Causes and Natural History of Dyslipidemias

This study will evaluate people with dyslipidemias - disorders that affect the fat content in the blood. Fats, or lipids, such as cholesterol and triglycerides, are carried in the blood in particles called lipoproteins. These particles are involved in causing blood vessel diseases that can lead to conditions like atherosclerosis (hardening of the arteries) or heart attack. Participants will undergo accepted medical tests and procedures to evaluate their condition. Most of the test results are helpful in making a diagnosis and in guiding treatment. People with lipid disorders are eligible for this study. Representative types of patients include those with: * Plasma cholesterol levels greater than 200 mg/dl or less than 120 mg/dl * Plasma LDL-C levels greater than 130 mg/dl or less than 70 mg/dl * Plasma HDL-C levels greater than 70 mg/dl or less than 25 mg/dl * Unusual cholesterol deposits or xanthomas (nodules of lipid deposits on the skin) Children under 2 years of age are excluded from the study. Participants will undergo some or all of the following procedures: \- Plasma evaluation. Apolipoproteins (plasma proteins involved in metabolism of cholesterol, triglycerides, phospholipids, and proteins in the blood) and enzymes involved in lipid metabolism are measured.

* INCLUSION CRITERIA: * Children \>= 2 years of age and \>12 kg and adults * Dyslipidemia subjects of interest group Subject Selection criteria. The study population will include patients who are referred to the Cardiovascular Branch from private care providers or academic institutions with any of the following potential lipid abnormalities or clinical stigmata associated with dyslipoproteinemias: a) increased plasma levels of cholesterol, triglycerides, HDLcholesterol or LDL-cholesterol b) decreased plasma concentrations of cholesterol and HDL-cholesterol c) postprandial hyperlipidemia or d) eruptive xanthomas, xanthelasma, tuberous or tendinous xanthomas, or corneal opacities. The following is a representative list of the types of patient presentations with dyslipidemia and potential diagnoses eligible for this protocol: * Plasma cholesterol levels \>200 mg/dl or \130 mg/dl or \70 mg/dl or \150 mg/dl - includes patients with deficiency of lipoprotein lipase, hepatic lipase or apoC-II, GPIHBP1, LMF1, dysbetalipoproteinemia, Type I, Type IV and Type V hyperlipidemia. Eligibility Evaluation The participant will be evaluated for eligibility on this protocol according to the usual guidelines of medical care. This includes certain minimal risk screening activities that may be performed prior to obtaining assigned informed consent that could include: * E-mail, written, in person or telephone communications with prospective subjects. * Review of existing medical records to include H\&P, laboratory studies such as lipid panels * Review of existing MRI, x-ray, or CT images. * Review of existing photographs or videos. * Review of existing pathology specimens/reports from a specimen obtained for diagnostic purposes. We will follow all relevant federal or state laws, and local institutional requirements, as applicable in obtaining an individual's medical chart or results of diagnostic tests performed as part of an individual's regular medical care that are going to be used for eligibility or as a part of collection of data. There is no timeline on eligibility of tests, labs, and procedures since these are genetic disorders that subjects have had all their lives. EXCLUSION CRITERIA There will be no exclusion from participation in the Lipid Disorder Discovery Pathogenesis protocol on the basis of age/sex/ethnicity/race. Patients with lipid disorder that is likely to result in clinically significant complications (pancreatitis, coronary heart disease) will be evaluated and treated using standard procedures. Subjects will be recruited through direct referrals from primary care providers or academic institutions.