Serum lipid and apolipoprotein A and B levels in familial hypercholesterolemia.

Serum lipid and apolipoprotein A (apo A) and B (apo B) levels were studied in a family with familial hypercholesterolemia (FH), which comprised two heterozygous parents, five heterozygous children, one homozygote and one normal child. Lipid levels were compared with those of age- and sex-matched normal controls. All subjects with FH had total serum cholesterol and low density lipoprotein-cholesterol (LDL-C) levels greater than the 90th percentile value for the reference range. High density lipoprotein-cholesterol (HDL-C) levels were less than the corresponding 13th percentile in heterozygous subjects. The homozygous child had grossly elevated levels of LDL-C and apo B, and very low levels of HDL-C and apo A. The most powerful discriminating variable between normal, heterozygous and homozygous family members was the LDL-C/HDL-C ratio.