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SOURCE

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Source: Law RM, Gulliver WP. Psoriasis. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146069987. Accessed March 28, 2017.

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DEFINITION

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  • Chronic inflammatory skin disease characterized by recurrent exacerbations and remissions of thickened, erythematous, and scaling plaques.

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ETIOLOGY

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  • T lymphocyte-mediated inflammatory disease resulting from genetic predisposition coupled with precipitating factors that trigger abnormal immune response.

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PATHOPHYSIOLOGY

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  • Receptors on T lymphocytes interact with antigens on surface of antigen-presenting dendritic cells and macrophages.

  • Activated T cells migrate into skin and secrete cytokines (eg, interferon-γ and interleukin 2 [IL-2]) that induce pathologic skin changes.

  • Genetic component may involve human leukocyte antigens (HLA) Cw6, TNF-α, and IL-3.

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EPIDEMIOLOGY

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  • Affects about 2% of population in the United States and Europe.

  • Worldwide prevalence varies between 0.1% and 3%, with variations due to racial, geographic, and environmental differences.

  • Affects males and females equally; onset usually before age of 40.

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RISK FACTORS

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  • Factors implicated in development of psoriasis:

    • Skin injury.

    • Infection.

    • Drugs.

    • Smoking.

    • Alcohol consumption.

    • Obesity.

    • Psychogenic stress.

  • Therapies that may exacerbate psoriasis:

    • Lithium.

    • β-blockers.

    • Antimalarials.

    • Nonsteroidal anti-inflammatory drugs (NSAIDs)

    • Withdrawal of corticosteroids.

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CLINICAL PRESENTATION

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SIGNS AND SYMPTOMS
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  • Well-demarcated, erythematous, red-violet skin lesions at least 0.5 cm in diameter; typically covered with silver flaking scales.

  • May be single lesions at predisposed areas (eg, knees and elbows) or generalized over wide body surface area (BSA).

  • Pruritus may be severe and require treatment to minimize excoriations from frequent scratching.

  • Psoriatic arthritis involves both psoriatic lesions and inflammatory, arthritis-like symptoms.

    • Distal interphalangeal joints and adjacent nails most commonly involved, but knees, elbows, wrists, and ankles may also be affected.

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DIAGNOSIS

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MEANS OF CONFIRMATION AND DIAGNOSIS
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  • Characteristic skin lesions on physical examination.

  • Classification as mild, moderate, or severe based on BSA affected and Psoriasis Area and Severity Index (PASI) measurements.

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DIAGNOSTIC PROCEDURES
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  • Skin biopsies not diagnostic of psoriasis.

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DIFFERENTIAL DIAGNOSIS

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DESIRED OUTCOMES

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  • Minimize or eliminate skin lesions.

  • Alleviate pruritus.

  • Reduce frequency of flare-ups.

  • Avoid adverse treatment effects.

  • Provide appropriate counseling (eg, stress reduction).

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TREATMENT: GENERAL APPROACH

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  • Figure 1: Treatment algorithm for mild to moderate psoriasis.

  • Figure 2: Treatment algorithm for moderate to severe psoriasis.

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FIGURE 1.

Treatment algorithm for mild to moderate psoriasis. Reprinted with permission from Wells BG, DiPiro JT, Schwinghammer TL, et ...

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