# Familial Hypercholesterolemia

Identify probable or definite familial hypercholesterolemia early, confirm etiology when genetic testing will alter family detection or risk assessment, initiate intensive LDL-C lowering, and rapidly distinguish homozygous disease requiring receptor-independent therapy or apheresis from heterozygous disease.

**Clinical question:** How should clinicians diagnose, genetically evaluate, treat, and cascade-screen patients with heterozygous or homozygous familial hypercholesterolemia?

Updated: 2026-09-15T22:48:09.399268+00:00

## What matters in practice
- For probable or definite FH, obtain genetic testing that includes LDLR, APOB, and PCSK9; a pathogenic variant establishes a molecular diagnosis, refines cardiovascular risk, and enables mutation-directed cascade testing. [15][16]
- Treat FH with a maximally tolerated high-intensity statin and target at least a 50% LDL-C reduction from pretreatment values; add ezetimibe and then further LDL-lowering therapy when residual LDL-C or clinical risk remains high. [7][17][18]
- Suspect HoFH when LDL-C is markedly elevated from childhood or ASCVD occurs in childhood; initiate statin plus ezetimibe and rapidly add receptor-dependent or receptor-independent therapy and/or lipoprotein apheresis rather than waiting for clinical ASCVD. [11][19][22]
- PCSK9 inhibitor response in HoFH depends on residual LDL receptor activity; LDLR null/null disease is generally unresponsive, so assess the observed LDL-C response and discontinue ineffective PCSK9 inhibition. [19][22]
- Evinacumab 15 mg/kg intravenously every 4 weeks reduced LDL-C by approximately 47% at 24 weeks in treated HoFH populations, including patients receiving other lipid-lowering drugs or apheresis. [22]
- Cascade testing of first-degree relatives, including children, is a high-yield Tier 1 public-health strategy; use the familial pathogenic variant when available rather than LDL-C alone. [5][8][15]

## Separate likely heterozygous FH from possible homozygous FH at presentation

The urgency of escalation depends on phenotype, age at presentation, and residual LDL receptor function.

Use the untreated or pretreatment LDL-C phenotype, premature ASCVD history, and family pattern to identify patients with clinical FH; formal clinical criteria such as the Dutch Lipid Clinic Network score can support classification. A score above 5 has been used to define possible or definite clinical FH, but a substantial proportion of such patients are mutation-negative by conventional testing, often because of polygenic LDL-C elevation. [9][15]

Escalate immediately to a lipid specialist or experienced FH center when the phenotype suggests HoFH: LDL-C approximately 4 to 10 times normal, severe hypercholesterolemia in childhood, or childhood-onset cardiovascular disease. By comparison, HeFH typically produces LDL-C 2 to 3 times normal and may cause ASCVD from young adulthood. [11]

Do not defer intensive LDL-C lowering while pursuing molecular confirmation. Current FH guidance places maximally tolerated statins and ezetimibe at the base of therapy, with more rapid intensification for established ASCVD, inadequate LDL-C reduction, or a severe phenotype. [17][18]
- Use a documented pretreatment LDL-C whenever possible to judge percentage response to therapy; the practical FH treatment benchmark is at least a 50% LDL-C reduction. [7][18]
- Treat childhood ASCVD, very severe LDL-C elevation, or suspected HoFH as a referral-and-escalation problem rather than as routine primary-prevention hypercholesterolemia. [11][19]

*Phenotypic features that change urgency and therapeutic pathway. [11][19][22]*

| Feature | Likely implication | Immediate next action |
| --- | --- | --- |
| LDL-C 2-3 times normal; ASCVD beginning in young adulthood | Typical HeFH phenotype. [11] | Begin maximally tolerated high-intensity statin; assess need for ezetimibe and further LDL-C lowering. [17][18] |
| LDL-C 4-10 times normal; childhood cardiovascular disease | Possible HoFH with very high short-term cumulative LDL exposure. [11] | Refer promptly to an experienced FH center; begin statin plus ezetimibe and plan early advanced therapy. [19][22] |
| Poor PCSK9 inhibitor response in HoFH | May indicate minimal residual LDLR activity; LDLR null/null disease is generally unresponsive. [19] | Do not continue ineffective receptor-dependent therapy solely by default; consider evinacumab, lomitapide, and/or lipoprotein apheresis. [19][22] |

## Use genetic testing to confirm FH and drive cascade screening

Molecular testing is most useful when the result changes family detection, risk stratification, or diagnostic certainty.

Offer FH genetic testing to patients with definite or probable FH and to at-risk relatives. The recommended core panel includes LDLR, APOB, and PCSK9, with phenotype-directed expansion when appropriate. A pathogenic variant facilitates definitive diagnosis, identifies a group at higher cardiovascular risk, and can improve treatment initiation and adherence. [15][16]

A negative conventional genetic result does not exclude a clinically actionable FH phenotype. Among patients with a Dutch Lipid Clinic score above 5, approximately 60% may be mutation-negative by conventional testing; evidence indicates that many mutation-negative cases reflect accumulation of common LDL-C-raising alleles rather than an undiscovered monogenic cause. Continue phenotype-based LDL-C management rather than withdrawing therapy because testing is negative. [9]

When an index patient has a pathogenic variant, test first-degree relatives for that familial variant and include children. FH cascade testing is classified as a CDC Tier 1 application, and DNA-based cascade testing avoids misclassification caused by overlap in LDL-C distributions between mutation carriers and noncarriers within the same family. [5][8][15]
- Document a three-generation history of premature ASCVD and severe hypercholesterolemia before family outreach; this improves identification of relatives who require expedited lipid measurement and molecular testing. [15][16]
- In mutation-negative clinical FH, screen relatives with lipid testing rather than assuming that variant-based cascade testing will identify all affected relatives. [9]
- Counsel relatives that genetic testing establishes inherited risk when positive but does not replace measurement of LDL-C or assessment for ASCVD risk modifiers. [15][16]

*How genetic results alter management and family testing. [9][15][16]*

| Result in index patient | Interpretation | Family-testing approach |
| --- | --- | --- |
| Pathogenic LDLR, APOB, or PCSK9 variant | Molecularly confirmed monogenic FH; pathogenic variants also identify higher cardiovascular risk. [15][16] | Perform targeted cascade testing of first-degree relatives, including children. [5][8][15] |
| No pathogenic variant on conventional testing | Does not exclude clinically important inherited hypercholesterolemia; polygenic LDL-C elevation is common in this setting. [9] | Use lipid measurements and clinical assessment in relatives; continue phenotype-directed treatment in the index patient. [9] |
| HoFH genotype with absent or severely reduced LDLR activity | Predicts limited efficacy of LDLR-dependent approaches, particularly PCSK9 inhibition in LDLR null/null disease. [19] | Refer to an FH center and prioritize receptor-independent treatment planning. [19][22] |

## Escalate LDL-C lowering in heterozygous FH using response and ASCVD risk

Therapeutic intensity should be judged by achieved LDL-C reduction, residual LDL-C, and presence of ASCVD.

Start a high-intensity statin unless contraindicated or not tolerated, then titrate to the maximum tolerated dose. Statin monotherapy can reduce LDL-C by as much as 55% to 60%, but this is often insufficient for patients with FH and clinically manifest coronary disease. The minimum practical response target is a 50% LDL-C reduction from pretreatment LDL-C. [7][18]

Add ezetimibe when maximal tolerated statin therapy does not produce at least a 50% LDL-C reduction or when residual LDL-C remains unacceptable for the patient's ASCVD risk. Ezetimibe is the usual second-line agent; contemporary FH guidance then incorporates PCSK9 inhibitors and bempedoic acid as additional treatment options when statin-ezetimibe therapy remains inadequate or cannot be fully tolerated. [17][18]

Use clinical risk to determine how quickly to intensify. Prior cardiovascular disease, diabetes, hypertension, smoking, elevated lipoprotein(a), and other risk factors identify patients more likely to need multidrug therapy. Earlier consensus targets cited LDL-C below 100 mg/dL for adults and below 70 mg/dL for adults with known coronary heart disease or diabetes, while emphasizing a percentage reduction of at least 50%. [7]

Consider lipoprotein apheresis for selected patients with severe clinical FH when drug therapy does not achieve adequate LDL-C lowering; contemporary guidance includes apheresis for both heterozygous and homozygous FH. This is a procedure-based escalation with access and treatment-burden tradeoffs, not a substitute for establishing maximally tolerated drug therapy. [17][20]
- At each follow-up, compare LDL-C with the pretreatment value and verify adherence before labeling pharmacologic failure. A less than 50% reduction is a trigger to intensify or reassess tolerability and phenotype. [7][18]
- Refer high-risk patients whose LDL-C remains inadequately controlled after high-intensity statin plus ezetimibe to an experienced lipid specialist for advanced therapy selection. [18]
- Avoid relying on fibrates, bile acid sequestrants, or niacin as routine substitutes for statin-ezetimibe-PCSK9–based intensification in FH because their LDL-C efficacy is comparatively limited. [18]

*Response-based treatment sequence for heterozygous FH. [7][17][18]*

| Treatment stage | Use when | Decision checkpoint |
| --- | --- | --- |
| Maximally tolerated high-intensity statin | Initial pharmacotherapy for FH. [1][17][18] | Aim for at least 50% LDL-C reduction from pretreatment. [7][18] |
| Add ezetimibe | LDL-C reduction is less than 50% or residual risk remains high on statin therapy. [18] | Reassess LDL-C response and adherence before next escalation. [18] |
| Add PCSK9 inhibitor or bempedoic acid | Inadequate response or inability to achieve sufficient LDL-C lowering with statin plus ezetimibe. [17] | Use achieved LDL-C, ASCVD status, tolerability, access, and patient preference to choose therapy. [17] |
| Lipoprotein apheresis | Selected severe HeFH with inadequate pharmacologic control. [17][20] | Continue intensive drug therapy and reassess procedure burden versus LDL-C response. [20] |

## Treat homozygous FH with early multidrug and receptor-independent escalation

HoFH usually requires advanced treatment shortly after diagnosis because statin-based therapy alone is rarely sufficient.

Initiate maximally tolerated statin plus ezetimibe in HoFH, but anticipate inadequate LDL-C lowering because both therapies depend substantially on residual LDL receptor activity. Advanced treatment should begin with or shortly after statin-ezetimibe therapy, rather than being delayed until symptoms or clinical ASCVD develop. [19][22]

A PCSK9 monoclonal antibody is commonly an initial add-on in HoFH and produces an average LDL-C reduction of about 25% in reported studies; response is variable and depends on residual LDLR expression. In LDLR null/null disease, PCSK9 inhibitors are generally completely ineffective. Measure the LDL-C response after addition and discontinue the agent if it does not significantly lower LDL-C. [19][22]

For receptor-independent LDL-C lowering, use therapies reserved for HoFH. Lomitapide and evinacumab are FDA-approved for HoFH; lomitapide is an oral microsomal triglyceride transfer protein inhibitor, whereas evinacumab inhibits angiopoietin-like protein 3. Lomitapide carries a boxed warning for hepatotoxicity, including aminotransferase elevations and hepatic steatosis that may progress to cirrhosis. [20][24]

Evinacumab is administered intravenously at 15 mg/kg every 4 weeks. In a placebo-controlled HoFH trial with mean baseline LDL-C approximately 250 to 260 mg/dL despite extensive background therapy, evinacumab produced a 47% LDL-C reduction at 24 weeks versus a 1.9% LDL-C increase with placebo; lowering appeared after 2 weeks and was observed regardless of concomitant therapy, apheresis use, or LDLR genotype. [22]

Use lipoprotein apheresis as an effective advanced option in HoFH, particularly when pharmacologic response is inadequate or access to receptor-independent drugs is limited. If apheresis is the only available add-on after poor first-line response, do not delay initiation until cardiovascular symptoms occur. [19][20]
- Assess LDLR genotype and actual LDL-C response when available; these guide whether receptor-dependent PCSK9 inhibition should be continued. [19][22]
- Monitor aminotransferases and hepatic toxicity carefully in patients receiving lomitapide because of its boxed hepatotoxicity warning. [24]
- Select among evinacumab, lomitapide, PCSK9 inhibition, and apheresis according to residual LDLR activity, LDL-C response, tolerability, access, cost, and procedural burden. [19][20][22]

*Advanced therapy selection in homozygous FH. [19][20][22][24]*

| Option | Expected role | Key selection or monitoring point |
| --- | --- | --- |
| PCSK9 monoclonal antibody | Common first advanced add-on; average LDL-C reduction around 25% in HoFH studies. [19] | Requires residual LDLR activity; null/null disease is generally unresponsive. Stop if no meaningful LDL-C reduction. [19][22] |
| Evinacumab 15 mg/kg IV every 4 weeks | Receptor-independent add-on for HoFH. [22][24] | Reduced LDL-C by 47% at 24 weeks in a pivotal HoFH trial despite intensive background treatment. [22] |
| Lomitapide | Oral receptor-independent treatment reserved for HoFH. [20][24] | Monitor for aminotransferase elevation and hepatic steatosis/cirrhosis risk. [24] |
| Lipoprotein apheresis | Effective option for severe HoFH and selected HeFH. [17][20] | Start without waiting for CVD symptoms when needed after inadequate first-line response. [19] |

## Plan pediatric detection and pregnancy management before treatment interruption becomes urgent

Children in affected families and patients planning pregnancy require proactive therapy and testing decisions.

Test first-degree relatives of an index case, including children, through cascade screening. Pediatric FH screening remains controversial in the United States because long-term trials linking childhood statin treatment to events decades later are limited, but the American Academy of Pediatrics has endorsed multisociety pediatric cholesterol-screening guidance and FH is a Tier 1 cascade-testing condition. [8]

Available pediatric approvals include pravastatin and rosuvastatin from age 8 years, simvastatin from age 10 years, ezetimibe for patients older than 10 years, evolocumab from age 10 years for FH, evinacumab from age 5 years for HoFH, and lomitapide from age 18 years for HoFH. Use age-approved therapy in consultation with a pediatric lipid specialist for severe phenotypes. [24]

Address pregnancy planning before conception in every patient receiving systemic LDL-lowering therapy. Statins should be discontinued before conception and are contraindicated during pregnancy in the cited clinical literature. For severe FH, particularly HoFH or established ASCVD, bile acid sequestrants are the pharmacologic option generally regarded as safest because they are not systemically absorbed, although they can reduce absorption of fat-soluble vitamins; consider LDL apheresis when cardiovascular risk is very high. [13][21]

Avoid ezetimibe, PCSK9 inhibitors, lomitapide, and bempedoic acid during pregnancy because sufficient pregnancy safety data are lacking. Reassess LDL-C therapy after pregnancy and breastfeeding decisions with an FH specialist, especially in patients with HoFH or prior ASCVD. [21]
- For a child with a known familial pathogenic variant, prioritize targeted genetic cascade testing rather than waiting for adult lipid screening. [5][8][15]
- For a patient with HoFH contemplating pregnancy, coordinate lipidology, maternal-fetal medicine, and apheresis services before stopping systemic LDL-lowering agents. [13][21]

*Selected age and pregnancy considerations in FH. [13][21][24]*

| Situation | Action | Important limitation |
| --- | --- | --- |
| Child in an FH family | Perform cascade screening, including targeted testing when the familial pathogenic variant is known. [5][8][15] | Screening policy controversies do not negate the Tier 1 rationale for family-based detection. [8] |
| Pediatric HoFH | Consider age-approved evinacumab from age 5 years; lomitapide is approved from age 18 years. [24] | Manage severe pediatric disease with a pediatric lipid specialist. [11][24] |
| Pregnancy or conception planning | Stop statins before conception; use lifestyle measures, consider bile acid sequestrants, and consider LDL apheresis for very high-risk severe FH. [13][21] | Bile acid sequestrants may impair fat-soluble vitamin absorption; monitor accordingly. [21] |

## References
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## Editorial note

Prepared from cited clinical literature using Astra's research workflow. Verify recommendations against current guidance and patient-specific factors.