Key result
Despite high 7-DHC levels, circulating vitamin D metabolites in SLOS patients were not significantly different from matched controls, suggesting protection from vitamin D intoxication.
Why the study?
Do patients with Smith-Lemli-Opitz syndrome have abnormal vitamin D metabolism compared to matched controls?
Case-Control (n=15)
Do patients with Smith-Lemli-Opitz syndrome have abnormal vitamin D metabolism compared to matched controls?
Patients with Smith-Lemli-Opitz syndrome appear to have a unique vitamin D metabolism that protects them from vitamin D intoxication despite high levels of the precursor 7-DHC.
May not alter vitamin D management in SLOS; leaves open confirmation of protective mechanism against intoxication.
Smith-Lemli-Opitz syndrome (SLOS) is an inborn error of cholesterol biosynthesis characterized by developmental delay and multiple malformations. Some of the patients have skin photosensitivity and therefore tend to avoid direct exposure to sunlight.SLOS patients typically have low concentrations of cholesterol and abnormally high concentrations of its precursor 7-dehydrocholesterol (7-DHC) in biological fluids and tissues. 7-DHC is also a precursor in the cutaneous synthesis of vitamin D. Sunlight exposure plays a major role in this pathway and reactions transforming 7-DHC into vitamin D and then into 25-hydroxyvitamin D are known not to be specifically regulated. The aim of this study was to evaluate vitamin D status in SLOS patients. We measured 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D serum concentrations and markers of calcium metabolism in five SLOS patients. Despite abnormally high concentrations of 7-DHC, circulating concentrations of vitamin D metabolites were not significantly different from appropriate controls matched for sex, age and season of blood collection. The analysis of historical serum samples stored in our laboratory from the same cases plus 10 other SLOS patients further supported these findings. Our data suggest that SLOS patients have a peculiar vitamin D metabolism that protects them from vitamin D intoxication. This appears to be due in most cases to decreased transformation of 7-DHC into 25-hydroxyvitamin D, perhaps depending on reduced sunlight exposure as a consequence of photosensitivity. Possible alternative mechanisms are discussed.
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Rossi et al. (2005) conducted a case-control in Smith-Lemli-Opitz syndrome (n=15). Smith-Lemli-Opitz syndrome vs. Controls matched for sex, age and season of blood collection was evaluated on Circulating concentrations of vitamin D metabolites (25-hydroxyvitamin D and 1,25-dihydroxyvitamin D). Despite high 7-DHC levels, circulating vitamin D metabolites in SLOS patients were not significantly different from matched controls, suggesting protection from vitamin D intoxication.
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