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.

The lipoprotein transport system is vital to the delivery of the hydrophobic fats that are carried in the aqueous environment of the blood. The lipoprotein particles that comprise this system are polydisperse and contain triglycerides, free and esterified cholesterol, phospholipids and proteins. Inborn errors in the lipoprotein transport system lead to alterations in both the steady state concentrations of the various lipoproteins and in the metabolism of these particles. These inborn errors lead to both hyperlipoproteinemia and hypolipoproteinemia. Profound changes in the ambient lipoprotein concentrations have a variety of clinical manifestations. The present study protocol is designed to permit a full plasma evaluation of the lipids, lipoproteins and apolipoproteins, in patients with potential genetic defects in these processes. We will use a variety of research plasma assays. These specialized plasma assays are necessary to correctly diagnose and treat patients that present with the more unusual disorders of lipid metabolism; these patients cannot be diagnosed by standard, CLIA- Certified assays and may require tissue or blood cells for diagnosis and adequate treatment. The study population will include patients which are referred to the Lipid Service, Cardiovascular Branch, NHLBI from private care providers, academic institutions or the NHLBI-MDB website, with any of the following potential lipid abnormalities or clinical stigmata associated with dyslipoproteinemias: a) increased plasma levels of cholesterol, triglycerides, HDL-cholesterol 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.