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an excess of lipoproteins in the blood, due to a disorder of lipoprotein metabolism; it may be acquired or hereditary. The acquired form occurs secondary to another disorder or as a result of environmental factors such as diet. The hereditary form is classified into five major phenotypes based on clinical features, enzymatic abnormalities, and serum lipoprotein electrophoretic patterns: Type I may be manifested clinically by repeated bouts of abdominal pain and vomiting, recurrent acute pancreatitis, eruptive xanthomas, hepatosplenomegaly, and lipemia retinalis. Type II (called also familial hypercholesterolemia) is an autosomal dominant condition characterized by tendinous and tuberous xanthomas, xanthelasmas, early onset of corneal arcus, and accelerated atherosclerosis; children homozygous for the defect may have coronary artery disease and myocardial infarctions in childhood. Type III is characterized chiefly by planar xanthomas and is related to familial dysbetalipoproteinemia. Type IV is marked by mild hypertriglyceridemia and is related to tangier disease and is marked by increased incidence of vascular disease, abnormal glucose tolerance, and family history of diabetes mellitus. Type V is characterized by severe hypertriglyceridemia and may include diabetes mellitus, eruptive xanthomas, and recurrent acute pancreatitis.