A1. Psoriasis

• A type of systemic papulosquamous dijusease
• Epidemiology
  • 2% of whites, less common in other skin colours
  • 20 – 40 years
    • Family history
  • 50 – 100 years
    • No family history
• Etiology
  • Polygenic inheritance (HLA)
  • Triggers
    • Streptococci URTI
    • Irritation of skin
    • Staph
    • HIV
    • Mechanical irritation
    • Alcohol
    • Stress
    • Drugs
      • Beta blockers
      • Lithium
      • Interferon
      • Chloroquine
• Pathophysiology
  • Acanthosis
    • Hyperplasia of stratum spinosum
    • Elongated rete ridged
  • Parakeratosis – nuclei retention
  • Hyperkeratosis
  • Munro microabscesses
  • T-cell secreted cytokines
  • Overexpression of beta-defensin -> no secondary superinfection
• Clinical features
  • Symptom-free intervals with relapsing
  • Lesions
    • Well-demarcated
    • Salmon-coloured erythematous, silvery scaling plaques
    • Mainly on scalp, back and extensor surfaces
      • Elbow
      • Knees
      • Scalp
      • Gluteal cleft
    • Pruritus
  • Nail involvement
    • Nail pitting (small depressions in nail)
    • Oil drop sign – well-circumscribed yellow-red discoloration
    • Brittle nails
    • Onycholysis – separation of the nail plate
      • Nail separates from the skin below -> becomes grey
  • Psoriatic arthritis
    • 5 – 30% of patients
    • Very debilitating
    • Distal and proximal interphalangeal joints
    • Spine
    • Diagnosis (CASPAR)
      • > 3 of these
      • Psoriasis
      • Psoriatic nail problems
      • Negative rheumatoid factor
      • Dactylitis – sausage finger
      • Radiological signs
    • Treatment
      • NSAIDs
      • DMARDs
• Other forms
  • Guttate psoriasis
    • Drop-sized lesion
    • In children after strep
  • Inverse psoriasis
    • Skin folds and flexor surfaces
• Diagnosis (mostly clinical)
  • Auspitz sign – pinpoint bleedings when scales are scraped off
  • Koebner phenomenon – skin damage causes psoriasis to appear there
  • Skin biopsy – rarely needed
    • Parakeratosis
    • Munro microabscesses
    • Acanthosis
• Differential diagnosis
  • Atopic dermatitis/atopic eczema
    • Poorly demarcated
    • Severe pruritus
    • Exudative, not dry
    • Flexor surfaces
  • Seborrheic dermatitis
    • Greasy-looking yellow scales
    • On face and trunk
• Treatment
  • Moisturizer
  • Avoid nicotine, alcohol
  • Topical
    • Steroids
      • Triamcinolone
      • Fluocinonide
      • Clobetasol
    • Vitamin D derivatives
      • Calcipotriene
    • Tar preparations
    • Retinoids
  • Systemic
    • MTX
    • Retinoids
    • Cyclosporine
  • Biological therapy
    • Adalimumab, infliximab, etanercept – TNF alpha
    • Secukinumab – IL-17
    • Briakinumab – IL-23
  • Phototherapy
    • UVB therapy
      • Narrow-band UVB
    • PUVA (psoralen + UVA)
      • Psoralen increases photosensitivity of skin
      • UVA radiation
• Complications
  • Increased CV risk
  • Metabolic syndrome
  • Kidney disease