A Novel Mutation of the DHCR7 Gene in a Sicilian Compound Heterozygote with Smith-Lemli-Opitz Syndrome

INTRODUCTION: Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol biosynthesis, resulting from deficient 7-dehydrocholesterol reductase (3beta-hydroxysterol Delta7-reductase) activity, the enzyme responsible for conversion of 7-dehydrocholesterol to cholesterol. SLOS is most common among people of European descent, with a reported incidence of 1 per 20,000-60,000 newborns, depending on the diagnostic criteria and the reference population. More than 80 different mutations have been identified in several hundred patients. In Italy, SLOS appears to be a rare condition, probably because of underdiagnosis. METHOD: We analyzed by direct sequencing the 7-dehydrocholesterol reductase gene (DHCR7) in a Sicilian patient with Smith-Lemli-Opitz syndrome and his parents in order to characterize the molecular defect. RESULTS: The molecular analysis of the coding exons and the intron-exon boundaries of the DHCR7 gene demonstrated the presence of two missense mutations: a novel mutation (I251N) and a known mutation (E288K) responsible in a compound heterozygous state for a severe form of SLOS. CONCLUSION: The present study describes a Sicilian patient, a carrier of a novel mutation of the DHCR7 gene (I251N), which is responsible in a compound heterozygous state for a severe form of SLOS.