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