Psoriasis is a chronic inflammatory disease involving multiple organ systems and affecting approximately 3.2% of the worlds population. The 2019 guidelines for the management and treatment of psoriasis focused on the discussion on ultraviolet (UV) light-based therapies – including narrowband (NB) and broadband (BB) UVB; UVA in conjunction with photosensitizing agents; targeted UVB treatments such as with an excimer laser; and several other modalities and variations of these core phototherapies, such as newer applications of pulsed dye lasers, intense pulse light and light-emitting electrodes. Few recommendations are enlisted below:

• Patients receiving NB-UVB treatments, twice a week, achieve clearance in a mean of 88 days compared to 58 days in those receiving three such sessions every week.
• Application of a thin layer of emollient, such as petrolatum, is recommended before NB-UVB treatment sessions, as this increases treatment effectiveness in psoriasis and also reduces UV-induced erythema.
• However, thickly applied emollient may decrease UVB transmission and potentially diminish efficacy.
• Estimation of initial NB-UVB dose must be performed by skin type:
  • Skin-type I and II – 300 m J/cm²
  • Skin-type III and IV – 500 m J/cm²
  • Skin-type V and VI – 800 m J/cm²
• In subsequent visits, the patient response to phototherapy is assessed by the degree and duration of skin erythema and possible subjective symptoms of burning – stinging, pain or itch.
• The effect of skin erythema on UVB dosing will be as follows:
  • Minimal erythema lasting 24 hours following treatment – increase dose by 20%.
  • Erythema persistent for 24 hours, up to 48 hours – dose held at previous level until erythema lasting for 24 hours.
  • Erythema lasting for 48 hours – no treatment on that day, followed by return of dose to the last lower dose that did not cause persistent erythema.
• Once psoriasis clears, the patient may choose to continue maintenance therapy as a taper or indefinitely. The maintenance dose should be the last dose given prior to clearing.
• The maintenance therapy taper protocol is treatment twice weekly for 4 weeks and then once weekly for 4 more weeks. The dose should be held constant.
• For prolonged maintenance therapy, the patient should receive a treatment every 1-2 weeks. The final dose should be decreased by 25% and held constant for all maintenance treatments.
• Regardless of the Fitzpatrick skin type, the maximum dose for treatment of facial areas should not exceed 1 J/cm2. Dosing may be increased, typically at 5-10% at each treatment as tolerated, if the skin is not clear.
• Higher doses should be prescribed by a physician’s order, based on the individual patient’s conditions. The recommended maximum dose of phototherapy is as follows:
  • Skin-type I and II – 2000 mJ/cm²
  • Skin-type III and VI – 3000 mJ/cm²
  • Skin-type V and VI – 5000 mJ/cm²

• Although psoralen and ultraviolet A (PUVA) monotherapy is found to be more effective than NB-UVB in many studies, the superior short-term and long-term safety, simplicity and lower cost make NB-UVB as the preferred treatment for plaque psoriasis.
• NB-UVB is also preferred over BB-UVB (vide infra), owing to the increased efficacy, quicker treatment response and lower rates of adverse effects.

Source: Journal of the American Academy of Dermatology. 2019 Sep;81(3):775-804. doi: 10.1016/j.jaad.2019.04.042.