Psoriasis

BASICS

DESCRIPTION

  • A chronic, inflammatory disorder commonly characterized by cutaneous erythematous plaques with silvery scale, and varying phenotypes and severity
  • Clinical phenotypes:
    • Plaque (vulgaris): ~80% of cases; well-demarcated, red plaques with silvery scale on the scalp, extensor surfaces, and trunk
    • Guttate: <2% of psoriasis patients, usually in patients <30 years of age; abrupt onset of 1-mm to 10-mm droplet-shaped papules with fine scale on the trunk and extremities; often following a group A β-hemolytic streptococcal infection 2 to 3 weeks prior; typically, self-limiting and may resolve spontaneously.
    • Inverse: affects intertriginous areas and flexural surfaces; pink-to-red plaques with minimal scale; lacks satellite pustules, a key feature distinguishing it from candidiasis
    • Erythrodermic: affects 90% or more of body surface area (BSA) with generalized erythema and scaling; associated with desquamation; hair loss; nail dystrophy; and systemic symptoms (chills, malaise, lymphadenopathy, and/or high-output cardiac failure)
    • Pustular: Sterile pustules can present in localized or generalized forms. Generalized pustular psoriasis may lead to severe systemic illness, including superinfection.
    • Nail disease: pitting, oil spots, and onycholysis; nails involved in 50% with psoriasis at diagnosis with lifetime incidence of 80–90% with cutaneous psoriasis; increased association with psoriatic arthritis

EPIDEMIOLOGY

Incidence

Predominant age: two peaks of incidence between the ages of 20 to 30 years and 50 to 60 years

Prevalence

  • 3.2% prevalence in the United States
  • In the United States, the most commonly affected demographic group is non-Hispanic Caucasian.

ETIOLOGY AND PATHOPHYSIOLOGY

Psoriasis involves immune dysregulation of dendritic cells, T lymphocytes, and keratinocytes, triggered by infections, stress, and trauma.

Genetics

  • Genetic predisposition (polygenic)
  • 40% have psoriasis in a first-degree relative.
  • Multiple susceptibility loci contain genes involved in immune system regulation.
  • HLA-C*06 is most strongly correlated with early onset psoriasis.

RISK FACTORS

  • Family history
  • Obesity
  • Local trauma; local irritation (Koebner phenomenon)
  • HIV
  • Streptococcal infection
  • Stress (may contribute to exacerbation)
  • Medications: lithium, antimalarials, β-blockers, interferon, TNF-α inhibitors, steroid withdrawal
  • Smoking
  • Alcohol abuse
  • Dysbiosis of gut microbiota

GENERAL PREVENTION

Avoid triggers like trauma, sunburn, smoking, certain medications, alcohol, and stress.

COMMONLY ASSOCIATED CONDITIONS

  • Psoriatic arthritis
  • Seborrheic dermatitis
  • Obesity, metabolic syndrome, diabetes, chronic kidney disease
  • Cardiovascular disease, atherosclerotic disease
  • Nonalcoholic fatty liver disease (NAFLD)
  • Other autoimmune conditions: Crohn disease, ulcerative colitis, ankylosing spondylitis
  • Psychiatric/psychological conditions: depression, anxiety, suicidal ideation, low self-esteem, alcohol abuse, sexual dysfunction
  • Myopathy

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