Lipoprotein(a)

Why This Matters

Lipoprotein(a), or Lp(a), is one of the most important inherited risk factors for atherosclerotic cardiovascular disease. Unlike LDL cholesterol, which is influenced by diet, lifestyle, and many medications, Lp(a) levels are determined predominantly by genetics and remain relatively constant throughout life. Measuring Lp(a) identifies individuals who may carry substantial cardiovascular risk despite having an otherwise acceptable lipid profile.

What Is Lipoprotein(a)?

Lipoprotein(a) is an LDL-like particle in which apolipoprotein(a) is attached to apolipoprotein B-100 by a disulfide bond.

Like LDL, Lp(a) transports cholesterol and contains one ApoB molecule. However, the addition of Apo(a) gives the particle unique biological properties that distinguish it from LDL and contribute to its increased cardiovascular risk.

Plasma Lp(a) concentrations are largely inherited and are determined by variations in the LPA gene.

The Structure of Lp(a)

Lp(a) consists of two major components: an LDL particle containing ApoB-100, and Apo(a), a large glycoprotein that resembles plasminogen, an important protein involved in fibrinolysis (clot breakdown).

The size of Apo(a) varies considerably among individuals because of differences in the number of kringle IV type 2 repeats. In general, smaller Apo(a) isoforms are associated with higher plasma Lp(a) concentrations and greater cardiovascular risk.

How Lp(a) Contributes to Cardiovascular Disease

Lp(a) promotes cardiovascular disease through several mechanisms.

As an ApoB-containing lipoprotein, it can enter and become retained within the arterial wall, contributing to cholesterol accumulation and plaque formation.

Lp(a) also carries large amounts of oxidized phospholipids, which promote vascular inflammation and accelerate atherosclerosis.

In addition, the structural similarity between Apo(a) and plasminogen may interfere with normal fibrinolysis, creating a more prothrombotic environment.

These combined effects make Lp(a) both proatherogenic and potentially prothrombotic.

Lp(a) and Aortic Valve Disease

Elevated Lp(a) is associated not only with coronary artery disease but also with calcific aortic valve stenosis.

Oxidized phospholipids carried by Lp(a) appear to stimulate inflammation and calcification within the aortic valve, accelerating progressive valve narrowing.

This association distinguishes Lp(a) from most other lipoproteins and highlights its broader role in cardiovascular disease.

Measuring Lp(a)

Because Lp(a) concentrations are genetically determined and remain relatively stable throughout life, measurement is usually required only once in adulthood.

Results may be reported in either milligrams per deciliter (mg/dL) or nanomoles per liter (nmol/L). These units are not directly interchangeable because they are influenced by Apo(a) isoform size.

Current guidelines recommend measuring Lp(a) at least once in every adult to identify individuals with inherited elevations that may warrant more aggressive management of other cardiovascular risk factors. Major lipid societies define increased risk as an Lp(a) level at or above approximately 50 mg/dL (roughly 125 nmol/L), though risk rises gradually along a continuum rather than switching on at that line. Elevated Lp(a) is common — population studies estimate that around one in five people worldwide carry a level in the higher-risk range.

Clinical Relevance

Elevated Lp(a) increases the lifetime risk of myocardial infarction, ischemic stroke, peripheral arterial disease, and calcific aortic valve stenosis.

Because conventional lifestyle interventions have little effect on Lp(a), management focuses on aggressively reducing other modifiable cardiovascular risk factors, particularly ApoB-containing lipoproteins.

As of this writing, no drug has been approved anywhere specifically to lower Lp(a) — existing therapies (statins, ezetimibe) leave it largely unchanged, and PCSK9 inhibitors lower it only modestly. Several RNA-based therapies (including pelacarsen, olpasiran, and lepodisiran) have shown they can lower Lp(a) by 80 percent or more in earlier-phase trials, which is a pharmacologic result, not yet a clinical one: the first large outcomes trial designed to show whether lowering Lp(a) this way actually reduces heart attacks and strokes, Lp(a) HORIZON, is expected to report soon. Until an outcomes trial reports positive results, Lp(a) reduction remains a promising but unproven strategy — this is a case where the biological logic is strong (Lp(a) is genetically and causally linked to cardiovascular disease) but the direct treatment evidence is still pending.

Clinical Pearls

• Lp(a) is an inherited ApoB-containing lipoprotein.
• Plasma Lp(a) levels are determined predominantly by genetics.
• Elevated Lp(a) increases the risk of atherosclerotic cardiovascular disease and calcific aortic valve stenosis.
• Lp(a) carries oxidized phospholipids that contribute to vascular inflammation.
• Lp(a) should be measured at least once in every adult.

Common Misconceptions

Misconception: Lp(a) is simply another form of LDL cholesterol.

Reality: Lp(a) is an LDL-like particle with an attached Apo(a) molecule that gives it unique biological properties and additional cardiovascular risk.

Misconception: Diet and exercise substantially lower Lp(a).

Reality: Lifestyle modification has minimal effect on genetically determined Lp(a) concentrations, although it remains essential for reducing overall cardiovascular risk.

Misconception: A normal LDL cholesterol level eliminates the risk associated with elevated Lp(a).

Reality: Individuals with elevated Lp(a) may remain at increased cardiovascular risk despite otherwise acceptable LDL cholesterol levels.

Clinical Bottom Line

Lipoprotein(a) is a genetically determined ApoB-containing lipoprotein that increases the risk of atherosclerotic cardiovascular disease and calcific aortic valve stenosis. Identifying elevated Lp(a) allows clinicians to recognize inherited cardiovascular risk and intensify management of other modifiable risk factors while awaiting the availability of Lp(a)-targeted therapies.