive disease. UVA irradiation
utilizes light with wavelengths 320-400 nm. PUVA, decreases
cellular proliferation by interfering with DNA synthesis, and
also induces a localized immunosuppression by its action on T
lymphocytes... Therapy usually is given 2-3 times per week on an
outpatient basis, with maintenance treatments every 2-4 weeks
until remission. Adverse effects of PUVA therapy include nausea,
pruritus, and burning. Long-term complications include increased
risks of photo damage and skin cancer. PUVA has been combined
with oral retinoid derivatives to decrease the cumulative dose
of UVA radiation to the skin.
- Systemic treatments are
used when both topical treatments and phototherapy have
failed. Also used for patients with very active psoriatic
arthritis, erythrodermic psoriasis and generalized pustular
psoriasis. Patients who have disabling disease through physical,
psychological, social, or economic means also are considered
candidates for systemic treatment.
Methotrexate is the most popular agent used. A weekly oral
or intramuscular dose of 15 to 25 mg is used. Started with low
dose and gradually increased to the desired dosage. 5mg 12 hourly
X 3 doses per week is the usual oral regimen. CBC, platelets, LFT,
urinalysis, and creatinine. must be normal before starting
therapy. These tests are repeated at regular intervals to monitor
toxicity. Main side effects are nausea, vomiting, hepatic
dysfunction (even fibrosis on long term therapy), and microcytic
anemia. Hydroxyurea is the alternative antimetabolite. It
is more toxic than methotrexate and rarely used.
Acitretin: A synthetic vitamin A derivative. Is
used in a dose of 10 to 20 mg/day gradually increased to the
maximum dose of 50mg/day. Main side effects are : teratogenicity
(the drug should not be used in women of child-bearing potential)
, hypertriglyceridemia, xerosis of skin, chelitis and alopecia. It
may be used in combination with phototherapy, methotrexate or
Cyclosporine: this drug selectively inhibits
T-helper cell production of IL-2 and thus exerts an
immunosuppressive effects. The usual dosage is 3 to 6mg/kg per
day. A new microemulsion formulation may be used in a lower
dosage. The commonest side effects are hypertension and
mofetil: still under evaluation, this newly
introduced drug inhibits synthesis of the nucleotide guanosine.
The recommended dosage is500mg four times a day with a maximum
dose of 4 gm . side effects are: teratogenicity, neutropenia, GI
symptoms, and opportunistic infections.
Sulphasalazine may be used to treat psoriasis either
alone or combined with methotrexate, particularly in psoriatic
are relatively uncommon.
- Many of the
complications (pustular psoriasis, erythroderma) are commonly due
to inappropriate and aggressive therapy.
and its metabolic complications.
particularly Staph. infections of the patches.
- Eczematization due to topical
- Amyloidosis ,
rare sequel to arthropathic of pustular psoriasis.
consequences : depression, anxiety, lack of self-esteem.
complications of systemic therapy should not be overlooked.
- The course of
plaque psoriasis is unpredictable. The duration of active disease,
the time or the frequency of relapses, or the duration of a
remission are unpredictable.. The disease rarely is life
threatening, but often is intractable to treatment with relapses
occurring in the majority of patients.
- Both early
onset and family history of disease are considered poor prognostic
- Some suggest
that stress also is associated with an unfavorable