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  icon Rare
  icon Not so common
  icon Common
  icon Low morbidity
  icon Considerable morbidity
  icon Serious

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.

  • 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.

Classification

  • Psoriasis vulgaris

    • Acute guttate

    • Chronic stable plaque

    • Palmoplantar

    • Inverse

  • Psoriatic erythroderma

  • Pustular psoriasis

    • Pustular psoriasis of von Zumbusch

    • Palmoplantar pustulosis

    • Acrodermatitis continua

Psoriasis Vulgaris

ICD-9: 696.1 ○ ICD-10: L40.0 Image not available.

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 long-lasting 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 flares and cause a psoriasiform drug eruption. Alcohol ingestion is a putative trigger factor.

Pathogenesis

The most obvious abnormalities in psoriasis are (1) an alteration of the cell kinetics of keratinocytes with a shortening of the cell cycle resulting in 28 times the normal production of epidermal cells and (2) CD8+ T cells, which are the overwhelming T cell population in lesions. The epidermis and dermis react as an integrated system: the described changes in the germinative layer of the epidermis and inflammatory changes in the dermis, which trigger the epidermal changes. Psoriasis is ...

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