Psoriasis

Basics

Description

  • Chronic, noncontagious, inflammatory skin condition
  • Complex immune mediated disease of hyperproliferation
  • Presents with well-demarcated, erythematous plaques with silver scaling
  • Most commonly affects the elbows, knees, lumbar area, gluteal cleft, and glans penis
  • Associated with multiple comorbidities
  • Up to 30% of patients develop psoriatic arthritis and 10% have ocular manifestations
  • Course is unpredictable; marked variability in severity over time and remissions/relapses may be seen
  • Exact cause unclear; triggers may include infectious, stressors, medications, or trauma
  • Tends to show improvement in summer months, possibly related to UV exposure
  • Prevalence tends to increase with increasing distance from equator
  • Associated with metabolic syndrome
  • Caucasians and atopics most affected
  • Prevalence in adults range from 1–8% and 0–2% in children
  • Generally affects males and females equally
  • 2 peaks of onset: Between ages 30–39 and 50–69
  • Rare cause of mortality, but at least 100 deaths annually in the U.S. related to severe disease and/or treatment adverse effects
  • Several clinical presentations:
    • Chronic plaque psoriasis (psoriasis vulgaris):
      • Most common form (75–80%) with erythematous, raised plaques with well-demarcated borders distributed over the scalp, back, and extensor side of the knees and elbows
    • Guttate psoriasis:
      • Abrupt appearance of multiple, discrete, salmon-colored, “drop-like” papules with a fine scale in a patient with no prior history of psoriasis
      • Most commonly seen on the trunk and proximal extremities
      • Often preceded by a streptococcal infection and resolves spontaneously
    • Pustular psoriasis:
      • Occasionally isolated to the palms and soles, but can present as widespread erythema, scaling, and sheets of superficial pustules with erosions
      • Patient may appear toxic and have other systemic symptoms, like malaise, fever, and diarrhea
      • Potentially severe and life threatening and treated as an inpatient if generalized
    • Erythrodermic psoriasis:
      • Generalized erythema and pruritus with a fine scale
      • Increased risk for infection, dehydration
      • Often treated as inpatients
    • Inverse flexural psoriasis:
      • A variant that causes lesions in flexural areas and in skin folds that do not exhibit scaling due to moisture in these areas
    • Nail psoriasis:
      • Pitting over the nail plate or change in nail bed
      • Nail changes in up to 50% of patients
    • HIV-induced psoriasis:
      • May be the first manifestation of AIDS, more frequent and severe in HIV population
  • Genetics:
    • Genetic factors play vital role in determining susceptibility
    • Psoriasis-susceptibility (PSORS1) locus within the major histocompatibility complex (MHC) on chromosome 6p21 is considered a major genetic determinant of this disease
    • 40% of patients with psoriasis have a family history in a first-degree relative

Etiology

  • Typical findings of erythema and scaling are the result of increased number of epidermal stem cells and keratinocyte hyperproliferation, shortened cell cycles, inflammatory infiltrates, and vascular changes
  • Triggers include:
    • Drugs:
      • Lithium
      • β-Blockers
      • Antimalarials
      • Steroid withdrawal
      • NSAIDs
      • Alcohol
      • Significant risk factor for mortality in psoriasis patients
      • Potassium iodide
    • Infections:
      • Streptococcal pharyngitis
      • HIV
      • Staph
    • Local trauma:
      • Frostbite
      • Sunburn
      • Recent skin trauma (Koebner phenomenon)
    • Stress: Emotional and physical
    • Winter:
      • Low light exposure
      • Dry weather
    • Cigarette smoking
    • Elevated BMI

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