Skin content of 7-dehydrocholesterol in patients with malabsorption.

The mechanism for the development of vitamin D deficiency in patients with malabsorption remains unclear. We wished to examine the hypothesis that one factor was a reduced skin content of 7-dehydrocholesterol, the precursor for the formation of vitamin D in the presence of ultraviolet radiation. We measured 7-dehydrocholesterol in skin samples from 9 patients who had previously had vitamin D deficiency due to malabsorption (6 with Crohn's disease, 2 with primary biliary cirrhosis, and 1 with idiopathic pseudo-obstruction). We found no evidence of reduced levels of 7-dehydrocholesterol in the skin in these patients. Lack of 7-dehydrocholesterol does not contribute to vitamin D deficiency in malabsorption.