The British journal of dermatology
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The variation in erythemal sensitivity of the skin during PUVA therapy with oral 8-methoxypsoralen (8-MOP) was examined by measuring both UVA and PUVA erythemal responses, together with plasma 8-MOP concentration, in 27 patients about to start PUVA therapy for psoriasis. The erythema responses were judged visually, and also measured using a reflectance instrument in order to construct dose-response curves. No significant association was found between the UVA and PUVA minimal erythema responses. ⋯ The slopes of the UVA and PUVA erythema dose-response curves were significantly associated, and this association became much stronger when allowance was made for plasma psoralen concentration. These results show that erythemal sensitivity during PUVA therapy is related to both plasma psoralen concentration and inherent UVA sensitivity, but that this relationship is not apparent when sensitivity is judged visually as the minimal erythema response. The association between PUVA and UVA erythemal sensitivity suggests a common pathway in the vascular response induced by UVA radiation, with or without psoralen.
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This study assesses the variability of two non-invasive methods of measuring stratum corneum barrier function in vivo. Transepidermal water loss (TEWL), and the vascular response to hexyl nicotinate (HN) penetration as determined by laser-Doppler flowmetry, were measured in a group of 21 healthy volunteers. Each time profile of the vascular response to HN penetration was analysed using the following parameters: the baseline cutaneous blood flow, the lag-time between application and initial response (t0), the time between application and maximum response (tmax), the maximum response, and the slope of the curve. ⋯ The intra-individual reproducibility of t0 and tmax. for HN penetration was also high (relative differences of 2.8 and 3.1%, respectively). The other vascular response parameters were less reproducible (relative differences of 6.9-18.6%). We conclude that TEWL and selected parameters of HN penetration, as non-invasive tests of the stratum corneum barrier function, yield reproducible results and are hence useful for investigations assessing the skin barrier function in various disorders.
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In the U. K., PUVA treatment for psoriasis is usually given three times weekly, with the starting dose of UVA chosen according to the skin type of the patient. Observations on the time-course and dose-response characteristics of PUVA erythema suggest that larger doses of UVA could be used safely, provided that the frequency of PUVA treatment is reduced. ⋯ These results compare favourably with previous studies in which treatment was given three or four times weekly. Thus, twice weekly PUVA treatment for psoriasis is at least as effective as treatment given more frequently, and may be safer, as lower cumulative UVA doses are required for clearance. It also allows for more efficient operation of a PUVA unit and is more convenient for patients.
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Clinically we have noted that the skin of patients treated with long-term oral etretinate becomes uniformly soft and smooth to touch, like facial skin that becomes smoother and less wrinkled following treatment with topical tretinoin. This suggests that retinoids, whether used systemically or topically, alter the physical properties of the skin, particularly of the stratum corneum (SC). To study the influence of retinoids on the SC, we serially assessed the functional properties of the SC non-invasively in retinoid-treated humans and experimental animals. ⋯ Systemic administration of high-dosage etretinate, 4 or 8 mg/kg/day, to guinea-pigs also induced dose-dependent increases in both SC hydration and TEWL measured on the plantar skin after 1 month. Moreover, in the animals given etretinate 4 mg/kg/day we confirmed a slight but significant decrease in the number of cell layers of the plantar SC. Likewise, patients with various dermatoses began to show similar functional changes of the SC in the uninvolved skin of the flexor surface of the forearms 3 weeks after the start of oral etretinate treatment, consisting of 50 mg daily for 2 weeks, followed by gradual dose tapering.(ABSTRACT TRUNCATED AT 250 WORDS)