Narrowband UVB phototherapy for psoriasis: Results with fixed increments by skin type (as opposed to percentage increments)

Many authors currently advocate 10-20% dosage increments between phototherapy sessions when treating psoriasis with narrowband ultraviolet B (UVB). However, such regimens are associated with a risk of significant erythema. In order to reduce this risk, a fixed increment regimen was developed using increments ranging from 30 mJ/cm2 for skin type II to 150 mJ/cm2 for type VI. Starting doses, also based on skin type, range from 180 to 400 mJ/cm2. Data from 20 patients with moderate to severe plaque psoriasis [13 male, 7 female, age range 17-74, skin types II (3), III (10), IV (3), V (1), VI (3)] completing 27 courses of phototherapy of more than 3 weeks' duration between 8/96 and 12/97 were compared. Complete, or near-complete clearing occurred in 8/13 courses (62%) with a frequency of attendance (during the initial 24 sessions) of >2.5 sessions per week, 4/8 (50%) with a frequency of 2.0-2.5, and 1/6 (17%) with a frequency of <2.0. In the subset of patients taking low-dose oral retinoids, rates of clearing were higher. Overall, 10 of 20 patients (50%) cleared, usually within 24-30 sessions. The average maximum dosage in such cases was 1400 mJ/cm2. There were only 13 instances of minor erythema, and 1 instance of severe erythema resulting in desquamation and requiring interruption of treatment. This was due to the inadvertent administration of an excessive 300 mJ/cm2 increment to a type VI patient. In summary, using a conservative fixed increment regimen, clearing of psoriasis is possible while minimizing the risk of serious erythema. Results are enhanced when patients attend 3 phototherapy sessions per week.