B12. Photodermatoses and phototherapy
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
- Solar dermatitis = sunburn
- 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
- Photo-patch test
- 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)