TOC and Sample Chapters - McGraw-Hill Professional

S e c t i o n 3
Psoriasis and Psoriasiform
Dermatoses
Psoriasis
■ Psoriasis affects 1.5–2% of the population in
Western countries. Worldwide occurrence.
■ A chronic disorder with polygenic predisposition
and triggering environmental factors such as
bacterial infection, trauma, or drugs.
■ Several clinical expressions. Typical lesions are
chronic, recurring, scaly papules, and plaques.
Pustular eruptions and erythroderma occur.
Classification
Psoriasis vulgaris
Acute guttate
Chronic stable plaque
Palmoplantar
Inverse
■ Clinical presentation varies among individuals,
from those with only a few localized plaques to
those with generalized skin involvement.
■ Psoriatic erythroderma in psoriasis involving the
entire skin.
■ Psoriatic arthritis occurs in 10–25% of the
patients.
Psoriatic erythroderma
Pustular psoriasis
Pustular psoriasis of von Zumbusch
Palmoplantar pustulosis
Acrodermatitis continua
Psoriasis Vulgaris ICD-9: 696.1 ° ICD-10: L40.0 ◐
Epidemiology
Age of Onset. All ages. Early: Peak incidence occurs
at 22.5 years of age (in children, the mean
age of onset is 8 years). Late: Presents about age
55. Early onset predicts a more severe and longlasting
disease, and there is usually a positive
family history of psoriasis.
Incidence. About 1.5–2% of the population in
Western countries. In the United States, there
are 3–5 million persons with psoriasis. Most
have localized psoriasis, but in approximately
300,000 persons psoriasis is generalized.
Sex. Equal incidence in males and females.
Race. Low incidence in West Africans, Japanese,
and Inuits; very low incidence or absence
in North and South American Indians.
Heredity. Polygenic trait. When one parent
has psoriasis, 8% of offspring develop psoriasis;
when both parents have psoriasis,
41% of children develop psoriasis. HLA types
most frequently associated with psoriasis are
HLA- B13, -B37, -B57, and, most importantly,
HLA-Cw6, which is a candidate for functional
involvement. PSORS1 is the only consistently
confirmed susceptibility locus.
Trigger Factors. Physical trauma (rubbing and
scratching) is a major factor in eliciting lesions.
Acute streptococcal infection precipitates guttate
psoriasis. Stress is a factor in flares of psoriasis
and is said to be as high as 40% in adults
and higher in children. Drugs: Systemic glucocorticoids,
oral lithium, antimalarial drugs, interferon,
and β-adrenergic blockers can cause
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