Psoralen/UVA treatment and chromosomes. II. Analyses of psoriasis patients.

Five psoriasis patients treated with 8-methoxypsoralen and UVA (PUVA) were studied by lymphocyte cultures at the 1st, 5th, 10th and 20th treatment and at a maintenance treatment 6 months later. Abnormal amounts of chromosome aberrations were not found, and the frequency of sister chromatid exchange (examined at the last treatment) was not increased. In vitro experiments with nanogram doses of psoralen (similar to plasma levels in patients) showed no increase in chromosome aberration or SCE freqency. The results indicate that therapeutic doses of PUVA have no clastogenic effect.