The effects of long-term local PUVA treatment on collagen metabolism in human skin.

The effect of photochemotherapy on skin collagen metabolism was investigated in 57 patients with psoriasis. Twenty-eight patients were treated with trioxsalen baths and UVA irradiation, nine with ditranol and UVB irradiation, and 20 untreated psoriasis patients served as controls. No significant changes were found between the treated groups and the control group in urinary hydroxyproline excretion, skin hydroxyproline content, or in the activities of two enzymes catalyzing collagen biosynthesis, prolyl hydroxylase, and galactosylhydroxylysyl glucosyltransferase in the skin. When the same parameters were compared with the cumulative doses of UVA irradiation, skin prolyl hydroxylase activity slightly decreased with increasing UVA doses, whereas no changes were found in skin hydroxyproline content or galactosyl-hydroxylysyl glucosyltransferase activity. It was concluded that long-term local PUVA therapy does not significantly alter collagen metabolism in the skin.