familial dysbetalipoproteinemia

an inherited disorder of lipoprotein metabolism caused by mutations in the APOE gene (locus: 19q13.2), which encodes apolipoprotein E (apo E), that result in defective binding of apo E to lipoprotein receptors. It is characterized biochemically by accumulation of β-VLDL (chylomicron remnants and very-low-density lipoprotein remnants) enriched in mutant apo E, with equally elevated cholesterol and triglycerides; the phenotype is that of a type III hyperlipoproteinemia. Clinical manifestations include tuberous or planar xanthomas, particularly of the palmar crease (xanthoma striatum palmare), and premature coronary and peripheral atherosclerosis. The term is sometimes used for all patients with this mutant apo E, although the majority are normolipidemic and clinically normal. Inheritance is usually autosomal recessive, requiring interaction between the mutant apo E and genetic or environmental factors to cause hypertriglyceridemia, but rare autosomal dominant mutations occur. Called also broad beta or floating beta disease.