Psoriasis and vitamin A

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Abstract
The vitamin-A status of 107 patient with psoriasis and 37 healthy controls was investigated. The mean serum level of retinol-binding protein (RBP) was normal in the 79 patients with chronic plaque psoriasis covering 25% or less of the skin surface. In the 28 patients with more extensive plaque lesions or pustular/ erythrodermic psoriasis, the mean serum RBP level was significantly lower than in the controls (P1), dehydroretinol (vitamin A2) and carotenoids were measured in extracts of saponified shave-biopsy specimens of uninvolved and involved skin from 33 patients with plaque psoriasis. Their retinol values did not differ significantly from those found in control skin (mean, 252 ng/g), whereas the carotenoid levels in both uninvolved and involved skin were 25%–50% lower. In contrast, the dehydroretinol concentration was higher in the patients' involved skin (mean, 237 ng/g) than in their uninvolved skin (94 ng/g) and healthy control skin (70 ng/g; P<0.01). Although the origin of increased dehydroretinol levels in involved psoriatic skin is unknown, similar increments were observed in control epidermis in which proliferation had been induced by tape stripping. In 7 patients treated with oral etretinate (aromatic retinoid) for 2–3 weeks, the median retinol and dehydroretinol levels in involved skin increased by 107% and 212%, respectively; the vitamin-A concentrations in uninvolved skin did not change significantly. Oral treatment with β-carotene/canthaxanthin raised the median carotenoid levels in uninvolved and involved skin by 170% and 610%, respectively, without significantly affecting the vitamin-A composition.