For a very small number of people, high cholesterol levels, especially LDL cholesterol levels, are due to genetic problems with their LDL receptors — the place where LDL cholesterol enters the blood cell. This is called familial hypercholesterolemia (FH). There are two types, heterozygous FH (in which one receptor on the blood cell has mutated) and homozygous (the blood cells have two mutated receptors). In heterozygous FH, LDL cholesterol levels can run as high as 350-500 mg/dL. In homozygous FH, which is much more rare, LDL cholesterol levels can reach as high as 700-1,200 mg/dL. People with either type of FH are at an increased risk for premature coronary heart disease (CHD). For those with a parent or a sibling who has been diagnosed with FH or early CHD, cholesterol levels should be tested early — even in childhood. LDL-lowering drugs are usually required by early adulthood. Return to previous page.