Familial Hypercholesterolemia: 1 in 311 People Have It. Most Don't Know.

Familial hypercholesterolemia (FH) is caused by inherited mutations — most often in the LDLR gene, which codes for the LDL receptor responsible for pulling "bad" cholesterol out of your bloodstream. When that receptor doesn't work properly, LDL cholesterol builds up in the blood from childhood onward, not because of diet or lifestyle, but because the cellular machinery meant to clear it is broken from birth. The pooled worldwide prevalence of the more common (heterozygous) form is approximately 1 in 311 people — making it, by some measures, the most common serious monogenic disease in existence. The rarer homozygous form, where a person inherits a mutated copy from both parents, is far more severe and considerably rarer, at roughly 1 in 300,000.

Why "High Cholesterol" Doesn't Capture It

The distinction that matters here is exposure over time, not just the number on a lab report. Someone who develops elevated cholesterol at 55 due to diet has had a few decades of exposure by the time it's caught. Someone with FH has had elevated LDL since birth — meaning by their 20s or 30s, they've already accumulated the kind of arterial plaque buildup a non-FH person might not reach until their 50s or 60s. This is why FH is strongly associated with heart attacks and other cardiovascular events at unusually young ages, sometimes in people who appear otherwise healthy, exercise regularly, and eat reasonably well.

Why Underdiagnosis Is the Real Story

The 2025 study cited above — which used whole genome sequencing across thousands of adult inpatients rather than relying on prior clinical diagnosis — found that only about 1 in 10 people carrying a disease-causing LDLR or APOB variant had ever actually been diagnosed with FH. That's a striking gap for a condition with clear diagnostic criteria and effective treatment. Part of the explanation is structural: routine cholesterol panels flag "high LDL" without distinguishing genetic FH from diet-related elevation, and unless a doctor specifically calculates a validated clinical score (such as the Dutch Lipid Clinic Network criteria) or orders genetic testing, the underlying cause often goes unrecognized — especially in younger patients whose LDL, while abnormally high for their age, may not look alarming in isolation.

Should You Get Tested?

If you have a personal or family history of very high LDL cholesterol, a family history of early heart attacks (before age 55 in men, 65 in women), or physical signs sometimes associated with FH such as cholesterol deposits around the eyes or in tendons, ask your doctor about genetic testing specifically for FH — a standard lipid panel alone won't distinguish it from other causes of high cholesterol. Because FH is caused by well-characterized mutations in a small number of genes, it's also one of the conditions reliably captured by comprehensive genome sequencing, alongside dozens of other cardiovascular risk variants.

For more on inherited disease risk more broadly, see our genome testing and cancer risk guide, and if you're weighing family planning implications of any genetic finding, our advanced family planning guide covers dominant inheritance patterns like FH's in more depth.