B12. Photodermatoses and phototherapy

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Photodermatoses

  • Photodermatoses – skin diseases that develop due to light exposure
  • Photodermatoses of unknown origin
    • Solar dermatitis = sunburn
      • UVB radiation causes apoptosis of keratinocytes -> release of inflammatory cytokines
      • Clinical features
        • Pruritus, pain
        • Erythema, oedema
        • Blisters (severe)
      • Treatment
        • Wet compress
        • Cooling ointments
        • Topical steroids
    • Polymorphous light eruption (PLE)
      • Chronic disease
      • In adult females
      • Most common photodermatitis
      • Clinical features
        • Itching, burning erythema
        • Malaise, headache
    • Solar urticaria
      • Rare
      • Type I hypersensitivity
      • Urtica at site of sun exposure
    • Actinic prurigo
    • Chronic actinic dermatitis
  • Photodermatoses of known origin
    • Phototoxic reactions
    • Photoallergic reactions
  • Diagnosis
    • Photo-patch test
      • UVA applied, then patch
      • Read immediately, then at 24, 48, 72 hours
    • Photo-provocation test
      • Differentiate between solar urticaria, chronic actinic dermatitis, polymorphous light eruption, SLE
  • Treatment
    • Photohardening
    • Photoprotection

Phototherapy

  • Indications
    • Psoriasis
    • Atopic dermatitis
    • Alopecia areata
    • Granuloma annulare
    • Cutaneous T-cell lymphoma
    • Vitilligo
    • Photodermatoses
    • BCC
    • Actinic keratosis
  • Mechanisms
    • Thickens epidermis
    • Hyperpigmentation
    • Immunosuppressive effect
    • Anti-tumor effect
  • Procedure
    • Minimal erythematous dose (MED) is determined
    • The dose of UV light depends on the MED
  • Types
    • Narrow-band UVB
    • Broad-band UVB
    • Selective UVB
    • Psoralen + UVA
    • Photodynamic therapy
      • Uses visible light, not UV
      • For cancers that are caused by UV (BCC)