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Twenty-five psoriatic patients were studied histologically before and after PUVA therapy in order to delineate the relationship between dermal mast cells, psoriasis healing process and collagen changes. A number of mast cells were found in the psoriatic changes. A number of mast cells were found in the psoriatic lesion both before PUVA and also after PUVA therapy in 22 of the 25 patients. Fibrosis of the papillary dermis and upper reticular dermis was found in 3 cases. Increased collagen deposition and increased numbers of fibroblasts were accompanied by verticalization of ectatic and elongated blood vessels, with an overall pattern of relatively recent scarring. Mast cells were no longer detectable in the fibrosis area. We cannot exclude the possibility that PUVA therapy exerts a further stimulus on mast cell histamine and heparin degranulation in this type of psoriasis, thus leading to dermal fibrosis and blood vessel neogenesis.

Long-term PUVA-treated psoriatic patients given maintenance therapy (UVA doses greater than 1,000 J/cm2) have been demonstrated to undergo lymphopenia and a decrease in the total number of circulating CD3+ and CD4+ T cells. The aim of this study was to assess whether the impairment of T cells is detectable also in psoriatic patients after long-lasting PUVA discontinuation. A group of 34 psoriatic patients (25 males, 9 females; mean age 52.7 +/- 12.82 years), who had previously been treated by PUVA therapy (average cumulative dose 1,898.48 +/- 1,207.12 J/cm2), was studied 1 year or more after discontinuation of PUVA therapy. The patients studied failed to show any impairment in CD3+ and CD4+ cells. Nevertheless, a significant increase (p less than 0.05) in circulating CD8+ cells (both in the percentage and the total number) was detectable in PUVA patients as compared to appropriate controls. The significance and implications of this finding are not known and need further investigations.

The relationship between high-dose PUVA treatment in psoriatic patients and peripheral T lymphocyte subsets (total number and percentage) has been studied. Of the two groups of patients considered, the first included 19 patients, all affected by chronic, progressively worsening psoriasis; they had never been previously treated by photochemotherapy. The second group included 13 psoriatic patients, who had received an average cumulative dose of 2,007.69 +/- 1,191.05 J/cm2. The 'long-term' PUVA-treated group was assessed while undergoing maintenance therapy. No significant differences were found between untreated patients and healthy controls for any of the parameters considered. A significant reduction (p less than 0.05) in the total number of lymphocytes in long-term PUVA-treated patients both versus untreated patients and controls was found. Furthermore, long-term PUVA-treated patients showed a significant reduction (p less than 0.05) in the percentage of lymphocytes as compared with controls. The reduction in the total number of CD3+ and CD4+ T cells was, moreover, significant (p less than 0.05) as compared with untreated patients. The impairment of circulating CD3+ and CD4+ T cells (total number) was only on the borderline of statistical significance vis-à-vis controls. These findings suggest the usefulness of a careful assessment of circulating T lymphocyte subsets in patients who undergo long-term PUVA therapy.

Three to four months' PUVA treatment is a widely-adopted procedure to induce psoriasis remission and for the purpose of this study is called "medium-term". The 32 psoriatic patients considered revealed a statistically significant baseline decrease in OKT3+ (p less than 0.001), OKT4+ (p less than 0.001) and OKT8+ (p less than 0.001) as compared with 40 healthy controls, while OKT4/OKT8 was normal. Variance analysis within the psoriatic group failed to reveal further significant variation in the immunological parameters during the 3 months under study. Nevertheless, there was a marked trend towards a reduction in OKT4+ cells and OKT4/OKT8 as compared with baseline values after 3 months. These results suggest that "medium-term" PUVA therapy does not statistically restore the pre-existing baseline changes in T-lymphocyte subsets of the psoriatic patients. The non-statistically significant effects as regards OKT4+ may be due to the small number of patients who reached 3 months' treatment (9 patients) but could be regarded as the first step towards the significant changes described here in long-term PUVA-treated psoriatic patients.