Smith-Lemli-Opitz Syndrome and Cholic Acid

Inclusion Criteria: * Ages 2-25 years. * Participants (or their parents/legally-authorized representative) must provide signed informed consent. * Assent must be obtained from those participants ages 7-17 years who are intellectually capable of understanding this study. * Diagnosis of SLOS based on clinical features and biochemical + genetic confirmation. * Participants are capable of traveling to the STAIR study site. * Fasting plasma cholesterol ≤125 mg/dL during the Qualification Phase must be established before starting cholic acid therapy. * Clinically stable at the time of enrollment * Participants must be on a constant dietary cholesterol intake for at least 3-months prior to treatment with cholic acid. * Participants must agree to make no changes in cholesterol supplementation during the STAIR study. * SLOS participants who are taking antioxidants will be included. Participants must agree to make no changes in the antioxidant dose during this study. * For females of childbearing age (who have begun menstruating), a negative pregnancy test must be documented at the start of the study (week 0/ baseline) and at the end of cholic acid administration (week 8). Exclusion Criteria: * Participants are unable to provide signed informed consent and/or verbal assent. * Participants have an unstable clinical condition that would prevent completion of the study. Medically unstable participants would include those with severe liver disease, complex birth defects such as severe h…