About one person in 500 carries one FH allele
and has an increased risk of heart disease. That means that nearly
500,000 Americans are have one defective allele. Most don't know
it. About one person in a million has two FH alleles; these people
often have heart attacks and die before age 20. Xanthomas (lumps
of fatty tissue) are often a sign of this serious form of FH. People
descended from French Canadians, South African whites, Finns, and
Christian Lebanese often have the two FH alleles. In 1973, Drs.
Michael Brown and Joseph Goldstein and their colleagues at the University
of Texas Southwestern Medical School at Dallas discovered the LDL
receptors in the liver. Then they proved that a lack of LDL receptors
causes a buildup of cholesterol. By purifying the LDL receptor protein,
they isolated the gene responsible for FH in 1984. They received
a Nobel Prize for describing how the gene, the protein, the receptors,
and LDL work in the body's cholesterol system.