Inherited Cholesterol Marker (Lp(a)) and Your Genetics
Written by Scott Peeples, BS Biomedical Sciences · ExomeDNA Founder
Research base: Moderate.
What is Lp(a) and why does the LPA gene matter?
Lipoprotein(a) [Lp(a)] is a modified low-density lipoprotein particle distinguished by the presence of apolipoprotein(a) [apo(a)], covalently linked to apolipoprotein B-100 via a disulfide bond. Elevated plasma Lp(a) is a causally established, independent risk factor for atherosclerotic cardiovascular disease, myocardial infarction, stroke, and aortic valve stenosis. It is one of the most prevalent inherited cardiovascular risk factors, with elevated levels (above 50 mg/dL or ~125 nmol/L) present in approximately 20% of the global population.
The defining and primary genetic determinant of Lp(a) levels is the LPA gene on chromosome 6q — the gene encoding apo(a). LPA is unusual among lipoprotein genes because its protein product is unique to humans (and some non-human primates) and its population-level copy number polymorphism (the number of KIV-2 kringle repeats) is the single most important determinant of circulating Lp(a) concentration. This early GWAS dataset focuses on the LPA locus and its immediate genomic neighborhood.
The genetics behind Lp(a) levels at the LPA locus
The LPA gene sits within a genomic region on 6q26-27 that also contains the structurally and evolutionarily related gene PLG (plasminogen) and LPAL2 (a pseudogene-like copy of LPA). This chromosomal neighborhood reflects the evolutionary origin of Lp(a): the LPA gene arose by tandem duplication of PLG after the divergence of humans from lower mammals, explaining why apo(a) has extensive structural homology to plasminogen.
LPA (Lipoprotein(a)), ranked first (locus-to-gene score 0.771, high confidence), encodes apolipoprotein(a), the unique protein component that defines Lp(a) particles. The LPA gene contains a variable number of KIV-2 tandem kringle domain repeats — from roughly 2 to more than 40 copies depending on the allele. Individuals inheriting shorter LPA alleles (fewer KIV-2 repeats) tend to have higher Lp(a) plasma levels, because smaller apo(a) isoforms are more efficiently secreted by the liver. This inverse relationship between LPA allele size and Lp(a) levels is one of the clearest examples of copy number variation directly determining a quantitative plasma trait.
PLG (Plasminogen), ranked second (locus-to-gene score 0.308, low confidence), encodes the zymogen that is converted to plasmin — the primary fibrinolytic enzyme in blood. PLG and LPA are structurally homologous, sharing kringle domain architecture. Lp(a)'s resemblance to plasminogen has direct functional consequences: apo(a) can competitively inhibit plasminogen binding to fibrin, potentially impairing clot dissolution and contributing to the thrombotic component of Lp(a)'s cardiovascular risk. The genetic association of PLG with Lp(a) levels in these early GWAS may reflect both its proximity to LPA on chromosome 6q and genuine functional interactions between the two protein systems.
LPAL2 (Lipoprotein(a)-like 2) is a pseudogene in the 6q26 region with strong sequence similarity to LPA. LPAL2 does not produce functional apo(a) protein, but its genomic presence creates complex linkage disequilibrium patterns in this region that influence which variants tag the true LPA functional alleles in GWAS studies.
SLC22A2 and SLC22A3 (Solute Carrier Family 22 Members 2 and 3) are organic cation transporters. Their association with Lp(a) levels in this genomic region may reflect their chromosomal proximity to the LPA/PLG locus rather than a direct functional role in lipoprotein metabolism, though they could theoretically influence renal handling of Lp(a) metabolites.
What the research says
The two studies underlying this trait's evidence represent the early genome-wide era of Lp(a) genetics, establishing the primacy of the 6q locus.
Ober C et al. (2009) — Journal of Lipid Research — PMID 19124843
"Genome-wide association study of plasma lipoprotein(a) levels identifies multiple genes on chromosome 6q." One of the first GWAS to formally identify chromosome 6q — the LPA/PLG region — as the dominant genomic locus for plasma Lp(a) concentration. This study established the genomic architecture of Lp(a) genetics and confirmed that the signal originates from within and near the LPA gene itself.
Qi Q et al. (2012) — European Heart Journal — PMID 21900290
"Genetic variants, plasma lipoprotein(a) levels, and risk of cardiovascular morbidity and mortality among two prospective cohorts of type 2 diabetes." A prospective study linking Lp(a) genetic variants to hard cardiovascular endpoints in diabetic cohorts — providing the critical step from genetic association to clinical consequence and establishing Lp(a) as a cardiovascular risk marker independent of other lipid measures in high-risk populations.
The moderate confidence tier reflects the age of these two foundational studies (2009, 2012) relative to the much larger Lp(a) GWAS literature that has since emerged. The biology is well-established — LPA is unambiguously the primary genetic determinant of Lp(a) levels — but the gene set here (5 filtered genes) is narrower than what later, larger studies have identified. The LPA locus findings from these studies have been replicated many times since.
How Lp(a) levels affect you
Lp(a) is a genuinely causal cardiovascular risk factor supported by Mendelian randomization evidence: genetic variants that raise Lp(a) also raise cardiovascular risk, confirming that the association is not driven by confounding. One in five people globally has Lp(a) above the threshold associated with materially increased cardiovascular risk. Because Lp(a) is largely refractory to statins and lifestyle modification, it represents residual cardiovascular risk even in patients receiving standard lipid-lowering therapy.
The thrombotic mechanism (plasminogen competition), the inflammatory mechanism (oxidized phospholipid carriage), and the cholesterol delivery mechanism all operate simultaneously — making Lp(a) a multidimensional risk factor rather than simply a high-LDL equivalent.
Working with your variant profile
For clinical cardiovascular risk assessment, direct plasma Lp(a) measurement is far more informative than genetic variant data for this trait. Lp(a) measurement is widely available as a standard lipid panel add-on, is not subject to fasting requirements, and is covered by major cardiology guidelines as a recommended one-time lifetime screen for adults. If the ExomeDNA variant profile flags associations with Lp(a) genetics, the most actionable next step is measuring plasma Lp(a) directly.
RNA-based therapeutics specifically targeting LPA mRNA (including pelacarsen, olpasiran, and lepodisiran) are in Phase 3 clinical development and achieve dramatic Lp(a) reductions. These treatments, if approved, would represent the first direct pharmacological approach to the LPA gene's product for cardiovascular risk reduction.
Related traits and genes
Lp(a) levels are closely related to coronary artery disease, aortic valve stenosis, ischemic stroke, and cardiovascular mortality. The LPA gene's structural relationship to PLG connects Lp(a) biology to fibrinolysis and thrombosis genetics. A separate ExomeDNA trait entry covers the broader polygenic architecture of lipoprotein(a) levels across 94 candidate genes including APOE, PCSK9, and CETP — the secondary genetic contributors that operate beyond the primary LPA locus.
Frequently asked questions
What makes the LPA gene so unusual compared to other lipid genes?
LPA is unique in several ways: it is present only in humans and some non-human primates, having evolved by duplication of PLG after divergence from other mammals. Its protein product apo(a) is covalently linked to apoB-100 on the Lp(a) particle — unlike most apolipoproteins, which associate non-covalently. Most importantly, the variable number of KIV-2 kringle repeats in the LPA gene directly determines Lp(a) levels: shorter alleles produce smaller, more hepatically-secreted apo(a) isoforms and higher Lp(a) concentrations.
Why does Lp(a) interfere with fibrinolysis?
Apo(a), the distinguishing component of Lp(a), shares structural homology with plasminogen — specifically its kringle domain architecture. Because kringle IV and V domains of apo(a) resemble those of plasminogen, apo(a) can compete with plasminogen for fibrin binding sites on forming blood clots. This competitive inhibition of plasminogen binding reduces the efficiency of plasmin-mediated clot dissolution, contributing to Lp(a)'s pro-thrombotic cardiovascular risk beyond its cholesterol-carrying properties.
Why can Lp(a) levels not be lowered by statins?
Statins work by inhibiting HMG-CoA reductase, reducing cholesterol synthesis and upregulating hepatic LDL receptor expression. LDL receptors mediate LDL clearance very efficiently, but their role in Lp(a) clearance is limited because apo(a) structurally occludes some of the receptor-binding regions of the apoB-100 on Lp(a) particles. As a result, statin-driven LDL receptor upregulation has minimal effect on Lp(a) levels — and in some individuals, statins mildly raise Lp(a), possibly through compensatory LPA transcription changes.
What is LPAL2 and does it produce Lp(a)?
LPAL2 (Lipoprotein(a)-like 2) is a paralogous gene in the 6q26 region that resembles LPA in sequence but does not produce a functional apo(a) protein. It lacks the key structural features required for apo(a) secretion and Lp(a) particle assembly. Its genomic presence creates complex linkage disequilibrium with LPA that complicates fine-mapping of the causal variants driving Lp(a) level variation in GWAS analyses.
How is the LPA KIV-2 repeat number measured clinically?
The KIV-2 copy number variation in LPA is not reliably captured by standard SNP arrays or exome sequencing. Clinical measurement of Lp(a) levels via plasma assay (immunonephelometry or immunoturbidimetry, ideally reported in nmol/L) is the standard method and is unaffected by this sequencing limitation. Direct isoform sizing by gel electrophoresis or long-read sequencing can determine KIV-2 repeat number in research settings, but is not routine clinically.