Psoralen photochemotherapy

Psoralens must be photoactivated by long-wavelength ultraviolet light in the range of 320-400 nm (ultraviolet A [UVA]) to produce a beneficial effect. Psoralens intercalate with DNA and, with subsequent UVA irradiation, cyclobutane adducts are formed with pyrimidine bases. Both monofunctional and bifunctional adducts may be formed, the latter causing interstrand cross-links. These DNA photoproducts may inhibit DNA synthesis. The major long-term risks of psoralen photochemotherapy are cataracts and skin cancer. 

Stern R. Metastatic squamous cell cancer after psoralen photochemotherapy. Lancet 1994 344(8937) 1644-5. 

Gunnarskog JG, Kallen AJ, Lindelof BG, Sigurgeirsson B. Psoralen photochemotherapy (PUVA) and pregnancy. Arch Dermatol 1993 129(3) 320-3. 

Morison WL, et al. Oral psoralen photochemotherapy of atopic eczema. Br J Dermatol 1978 98 25. 

In a clinical study, 15 patients (Group A) with chronic plaque psoriasis were treated with increasing concentrations (1-4%) of topical coal tar paste (Gilmour et al. 1993). These patients did not receive ultraviolet (UV) therapy and served as controls. Seventeen subjects (Group B) received UV-B phototherapy and four subjects (Group C) received psoralen photochemotherapy (PUVA). Another... 

Potapenko, A.Ya., Butov, Y.S., Levinzon, E.S., Mamedov, I.S., Kyagova, A.A., and Nikonenko, B.V., Psoralen photochemotherapy of eczema without UVA-irradiation of patients, presented at 13 International Congress on Photobiology, San Francisco, California, July 1-6, 2000, Abstract 508. 

---