Sterol and Isoprenoid Disease Research Consortium: Smith-Lemli-Opitz Syndrome

Overview

The purpose of this study is to learn about Smith-Lemli-Opitz Syndrome (SLOS). SLOS is an inherited condition that is caused by the body not making an enzyme as it should. The body needs the enzyme to help make cholesterol. SLOS can cause many health problems including slow growth and development, eating disorders, sleep disorders, behavior disorders, and eye diseases. Severe SLOS leads to birth defects and mental retardation and in many cases early death. The investigators plan to measure cholesterol and other sterol levels, perform clinical observations, whole body testing and imaging (brain MRIs), to learn more about the disease and its progression, differences in the clinical features among individuals with SLOS, and look at the effect of cholesterol supplementation in this condition. The study is an interventional study to characterize disease progression and correlations between clinical, biochemical and physiological features of the disease. The main hypothesis is that dietary cholesterol supplementation does not improve features of SLOS related to the brain (e.g. IQ, behavior).

Smith-Lemli-Opitz syndrome (SLOS) is a disorder of cholesterol synthesis, or production. It is caused by mutations in the DHCR7 gene which encodes for 7-dehydrocholesterol- Δ7-reductase, an enzyme necessary for the production of cholesterol in the body. Affected individuals exhibit multiple malformations and mental retardation. The features of SLOS are thought to be primarily related to cholesterol deficiency and accumulation of cholesterol precursors. However, the clinical phenotype is not well characterized, the biochemical pathogenesis is incompletely understood, and there is no proven therapy for this devastating condition. Thus our primary objective is to better define the clinical and biochemical phenotypes of the disease using a natural history study design. The study will contribute to creating a comprehensive SLOS patient registry, identify biomarkers that can be used for diagnostic testing, screening and outcome measures in future therapeutic trials. All patients with SLOS receive dietary cholesterol supplementation with the hope that cholesterol supplementation will improve the clinical manifestation of the disease. However, there is no evidence supporting a clinical benefit of cholesterol supplementation. Thus a secondary objective of the study is to determine if cholesterol intake correlates with changes in whole body cholesterol homeostasis and clinical end-points.