Psoriasis

Chronic, inflammatory, multisystem disease with predominantly skin and joint manifestations.

Background/Epidemiology

  • Common- 1.3-2.2% of the UK population
    • More common in white people; most likely to present between 15 and 30 years or after 40 years; 1:1 M:F ratio

Aetiology/Pathophysiology

  • ?Triggers
    • Streptococcal infection (Guttate psoriasis); Drugs; sunlight; trauma (Koebner reaction)
    • Stress
    • Alcohol/smoking
    • Change in environment
  • Genetic factors
  • Regardless of the cause, psoriasis seems to be characterised by T cell infiltration of the epidermis.
    • Results in proliferation of keratinocytes (causing plaques in which there are immature keratinocytes) and release of inflammatory mediators (causing inflammation)

Presentation

  • Characterised by red, scaly (white/silver appearance) patches of skin; usually well-defined edges; often symmetrical in distribution
  • The extent and distribution of plaques can help classify psoriasis into the following
    • Chronic Plaque Psoriasis
      • Scalp, trunk, buttocks and extensor surfaces (elbows/knees)
      • Can be single, few or multiple (often symmetrical- may coalesce to form larger lesions)
      • Oval/irregular; >1cm; clearly defined border
    • Scalp psoriasis (may cause scarring alopecia)
    • Facial psoriasis
    • Flexural psoriasis
    • Nail psoriasis
      • Nail changes include pitting, orange/yellow discolouration; subungual hyperkeratosis; onycholysis
    • Guttate psoriasis
      • Usually present in children/young adults and may be a first presentation or associated flare of chronic plaque psoriasis
      • Characterised by widespread (trunk and proximal limbs), small (2mm-1cm) scaly papules
    • Pustular Psoriasis
      • Localised (commonly palmoplantar pustular psoriasis)
        • Hands/feet; yellow-brown pustules within plaques/redness/scaling
        • More common in women and occurs 40-50 years
      • Generalised
        • DERMATOLOGICAL EMERGENCY
        • Rarely, rapidly developing widespread redness and pustule eruption can occur, often with systemic symptoms e.g. fever, malaise, tachycardia, weight loss, arthralgia
    • Erythrodermic psoriasis
      • >90% of the body is red with various degrees of scaling (often poorly defined)
      • Medical emergency requiring urgent care
      • Often patients are systemically unwell

Assessment

  • If possible, use patient questionnaires to assess severity, impact on quality of life
  • Also assess any joint involvement (psoriatic arthritis)

Management

  • 1st line
    • Topical preparations
      • Which preparation?
        • Creams, lotions, gels for widespread disease
        • Lotions, solutions, gels for scalp disease
        • Ointments for thick scale
      • Emolients and tar preparations
      • Vitamin D preparations (calcipotriol ointment)
        • May cause irritation (alternatives include calcitriol)
      • Moderately potent or potent steroid can be considered if unresponsive to vit D alone
        • NB You can get combination preparations e.g. Dovobet (betamethasone 0.05% + calcipotriol 50mcg/g)
        • Steroids should only be used in localised (<10% of total body surface) disease.  Potent steroids should only be used short term
      • Rarely, dithranol can be used if there are just a few, large plaques
      • For hyperkeratotic plaques, consider the addition of salicylic acid preparations e.g. Diprostatic
  • 2nd line
    • Phototherapy (narrow band UVB and PUVA)
  • 3rd line
    • Biological agents (adalimumab, eatnercept)
      • Only really used in patients with systemic disease e.g. psoriasis with arthritis
    • Methotrexate may be used prior to this in patients with psoriatic arthritis and plaque psoriasis

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