Treatment of psoriasis with oral psoralens and longwave ultraviolet light. Therapeutic results and cytogenetic hazards.

The purpose of the present investigation was to study the usefulness of oral treatment of psoriasis with psoralens and longwave ultraviolet light and the possible cytogenetic hazards of this therapy. 8-methoxypsoralen (8-MOP) in doses between 15 and 60 mg orally followed 2 hours later by UVA irradiation of one side of the body gave a healing of the irradiated side in 24 of 40 cases and an improvment in another 11 cases while only one case healed on the side of body that was not irradiated. The most common undesired side effect was pruritus on the irradiated side of the body. The cytogenetic study showed that 8-MOP and UVA treatment of lymphocytes in vitro gives rise to chromosomal aberrations. In a combined in vivo-in vitro study where the lymphocytes had been isolated from a patient 2 hours after intake of 60-80 mg 8-MOP and then irradiated with therapeutic UVA doses, a significant increase in chromosomal aberrations was found. When chromosome analyses were made on the patients whilst the 8-MOP treatment was temporarily withdrawn and when the lymphocytes were not irradiated in vitro, no increased frequency of chromosomal abberations was found on comparison with a group of psoriatic patients receiving dithranol therapy.