Photodermatology Flashcards
What is the Soret band?
What is its relevance?
408nm
All cutaneous porphyrias are aggravated by light at this wavelength
It is the excitation peak for protporphyrin IX
ALA is activated by light at this wavelength
What are the wavelengths of UV UVC UVB UVA Commission Internationale de l’Eclairage (CIE) definitions
UV - 100-400nm UVC 200-280nm UVB - 280-315nm UVAII (near UVA) - 315-340nm UVAI (far UVA) - 340-400nm NB. Wavelengths shorter than about 200 nm propagate only in a vacuum and are not relevant to phototherapy
What wavlength is narrowband UVB (TL01)?
311nm
What wavelength is the Wood’s lamp?
365nm
Use the Wood’s lamp everyday of the year!
What wavlengths are used for PDT with
ALA?
Metvix (MAL)?
ALA - 408nm - Soret band, blue light
MAL - 570-670, peak at 635nm - red light: 635 backwards looks like REd
What wavlength is used for PUVA?
What is the wavelength of therapeutic UVA1 light?
Peak at 320-330nm (UVAII)
UVA1 340-400nm
What is the risk of skin cancer from PUVA?
14x increased risk of cutaneous SCC in patients who have received >200 PUVA treatments or >2000J /cm2
Also evidence of increased risk for melanoma in these PUVA patients
PUVA lentigines indicate higher risk of PUVA-related skin cancers
>200 phototherapy treatments (of any kind) is PBS contraindication for phototherapy in Biologics work up
No evidence that UVB phototherapy increases skin cancer but probably does
How is PUVA dosed?
Oral;
8MOP 10mg tablets
0.6mg/kg 2 hours before UVA (more accurate to use 25mg/m2 - use a calculator to get body sruface area)
max dose 60mg
Topical PUVA;
0.01-0.1% creams
apply for 10-30min before UVA
Sun block surrounding non-involved areas
Bath PUVA;
1% 8-MOP solution (10mg/mL) prepared
Add 37mls to 100L bath to make 3.7mg/L solution
Some use lower conc of 2.6mg/L or 1.0mg/L
Ensure bath at 37degreesC
Soak for 15-20 min then briefly pat dry and immediately start UVA
UVA is dosed in J/cm2 with starting doses around 0.5-3.0 or 70% of MPD
What is the standard erythema dose?
The duration of exposure at 100J/m2 required to turn the skin red
What is the Minimal erythema dose (MED)?
How is it determined?
The lowest irradiance required to produce erythema after 24 hrs
Adjacent areas of skin on back/buttock is exposed to the same wavelength of light for different durations (usually 10,12,14,16,20 mins). The intenisties of the light used for testing is based on SPT
after 24 hrs the area with the slightest visible erythema determines the MED
What is the Minimal phototoxic dose?
The same as MED but for PUVA - the reading is done 4 days after exposure rather than 24hrs
How is nbUVB (TL-01) started based on MED?
Start with 70% MED
10-20% increments each visit
What’s Goeckermans regime
Bath in coal tar
UVB
Coal tar
What’s Goeckermans regime
Bath in coal tar
UVB
Coal tar
