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Snapshot
  • A 15-year-old boy with a history of Crohn disease who is on infliximab presents with a new rash. He reports pain preceding a new pink rash with tiny white “dots” all over his back. He has been taking infliximab for 1 year now and without issue. On physical exam, there are dozens of 1 mm pustules overlying erythematous skin with no scaling. A bacterial swab of the pustules reveal only normal skin flora. He is diagnosed with pustular psoriasis induced by infliximab. He is immediately started on other systemic therapy for both his Crohn disease and pustular psoriasis.
Introduction
  • PhotoClinical definition
    • idiopathic and chronic inflammatory disease characterized by hyperkaratosis and parakeratosis
  • Classification
    • plaque psoriasis
      • most common
      • well-defined erythematous plaques with scales
      • typically over extensor surfaces
    • inverse/intertriginous psoriasis
      • plaques with minimal scaling in skin folds
    • pustular psoriasis
      • pustules rather than plaques
    • erythrodermic psoriasis
      • generalized erythema covering almost entire body surface area
      • a medical emergency
    • guttate psoriasis
      • 1- 10 mm pink macules with scaling
  • Epidemiology
    • incidence
      • US incidence
        • 2% of population
    • demographics
      • normally, > 40 years of age but can affect people of all ages
    • risk factors
      • smoking
      • skin trauma
      • alcohol abuse
      • stress
      • cold weather
  • Etiology
    • idiopathic
    • drugs
      • while tumor necrosis factor-alpha (TNF-α) inhibitors are a treatment for psoriasis, it can cause new-onset “paradoxical” psoriasis when used for another inflammatory disease (such as Crohn disease)
      • β-blockers may exacerbate psoriasis
  • Pathogenesis
    • hyperproliferation of basal stem keratinocytes
    • ↑ inflammation, especially inflammatory markers IL-6, C-reactive protein, TNF-α, E-selectin, and ICAM-1
  • Associated conditions
    • psoriatic arthritis
Presentation
  • Symptoms
    • painful or pruritic skin lesions
    • joints may be painful or stiff
      • especially in feet and hands
  • Physical exam
    • plaque psoriasis
      • well-circumscribed, pink papules and flat-topped plaques with silvery scales
      • common locations
        • scalp
        • trunk
        • buttocks
        • extensor surface of limbs
        • positive Auspitz sign
          • when scales are scraped off, there is pinpoint bleeding
            • results from exposure of dermal papillae
        • nail changes 
          • pitting
        • Koebner's phenomenon
          • psoriatic lesions appear at site of cutaneous physical trauma
    • pustular psoriasis
      • sterile pustules on erythematous skin
    • guttate psoriasis
      • salmon pink papules with fine overlying scales
      • location
        • trunk
        • proximal extremities
Studies
  • Labs
    • electrolytes
      • there may be electrolyte imbalances if psoriasis is erythrodermic
  • Histology
    • acanthosis with parakeratosis (thickened stratum corneum with preserved nuclei)
    • hyperkeratosis (thickened epidermis)
    • Munro microabscesses
    • ↑ stratum spinosum
    • ↓ stratum granulosum
  • Diagnostic criteria
    • diagnosis is primarily based on clinical exam and history
Differential
  • Atopic dermatitis
  • Seborrheic dermatitis
Treatment
  • Conservative
    • emollients
      • indications
        • for all patients
  • Medical
    • topical corticosteroids
      • indications
        • first-line and often used in combination with topical calcipotriene
          • note that systemic steroids are avoided due to likely flare up of psoriasis while tapering
    • topical calcipotriene (vitamin D analog)
      • indication
        • first-line and often used in combination with topical corticosteroids
    • systemic non-biologic therapies
      • indications
        • moderate-to-severe psoriasis
        • used in combination with topical therapies
      • drugs
        • acitretin
        • methotrexate
        • cyclosporine
        • apremilast
          • especially for those with psoriatic arthritis as well
    • systemic biologic therapy
      • indication
        • moderate-to-severe psoriasis
      • drugs
        • tumor necrosis factor inhibitors
          • adalimumab
          • etanercept
          • infliximab
        • anti-interleukin agents
          • brodalumab
          • secukinumab
          • ustekinumab
    • narrowband ultraviolet B
      • indication
        • for patients who are contraindicated to systemic therapy or who want to avoid systemic side effects
Complications
  • Cardiovascular disease
    • psoriasis patients are at higher risk
 

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