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An inherited risk
Between 8% and 12% of people have enough Lp(a) for it to contribute to atherosclerosis, and one estimate puts it as high as 20%. Because it is genetically determined, it is something people are born with and only need checked once, including in a 20-year-old, where it can contribute to the early atherosclerosis seen in young people.
The lipoprotein families
Lipoproteins come in two families. Those wrapped in ApoA proteins make up the HDL family, and those wrapped in ApoB make up the VLDL, IDL, and LDL family. Lp(a) is an LDL particle carrying a further protein, apolipoprotein little a, and in 10% to 20% of the population it is a really bad actor.
Its concentration is so small compared with other particles that it generally doesn't show up much in ApoB, the count of particles that drives atherosclerosis.
Why is Lp(a) mostly set by genes?
Lp(a) levels are controlled mainly by the LPA gene, which varies in the number of repeats of a segment called kringle IV type 2. Fewer repeats produce a smaller version of the protein that the liver secretes faster, so levels are higher. A 1992 study by Eric Boerwinkle and colleagues in the Journal of Clinical Investigation found that variation at the LPA gene accounts for more than 90 percent of the differences in Lp(a) concentration between people.
Why is Lp(a) so harmful to arteries?
Lp(a) is the main carrier of oxidized phospholipids in the blood, which provoke inflammation in the artery wall. Its apolipoprotein(a) piece also resembles plasminogen, the protein that dissolves clots, which led researchers to propose that it interferes with clot breakdown. The Emerging Risk Factors Collaboration reported in JAMA in 2009 a continuous link between Lp(a) concentration and coronary risk.
How was Lp(a) discovered?
The Norwegian geneticist Kåre Berg described Lp(a) in 1963 while studying inherited variation in blood antigens. He found a variant of the LDL fraction that behaved like an inherited trait and named it Lp(a). Berg later showed that its concentration is passed down in families.
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