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

There's more to see -- the rest of this topic is available only to subscribers.