This study will investigate the cause and medical problems associated with a group of genetic disorders known as inborn errors of cholesterol synthesis, in which the body does not produce cholesterol. People with this disorder may have birth defects and learning and behavioral problems. People with an inborn error of cholesterol synthesis and related disorders, including Smith-Lemli-Opitz syndrome, lathosterolosis, desmosterolosis, X-linked dominant chondrodysplasia, CHILD syndrome, Greenberg dysplasia, and some cases of Antley-Bixler syndrome, may be eligible for this study. People who are carriers of the disorders also may enroll. Participants and family members will provide blood and urine samples, as well as other tissue samples collected during medically indicated procedures such as biopsy or surgery. These tissues may include, for example, gallstones, cataracts, cerebrospinal fluid, amniotic fluid, lymph tissue, and DNA samples. In rare instances, a skin biopsy may be requested to aid in establishing a diagnosis. Medical information will also be gathered from medical records, photographs, and X-rays.