Composition of low-density lipoprotein in children with hyperlipoproteinaemia.

Low-density lipoprotein composition, studied in 7 pre-pubertal children with secondary hyperlipoproteinaemia, did not differ significantly from that found in 12 normal children. This contrasts with the findings in 12 children with the heterozygous form of familial hypercholesterolaemia in whom the low-density lipoprotein was significantly deficient in triglyceride (p smaller than 0.001) and protein (p smaller than 0.025), and had an increased proportion of cholesterol esters compared with normal (p greater than 0.01). Treatment which lowered serum cholesterol and low-density lipoprotein concentration in these children did not materially alter the abnormalities of composition of the low-density lipoprotein. The data support the hypothesis that an abnormality of composition of low-density lipoprotein is an integral feature of familial hypercholesterolaemia and does not simply result from an increased concentration of low-density lipoprotein of whatever cause.