Psoriasis is a common chronic inflammatory
skin disorder characterized by recurrent
exacerbations and remissions of thickened,
erythematous, and scaling plaques.
Psoriasis, a chronic proliferative skin disease
is one of the most common immune mediated
disorders occuring in 1.5- 3% of population
Of patients, 75% present with symptoms of
psoriasis before age 45yrs
Although rarely life-threatening, psoriasis has
an adverse physical and emotional impact on
quality of life.
Psoriasis is a complex and multifactorial
disease that is apparently associated with
interaction between environmental factors
(exogenous or endogenous antigens) and a
specific genetic background.
Factors such as
climate, stress, alcohol, smoking, infection, trauma, an
d drugs can aggravate psoriasis
Alcohol seems to have a greater influence on the
progression of psoriasis in men, and the association
between smoking and psoriasis seems to be stronger
Psoriatic lesions can develop at the site of injury on
normal appearing skin. This response can be induced
by a variety of trauma that includes
rubbing, venipuncture, bites, surgery, and mechanical
Lithium carbonate, β-adrenergic blocking
agents, some antimalarial agents, NSAIDS, and
There is a significant genetic component in
psoriasis, but the exact mode of inheritance is
Monozygotic twins have a higher concordance
for psoriasis than dizygotic twins.
The three key steps involved in the pathogenesis of psoriasis
i. T-cell activation by antigen in the lymph nodes
ii. T-cell binding to the endothelium in the vasculature, with
subsequent migration into the dermis and epidermis
iii. T-cell reactivation by a second exposure to antigen, which
occurs in the dermis. Certain CD4+ and CD8+ T cells have
a marker on their cell surface known as cutaneous
lymphocyte antigen (CLA)
• These CLA-positive T cells are recruited from the
circulation and migrate to the skin during inflammatory
processes and have been implicated in the pathogenesis of
various skin diseases, including psoriasis
• For these T cells to become activated, an APC(antigen
presenting cell) presents antigen to the T-cell receptor.
Clinical Presentation and
Most patients with psoriasis have symptoms of the
disease throughout their lifetime.
Patients who experience frequent
relapses, occurring within months or even
weeks, tend to develop more severe disease. The
palm of one's hand, from the wrist to the
fingertips, represents approximately 1% of the
body surface area (BSA). Disease affecting less
than 2% of the BSA is considered mild, moderate
psoriasis involves 3% to 10%, and severe
psoriasis involves more than 10% of the BSA.
Psoriasis Vulgaris or Plaque
Psoriasis vulgaris or plaque psoriasis, the most
common form of the disease, affects
approximately 80% of psoriasis patients.
Lesions are usually distributed in a symmetrical
pattern, typically located on the scalp, the lumbar
region of the back, and the extensor surfaces of
the elbows and knees. The well-demarcated
erythematous plaques covered with silvery scales
range in diameter from less than 1 cm to 10 cm.
The lesions are associated with pain and pruritus
and can occasionally crack and bleed. Scale
removal may result in punctate bleeding, also
called the Auspitz sign.
Guttate psoriasis commonly affects children
and young adults and is often associated with
recent streptococcal infections. The lesions
are usually small, scaly, and teardrop-shaped
and typically are localized to the
trunk, limbs, and scalp.
Inverse psoriasis is a form of psoriasis that
often exclusively involves the body folds.
Lesions usually present in the axillae, groin,
inframammary folds, navel, intergluteal crease,
and glans penis areas. Inverse psoriasis
presents as a large, smooth, dry, and very
erythematous lesion. This type of psoriasis is
more common in obese patients.
Pustular psoriasis is distinguished by the
development of white pustules encircled by
red skin. The pustules contain noninfectious
pus and are usually localized to the palms and
soles. Generalized disease affecting the entire
body often requires hospitalization and can be
Erythrodermic psoriasis is an acute
inflammatory, erythematous, scaling disorder involving the entire
Severe erythrodermic psoriasis and generalized pustular psoriasis
are associated with the loss of the protective functions of the skin.
These conditions are life-threatening because of the potential for
systemic infections, loss of thermoregulation, and cardiovascular or
Psoriatic arthritis is a chronic, progressive, inflammatory
arthritis that affects as many as about 30% of patients
with psoriasis.207,217 The arthritic symptoms are often
associated with the development of skin lesions and
include pain, swelling, and stiffness in the joints.
Furthermore, approximately 5% to 10% of those patients
may experience functional dis- ability.
Physical and psychological disability produced by the disease may
range from minor to total. Severe psoriasis is associated with
substantial morbidity and can cause functional impairment, skin
disfigurement, and emotional distress.
Approximately 30% of patients with psoriasis have moderate to
severe disease. The prevalence of depression and suicidal ideation
among patients with psoriasis is consistent with figures seen in
other populations with chronic illness.
Psoriasis directly affects the quality of life and may cause difficulty
in work performance, problems with social rejection, sexual
dysfunction, and depression.
Emollients are frequently used during therapy-
free periods to minimize skin dryness that can
lead to early recurrence.
As lotions, creams, or ointments, emollients
often need to be applied several times per day
(about four times per day) to achieve a
beneficial response. Adverse effects of
emollients include folliculitis and allergic or
irritant contact dermatitis.
Balneotherapy (and climatotherapy) is a
therapeutic approach that consists of bathing
in waters containing certain salts, often
combined with natural exposure to the sun.
Ultraviolet – B (UVB):
UVB light( sunburn spectrum, 290-320nm)
induces pyramidine dimers, inhibits DNA
synthesis and depletes intra epidermal T cells,
found in psoriatic epidermis
Heat and humidity from sunlight provide
additional positive effects
UVB treatments are administered 3 times
Risks: sunburn, photoaging, and skin cancer
Photochemotherapy combines psoralens with UVA light in the
320 to 400 nm spectrum.
Psoralens: methoxsalen, 8-methoxypsoralen, and trioxsalen.
Psoralens are a group of photoactive compounds that on
absorption of UV light, are both antiproliferative and
Photochemotherapy is used to control
severe, recalcitrant, disabling plaque psoriasis. After 10 to 20
treatments over 4 to 8 weeks, >80% of patients experience
clearing of symptoms, which can be maintained with periodic
(twice monthly) treatments.
8-Methoxypsoralen (8-MOP) is the most widely used
agent, taken at an oral dosage of 0.6 to 0.8 mg/kg of body
weight rounded to the nearest 10 mg, 1.25 to 1.5 hours
before exposure to UVA light.
Erythema, blistering, nausea, lethargy, headache, pruritus
Scabies is a contagious pruritic skin infection caused by
the mite Sarcoptes scabiei var hominis
Scabies is classified by the World Health
Organization as a water-related disease.
The disease may be transmitted from objects but is most
often transmitted by direct skin-to-skin contact, with a
higher risk with prolonged contact.
Scabies is 1 of the 6 major epidermal parasitic skin
diseases (EPSD) that is prevalent in resource-poor
populations, as reported in the Bulletin of the World
Health Organization in February 2009.
Prevalence rates are extremely high in aboriginal
tribes in Australia, Africa, South America, and other
developing regions of the world.
Incidence in parts of Central America and South
America and in one Indian village approach 100%.
In 2009 retrospective study of 30,078 children in
India, scabies was found to be the second most
common skin disease in all age groups of
children, and the third most common skin disease in
Pimple-like irritations or a rash
Intense itching, especially at night
Sores caused by scratching
The elderly and people with an impaired immune
system, such as HIV, cancer, or those
on immunosuppressive medications, are susceptible to
crusted scabies (formerly called Norwegian scabies).On
those with a weaker immune system, the host becomes
a more fertile breeding ground for the mites, which
spread over the host's body, except the face. Sufferers
of crusted scabies exhibit scaly rashes, slight
itching, and thick crusts of skin that contain thousands of
mites. Such areas make eradication of mites particularly
difficult, as the crusts protect the mites from topical
miticides, necessitating prolonged treatment of these
The entire lifecycle of mites usually lasts 30days
within the human epidermis.
After copulation, the male mite dies and female
mite burrows into the superficial skin and lays a
total of 60-90 eggs. The ova require 10 days to
progress through larval and nymph stages to
become mature mites.
Mites move through the top layers of the skin by
secreting proteases that degrade stratum
They feed on dissolved tissue but donot injest
Scybala (feces) are left behind as they travel
through the epidermis, creating linear lessions
In immunocompromised patients the weak
immune response fails to control the disease
and results in a fluminant hyper infestation
termed crusted scabies
Upon initial infestation, a delayed type-IV
hypersensitivity reaction to mites, eggs, or
scybala develops over 4-6 weeks.
Previously sensitized individuals can develop
symptoms within hours of re exposure.
The hypersensitivity reaction is responsible for
the intense pruritus.
Sulphur is the oldest antiscabietic in use. Celsus used
sulphur mixed with liquid pitch for management of
scabies as early as 25 AD.
Sulphur is used as an ointment (2%–10%) and
usually 6% ointment is preferred.
The technique is very simple: after a preliminary bath,
the sulphur ointment is applied and thoroughly rubbed
into the skin over the whole body for two or three
ADR: Topical sulphur ointment is messy,
malodourous, stains clothing, and in a hot and humid
climate may lead to irritant dermatitis
It is used as a 25% emulsion and the contact
period is 24 hours.
Benzyl benzoate should be applied below the
neck three times within 24 hours without an
In young adults or children, the dosage can be
reduced to 12.5%.
ADR: Repeated usage may lead to allergic
CI: in pregnant women, lactating women, children
less than 2 yrs.
Crotamiton (crotonyl-N-ethyl-o-toluidine) is used
as 10% cream or lotion.
The best results have been obtained when
applied twice daily for five consecutive days after
bathing and changing clothes.
Malathion is an organophosphate insecticide that
irreversibly blocks the enzyme
Malathion is not recommended nowadays for
treatment of human ectoparasitic infestations
because of the potential for severe adverse
Monosulfiram emulsion is applied all over the
body after a bath, and it should be rubbed in
well once a day on two or three consecutive
Monosulfiram is chemically related to
antabuse and hence alcoholic beverages
should be avoided during or soon after
Soaps containing monosulfiram have been
used in the past as a prophylactic measure in
It acts on the central nervous system (CNS) of insects and leads to
increased excitability, convulsions, and death.
A single six hour application is effective in treatment of scabies.
Some authors recommend a repeat application after one week.
Lindane 1% cream or lotion has been found to be very effective in
the treatment. It is non-irritating and ease of application has made it
a popular treatment.
ADR: it can cause CNS toxicity and rare cases of CNS
toxicity, convulsions, and death
Accidental ingestion can lead to lindane poisoning.
The clinical signs of CNS toxicity after lindane poisoning include
headache, nausea, dizziness, vomiting, restlessness, tremors, disor
ientation, weakness, twitching of eyelids, convulsions, respiratory
failure, coma, and death.
Permethrin is a synthetic pyrethoid and potent
insecticide.4 Permethrin is very effective
against mites with a low mammalian toxicity.
Permethrin 5% dermal creams are applied
overnight once a week for two weeks to the
entire body, including the head in infants. The
contact period is about eight hours.
Oral antiscabietic agent
Ivermectin, the 22, 23 dihydro derivative of avermectin B1 is
similar to macrolides, but without any antimicrobial action.
MOA: It acts via the suppression of conduction of nerve
impulses in the nerve-muscle synapses of insects by
stimulation of gamma amino butyric acid from presynaptic
nerve endings and enhancement of binding to postsynaptic
DOSE: Scabies is treated with ivermectin 0.2 mg/kg in a
ADR:headache, pruritus, pains in the joints and
muscles, fever, maculopapular rash, and lymphadenopathy
CI: patients with an allergy to ivermectin and CNS disorders.
It is also not indicated during pregnancy, lactation, and in
children less than 5 years of age.
Allethrin I, widely used as an insect
repellent, was effective when used as a spray
Thiabendazole 5% cream has been tried in
treatment of resistant scabies.