INCLUSION CRITERIA:  Males or females of any age with any one of the following:  Clinical, biochemical, or genetic diagnosis of Smith-Lemli-Opitz Syndrome OR Clinical, biochemical, or genetic diagnosis of desmosterolosis, lathosterolosis, CHILD syndrome, X-linked dominant chondrodysplasia type2 or another inborn error of cholesterol synthesis OR Clinical suspicion of an inborn error of cholesterol synthesis, metabolism or impaired cholesterol homeostasis. Clinical observations may include, but are not limited to lipid-laden macrophages, abnormal LDL, HDL, total cholesterol, triglycerides, abnormal lipid electrophoresis, lipid storage in other tissues. OR Family members of individuals diagnosed with or suspected to have an inborn error of cholesterol synthesis, metabolism or homeostasis.  EXCLUSION CRITERIA:  Individuals who cannot travel to the NIH because of their medical condition will be excluded from on-site participation. They may participate in the telemedicine or in the biomaterials parts of the study. Individuals who, in the opinion of the investigator, are unable to comply with the protocol or have medical conditions that would potentially increase the risk of participation will be excluded from on-site participation. They may participate in the telemedicine or in the biomaterials parts of the study. Female participants who are pregnant will be excluded from evaluations requiring sedation, radiation and LP. Total blood draw volumes will be kept at a minimum or if anemia of pregnancy is known, no blood will be taken for research testing.