Cutaneous vitamin D3 formation in progressive systemic sclerosis.

Progressive systemic sclerosis (PSS) is a predominantly dermal disorder which may be associated with epidermal atrophy. We investigated epidermal function in 8 patients with PSS and their healthy controls matched for age, sex and racial group. We measured the vitamin D3 photosynthetic response to whole body irradiation with ultraviolet light B (UVB). There were no significant differences in basal serum vitamin D3 levels (mean +/- SEM: PSS 1.2 +/- 0.2 ng/ml; controls 0.8 +/- 0.1 ng/ml; p greater than 0.1) or post UVB blood values (PSS 5.2 +/- 1.4 ng/ml; controls 6.9 +/- 1.1 ng/ml; p greater than 0.1); although the increases post-UVB were significant in both groups (p less than 0.01). In an additional group of 19 patients with PSS and their corresponding matched healthy controls, we performed determination of random levels of the active vitamin D metabolites, 25-hydroxyvitamin D (25-OH-D) and 1,25-dihydroxyvitamin D [1,25-(OH)2-D]. Similar levels were observed in both groups: 25-OH-D PSS 28 +/- 3 ng/ml, controls 29 +/- 3 ng/ml; 1,25-(OH)2-D PSS 27 +/- 2 pg/ml, controls 31 +/- 2 pg/ml (p greater than 0.1). None of the correlations between skin area involved and vitamin D3 formation or active circulating metabolites reached statistical significance (p greater than 0.1). We conclude that global epidermal synthesis of vitamin D is retained in PSS and, that the hepatic and renal vitamin D hydroxylating mechanisms function normally in that condition.