Vitamin D metabolites in generalized scleroderma: evidence of a normal cutaneous and intestinal supply with vitamin D

Vitamin D metabolites in serum were analysed in 20 patients with generalized scleroderma. The concentration of 1,25-dihydroxyvitamin D was normal, however, significantly lower concentrations (p less than 0.05) were found in 7 patients with cutaneous calcinosis in comparison with 13 patients with no calcinosis. Concentrations of 25-hydroxyvitamin D, 24-25-dihydroxyvitamin D, and vitamin D-binding protein (Gc globulin) were all within the normal range. The 24,25-dihydroxy-vitamin D level correlated with the duration of disease (r = 0.4453, p less than 0.05), and 25-hydroxyvitamin D tended to correlate (r = 0.3016, NS). The study strongly indicates that cutaneous synthesis, intestinal absorption and hepatic hydroxylation of vitamin D are not deficient in scleroderma. A relative but specific decrease in the renal hydroxylation to 1,25-dihydroxyvitamin D, i.e. the active hormone, as the disease progresses and calcinosis occurs, is suspected.