Identifying and Genotyping Homozygous Familial Hypercholesterolemia (HoFH) Patients

This is a non-interventional study; no investigational product is administered in this study. Information collected in this study may be used to identify potential participants for clinical gene therapy trials in HoFH. The investigator will discuss the study with participants who have a clinical presentation consistent with HoFH and where possible, the treating physician, in order to assess their interest to participate. After informed consent has been obtained, participants will be asked to provide a blood sample (up to 40 mL) for genotyping to confirm genetic diagnosis of HoFH due to mutations in LDLR, a lipid panel and anti-AAV8 NAb titer. Participants and, whenever possible, their treating physician will complete a medical history questionnaire and provide supporting documentation. The informed consent form (ICF) and data collection methods may vary depending whether the informed consent is obtained remotely or at a participating study site. Information collected will include the following: * patient demographics (age, sex, weight) * medical history * previous genotype results (if available) * results of most recent lipid panel(s) * use of lipid lowering therapies, including failure to respond * assessment of presence of liver disease, including history of hepatitis B and C, human immunodeficiency virus (HIV), cirrhosis, and alcohol use Once this information is received by the investigator and Sponsor, a preliminary assessment of confirmation of a diagnosis of HoFH will be performed. Participants and/or their treating physician will be informed of the results of the genetic testing. All participants will be provided an opportunity to speak with a genetic counselor upon receiving the results of the genetic testing. Data collected in this study may be used to identify potential candidates for separate clinical trial(s) using gene therapy.