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A genetic variant in the gene for your body's main cholesterol clearing receptor that causes dangerously high LDL cholesterol from birth.
If you carry this variant, your body has been struggling to clear cholesterol from your blood since the day you were born. The LDLR c.2096C>T variant (also called Pro699Leu) is a change in the gene that builds your LDL receptor, the protein on the surface of your cells responsible for pulling LDL cholesterol out of your bloodstream. When this receptor does not work properly, LDL cholesterol accumulates in your blood year after year, silently accelerating the process that leads to heart attacks and strokes.
This variant causes a condition called familial hypercholesterolemia, or FH. Unlike high cholesterol driven by diet or lifestyle, FH is inherited and present from birth. Knowing whether you carry this variant tells you something no standard cholesterol panel can: whether your high LDL is a lifelong genetic condition requiring early, aggressive treatment rather than a problem you can manage with diet alone.
The clinical stakes are significant. Carriers of pathogenic LDLR mutations like this one face roughly 3.6 times the risk of coronary artery disease compared to non-carriers (95% CI: 3.24 to 4.08). That elevated risk is not something that develops in middle age. It has been accumulating since childhood.
Your LDL receptor works like a recycling system. It sits on the surface of your cells (especially liver cells), grabs LDL particles from the blood, pulls them inside the cell for disposal, then returns to the surface to repeat the process. One critical step in this cycle is the moment the receptor releases the LDL particle after pulling it inside. That release depends on a specific structural region of the receptor called the beta-propeller domain.
The Pro699Leu variant changes a single building block in this beta-propeller domain, swapping a proline for a leucine at position 699. This swap disrupts the receptor's ability to fold correctly and reach the cell surface. Laboratory studies in cells lacking normal LDL receptors show that this variant leads to reduced receptor presence on the cell surface and decreased ability to pull LDL particles inside.
The result is straightforward: fewer working receptors on your cells means less LDL gets cleared from your blood, and your cholesterol climbs.
Your result will show one of three genotypes. How severely your cholesterol is affected depends on whether you inherited one copy or two copies of the variant.
C/C (no copies of the variant): Your LDL receptors function normally. You have standard cholesterol clearance and no elevated genetic risk from this variant.
C/T (one copy, heterozygous): You have heterozygous familial hypercholesterolemia. About half of your LDL receptors are impaired. Untreated LDL cholesterol levels typically range from 190 to 400 mg/dL in adults and 160 to 400 mg/dL in children. Because this variant causes severe receptor impairment, your levels may trend toward the higher end of that range.
Without treatment, men with heterozygous FH face a 50% risk of a fatal or nonfatal coronary event by age 50. For women, that risk reaches 30% by age 60. These events often occur 10 to 20 years earlier than they would in the general population.
T/T (two copies, homozygous): You have homozygous familial hypercholesterolemia, an extremely rare and severe condition. With minimal to no working LDL receptors, untreated LDL cholesterol typically exceeds 500 mg/dL and can surpass 1000 mg/dL. Cardiovascular disease can develop in childhood or adolescence. Physical signs such as tendon xanthomas (cholesterol deposits in the tendons) and aortic valve disease may appear before age 10.
If you are heterozygous (C/T), each of your children has a 50% chance of inheriting the variant. This makes cascade screening of your first-degree relatives, meaning your parents, siblings, and children, essential. Early identification in family members can be lifesaving.
Among the hundreds of known LDLR mutations, some completely eliminate receptor function (called "null" variants) while others leave the receptor partially working (called "defective" variants). This distinction matters for your prognosis. Based on functional studies showing reduced cell surface expression and impaired LDL uptake, Pro699Leu likely behaves as a defective variant rather than a null one.
That distinction has real consequences. In heterozygous carriers, null mutations confer roughly twice the risk of major cardiovascular events compared to defective mutations, independent of traditional risk factors. In homozygous individuals, those with two null mutations have higher LDL cholesterol than those with a mix of null and defective variants, who in turn have higher levels than those with two defective variants.
What this means for you: if you carry Pro699Leu, the fact that it is likely defective rather than null is relatively favorable within the spectrum of FH mutations, but it still requires serious, sustained treatment.
Because this is a genetic variant, your genotype itself does not change. But the LDL cholesterol level it produces can be substantially lowered with the right interventions. Treatment is typically layered, starting with the most accessible options and escalating based on your response.
Statins: Atorvastati or rosuvastatin combined with ezetimibe is the standard first-line approach for heterozygous carriers. However, reaching aggressive LDL targets with medications alone is difficult in FH. Only 1.3% of heterozygous FH individuals reach LDL cholesterol below 70 mg/dL on single-drug therapy. This is why combination therapy is almost always necessary.
PCSK9 inhibitors: Evolocumab, alirocumab, and inclisiran provide an additional 50 to 60% LDL cholesterol reduction. These drugs work by increasing the number of LDL receptors on your cell surfaces. They are particularly effective in heterozygous carriers because you still have one working copy of the gene producing functional receptors that can be upregulated.
Bempedoic acid: This oral medication provides roughly 21% additional LDL cholesterol reduction when added to statins, though the effect is smaller in those already taking statins. It offers an alternative for those who cannot tolerate higher statin doses.
Therapies for homozygous or severe cases: If you have two copies of the variant (T/T), your receptors are too impaired for receptor-dependent drugs to work well on their own. Treatments that bypass the LDL receptor entirely may be necessary. These include lomitapide (which blocks fat-carrying particle assembly in the liver), evinacumab (which targets a protein called angiopoietin-like 3), and LDL apheresis (a procedure that physically filters LDL from your blood).
Diet and lifestyle: A heart-healthy diet low in saturated fat, regular exercise, smoking cessation, and weight management are foundational. But they are not sufficient on their own to control LDL cholesterol in FH. Think of lifestyle measures as the floor of your treatment plan, not the ceiling.