The Smith-Lemli-Opitz syndrome (SLOS) is caused by deficiency of 7-dehydrocholesterol-D 7 -reductase, an essential enzyme in the biosynthesis of cholesterol. Affected patients have low seru m concentrations of chole- sterol and elevated cholesterol precursors, 7-dehydrocholesterol (7-DHC), 8-dehydrocholesterol and 19-nor- 5,7,9(10)-cholestatrienol. A simple and rapid ultraviolet spectrophotometric (UVS) m ethod for detection of serum 7-DHC is described. Samples of 15 patients with clinical suspicion of SLOS and samples of 6 patients without symptoms of SLOS were assessed. Absorption maxima characteristics of 7-DHC (lmax 272, 282, and 292 nm) were observed in 8 patients’ sera but not in controls. In 8 patients’ sera the diagnosis was confirmed biochemically by gas chromatographic mass spectrometric (GC/MS) analysis of serum sterols. UVS measurement of 7-DHC correlated well with GC/MS profiles. The UVS assay is cheap and easy method for rapid detection of SLOS in general clinical biochemical laboratories.

        Key words: Smith-Lemli-Opitz syndrome, screening, 7-dehydrocholesterol, ultraviolet spectrophotometry,