Familial hypercholesterolemia in children and the importance of early treatment

PURPOSE OF REVIEW

Familial hypercholesterolemia leads to elevated levels of low-density lipoprotein cholesterol (LDL-C) from birth onwards due to a pathogenetic variation in genes in cholesterol metabolism. Early screening to identify and subsequently treat children with familial hypercholesterolemia is crucial to reduce the risk of premature atherosclerotic cardiovascular disease (ASCVD). This review focuses on recent insights in the field of pediatric familial hypercholesterolemia.

RECENT FINDINGS

Screening in childhood and early initiation of optimal lipid-lowering therapy (LLT) have shown promising outcomes in the prevention of ASCVD. In addition, cost-effectiveness research has demonstrated highly favorable results. With the availability of novel therapies, familial hypercholesterolemia has become a well treatable disease.

SUMMARY

Children with familial hypercholesterolemia benefit from early detection and optimal treatment of their elevated LDL-C levels.

Lipid metabolism during pregnancy: consequences for mother and child

PURPOSE OF REVIEW

Accommodating fetal growth and development, women undergo multiple physiological changes during pregnancy. In recent years, several studies contributed to the accumulating evidence about the impact of gestational hyperlipidemia on cardiovascular risk for mother and child. This review aims to provide a comprehensive overview of the current research on lipid profile alterations during pregnancy and its associated (cardiovascular) outcomes for mother and child from a clinical perspective.

RECENT FINDINGS

In a normal pregnancy, total and LDL-cholesterol levels increase by approximately 30-50%, HDL-cholesterol by 20-40%, and triglycerides by 50-100%. In some women, for example, with familial hypercholesterolemia (FH), a more atherogenic lipid profile is observed. Dyslipidemia during pregnancy is found to be associated with adverse (cardiovascular) outcomes for the mother (e.g. preeclampsia, gestational diabetes, metabolic syndrome, unfavorable lipid profile) and for the child (e.g. preterm birth, large for gestational age, preatherosclerotic lesions, unfavorable lipid profile).

SUMMARY

The lipid profile of women during pregnancy provides a unique window of opportunity into the potential future cardiovascular risk for mother and child. Better knowledge about adverse outcomes and specific risk groups could lead to better risk assessment and earlier cardiovascular prevention. Future research should investigate implementation of gestational screening possibilities.

Current and emerging monoclonal antibodies for treating familial hypercholesterolemia in children

INTRODUCTION

Heterozygous familial hypercholesterolemia (HeFH) is a common genetic disorder caused by pathogenic variants in the LDL-C metabolism. Lifelong exposure to elevated LDL-C levels leads to a high risk of premature cardiovascular disease. To reduce that risk, children with HeFH should be identified and treated with lipid-lowering therapy. The cornerstone consists of statins and ezetimibe, but not in all patients this lowers the LDL-C levels to treatment targets. For these patients, more intensive lipid-lowering therapy is needed.

AREAS COVERED

In this review, we provide an overview of the monoclonal antibodies which are currently available or being tested for treating HeFH in childhood.

EXPERT OPINION

Monoclonal antibodies that inhibit PCSK9 are first in line lipid-lowering treatment options if oral statin and ezetimibe therapy are insufficient, due to intolerance or very high baseline LDL-C levels. Both evolocumab and alirocumab have been shown to be safe and effective in children with HeFH. For children, evolocumab has been registered from the age of 10 years old and alirocumab from the age of 8 years old. The costs of these new agents are much higher than oral therapy, which makes it important to only use them in a selected patient population.

Clinical practice recommendations on lipoprotein apheresis for children with homozygous familial hypercholesterolaemia: An expert consensus statement from ERKNet and ESPN

Homozygous familial hypercholesterolaemia is a life-threatening genetic condition, which causes extremely elevated LDL-C levels and atherosclerotic cardiovascular disease very early in life. It is vital to start effective lipid-lowering treatment from diagnosis onwards. Even with dietary and current multimodal pharmaceutical lipid-lowering therapies, LDL-C treatment goals cannot be achieved in many children. Lipoprotein apheresis is an extracorporeal lipid-lowering treatment, which is used for decades, lowering serum LDL-C levels by more than 70% directly after the treatment. Data on the use of lipoprotein apheresis in children with homozygous familial hypercholesterolaemia mainly consists of case-reports and case-series, precluding strong evidence-based guidelines. We present a consensus statement on lipoprotein apheresis in children based on the current available evidence and opinions from experts in lipoprotein apheresis from over the world. It comprises practical statements regarding the indication, methods, treatment goals and follow-up of lipoprotein apheresis in children with homozygous familial hypercholesterolaemia and on the role of lipoprotein(a) and liver transplantation.

CTCA in children with severe heterozygous familial hypercholesterolaemia: Screening for subclinical atherosclerosis

Familial hypercholesterolemia (FH) is one of the most common genetically inherited disorders in the world. Children with severe heterozygous FH (HeFH), i.e. untreated low-density lipoprotein cholesterol (LDL-C) levels above the 90th percentile for age and sex among FH mutation carriers, can have LDL-C levels that overlap levels of children with homozygous FH (HoFH), but treatment regimen and cardiovascular follow-up to prevent cardiovascular disease are less intensive in children with severe HeFH. In children with HoFH, subclinical atherosclerosis can already be present using computed tomography coronary angiography (CTCA). The question remains whether this is also the case in children with severe HeFH who have a high exposure to elevated LDL-C levels from birth onwards as well. We calculated the cumulative LDL-C exposure (CEtotal [mmol]) in four children with severe HeFH and performed computed tomography coronary angiography (CTCA). These children, aged 13, 14, 15 and 18 years, had CEtotal of 71.3, 97.8, 103.6 and 136.1 mmol, respectively. None of them showed abnormalities on cardiovascular imaging, despite high LDL-C exposure. The results of this study, do not give us an indication to recommend performing CTCA routinely in children with severe HeFH.

Clinical practice recommendations on lipoprotein apheresis for children with homozygous familial hypercholesterolemia: an expert consensus statement from ERKNet and ESPN

Homozygous familial hypercholesterolaemia is a life-threatening genetic condition, which causes extremely elevated LDL-C levels and atherosclerotic cardiovascular disease very early in life. It is vital to start effective lipid-lowering treatment from diagnosis onwards. Even with dietary and current multimodal pharmaceutical lipid-lowering therapies, LDL-C treatment goals cannot be achieved in many children. Lipoprotein apheresis is an extracorporeal lipid-lowering treatment, which is well established since three decades, lowering serum LDL-C levels by more than 70% per session. Data on the use of lipoprotein apheresis in children with homozygous familial hypercholesterolaemia mainly consists of case-reports and case-series, precluding strong evidence-based guidelines. We present a consensus statement on lipoprotein apheresis in children based on the current available evidence and opinions from experts in lipoprotein apheresis from over the world. It comprises practical statements regarding the indication, methods, treatment targets and follow-up of lipoprotein apheresis in children with homozygous familial hypercholesterolaemia and on the role of lipoprotein(a) and liver transplantation.

Advances in familial hypercholesterolaemia in children

Familial hypercholesterolaemia is a common, dominantly inherited disease that results in high concentrations of low-density lipoprotein cholesterol and in premature cardiovascular disease. To prevent cardiovascular disease and premature mortality, patients with the condition need to be identified and to start treatment early in life. In this Review, we discuss the treatment of heterozygous and homozygous familial hypercholesterolaemia in children, including lifestyle modifications, current pharmacological treatment options, and promising novel lipid-lowering treatments. In particular, these new therapies are expected to improve outcomes for patients with severe heterozygous familial hypercholesterolaemia or statin intolerance. For patients with homozygous familial hypercholesterolaemia, lipoprotein apheresis is currently the most valuable therapy available, but new approaches might reduce the need for this effective yet invasive, time-consuming, and expensive treatment.

[Detection and treatment of familial hypercholesterolaemia; the earlier, the better?]

A recent Dutch study in patients with familial hypercholesterolaemia (FH), suggests that long-term statin treatment initiated at childhood reduces the risk for cardiovascular events in adulthood. None of the patients developed rhabdomyolysis or other serious adverse effects. Early detection of FH is crucial for early treatment initiation. However, the Dutch cascade screening program ended at the end of 2013, at which point approximately 40,000 FH patients had not yet been identified. In order to trace this cohort, in 2014 the 'LEEFH' foundation (National Expertise Centre for Genetic Testing for Familial Cardiovascular Diseases) was set up. Family members of index patients are no longer actively approached to be tested, and as a result the number of detected family members has decreased significantly. These study findings underline the importance of actively screening the family members of index patients, including children and adolescents.

20-Year Follow-up of Statins in Children with Familial Hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia is characterized by severely elevated low-density lipoprotein (LDL) cholesterol levels and premature cardiovascular disease. The short-term efficacy of statin therapy in children is well established, but longer follow-up studies evaluating changes in the risk of cardiovascular disease are scarce.

METHODS

We report a 20-year follow-up study of statin therapy in children. A total of 214 patients with familial hypercholesterolemia (genetically confirmed in 98% of the patients), who were previously participants in a placebo-controlled trial evaluating the 2-year efficacy and safety of pravastatin, were invited for follow-up, together with their 95 unaffected siblings. Participants completed a questionnaire, provided blood samples, and underwent measurements of carotid intima-media thickness. The incidence of cardiovascular disease among the patients with familial hypercholesterolemia was compared with that among their 156 affected parents.

RESULTS

Of the original cohort, 184 of 214 patients with familial hypercholesterolemia (86%) and 77 of 95 siblings (81%) were seen in follow-up; among the 214 patients, data on cardiovascular events and on death from cardiovascular causes were available for 203 (95%) and 214 (100%), respectively. The mean LDL cholesterol level in the patients had decreased from 237.3 to 160.7 mg per deciliter (from 6.13 to 4.16 mmol per liter) - a decrease of 32% from the baseline level; treatment goals (LDL cholesterol <100 mg per deciliter [2.59 mmol per liter]) were achieved in 37 patients (20%). Mean progression of carotid intima-media thickness over the entire follow-up period was 0.0056 mm per year in patients with familial hypercholesterolemia and 0.0057 mm per year in siblings (mean difference adjusted for sex, -0.0001 mm per year; 95% confidence interval, -0.0010 to 0.0008). The cumulative incidence of cardiovascular events and of death from cardiovascular causes at 39 years of age was lower among the patients with familial hypercholesterolemia than among their affected parents (1% vs. 26% and 0% vs. 7%, respectively).

CONCLUSIONS

In this study, initiation of statin therapy during childhood in patients with familial hypercholesterolemia slowed the progression of carotid intima-media thickness and reduced the risk of cardiovascular disease in adulthood. (Funded by the AMC Foundation.).

Efficacy and safety of ezetimibe monotherapy in children with heterozygous familial or nonfamilial hypercholesterolemia

OBJECTIVES

To evaluate the lipid-altering efficacy and safety of ezetimibe monotherapy in young children with heterozygous familial hypercholesterolemia (HeFH) or nonfamilial hypercholesterolemia (nonFH).

STUDY DESIGN

One hundred thirty-eight children 6-10 years of age with diagnosed HeFH or clinically important nonFH (low-density lipoprotein cholesterol [LDL-C] ≥ 160 mg/dL [4.1 mmol/L]) were enrolled into a multicenter, 12-week, randomized, double-blind, placebo-controlled study. Following screening/drug washout and a 5-week single-blind placebo-run-in with diet stabilization, subjects were randomized 2:1 to daily ezetimibe 10 mg (n = 93) or placebo (n = 45) for 12 weeks. Lipid-altering efficacy and safety were assessed in all treated patients.

RESULTS

Overall, mean age was 8.3 years, 57% were girls, 80% were white, mean baseline LDL-C was 228 mg/dL (5.9 mmol/L), and 91% had HeFH. After 12 weeks, ezetimibe significantly reduced LDL-C by 27% after adjustment for placebo (P < .001) and produced significant reductions in total cholesterol (21%), nonhigh-density lipoprotein cholesterol (26%), and apolipoprotein B (20%) (P < .001 for all). LDL-C lowering response in sex, race, baseline lipids, and HeFH/nonFH subgroups was generally consistent with overall study results. Ezetimibe was well tolerated, with a safety profile similar to studies in older children, adolescents, and adults.

CONCLUSIONS

Ezetimibe monotherapy produced clinically relevant reductions in LDL-C and other key lipid variables in young children with primary HeFH or clinically important nonFH, with a favorable safety/tolerability profile.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00867165.

Inheritance pattern of familial hypercholesterolemia and markers of cardiovascular risk

Studies in children and adults have resulted in conflicting evidence in the quest for the answer to the hypothesis that offspring from hypercholesterolemic mothers might have an increased cardiovascular risk. Previous studies might have suffered from limitations such as cohort size and clinical sampling bias. We therefore explored this hypothesis in large cohorts of both subjects with familial hypercholesterolemia (FH) and unaffected siblings in a wide age range. In three cohorts (cohort 1: n = 1,988, aged 0-18 years; cohort 2: n = 300, 8-30 years; cohort 3: n = 369, 18-60 years), we measured lipid and lipoproteins as well as carotid intima-media thickness (c-IMT) in offspring from FH mothers versus FH fathers. For LDL cholesterol, triglycerides (TGs), and c-IMT, we performed a pooled analysis. No significant differences could be observed in c-IMT, lipid, or lipoprotein levels from offspring of FH mothers versus FH fathers. Pooled analyses showed no significant differences for either LDL cholesterol [mean difference 0.02 (-0.06,0.11) mmol/l, P = 0.60], TGs [mean difference 0.07 (0.00,0.14) mmol/l, P = 0.08], or c-IMT [mean difference -0.00 (-0.01,0.01) mm, P = 0.86]. Our data do not support the hypothesis that cardiovascular risk markers are different between offspring from FH mothers and FH fathers.

Follow-up of children diagnosed with familial hypercholesterolemia in a national genetic screening program

OBJECTIVE

To assess the follow-up of children diagnosed as having familial hypercholesterolemia (FH) in the nationwide DNA-based cascade screening program (the Netherlands).

STUDY DESIGN

Questionnaires covering topics such as demographics, family history, physician consultation, and treatment were sent to parents of patients with FH (age 0-18 years), 18 months after diagnosis.

RESULTS

We retrieved 207 questionnaires of patients aged 10.9 ± 4.2 years (mean ± SD) at diagnosis; 48% were boys, and the mean low-density lipoprotein cholesterol (LDL-C) level at diagnosis was 167 ± 51 mg/dL. Of these patients, 164 (79%) consulted a physician: a general practitioner (35%), lipid-clinic specialist (27%), pediatrician (21%), internist (11%), or another physician (6%). LDL-C level at diagnosis and a positive family history for cardiovascular disease were independent predictors for physician consultation. Of the patients who visited a physician, 62% reported to have received lifestyle advice, and 43 (26%) were prescribed statin treatment. Independent predictors for medication use were age, LDL-C level, and educational level of parents.

CONCLUSION

The follow-up of children with FH after diagnosis established through cascade screening is inadequate. Better education of patients, parents, and physicians, with a structured follow-up after screening, should improve control of LDL-C levels and hence cardiovascular risk in children with FH.

Paediatric screening for hypercholesterolaemia in Europe

Different screening strategies are currently recommended to identify children with (familial) hypercholesterolaemia in order to initiate early lipid management. However, these strategies are characterised to date by low adherence by the medical community and limited compliance by parents and children. In a literature review, the authors assess which children should undergo screening and which children are in effect identified through the currently recommended strategies. Furthermore, the authors discuss the different screening tools and strategies currently used in Europe and what is known about the negative aspects of screening. The authors conclude that currently recommended selective screening strategies, which are mainly based on family history, lack precision and that a large percentage of affected children who are at increased risk of future coronary artery disease are not being identified. The authors propose universal screening of children between 1 and 9 years of age, a strategy likely to be most effective in terms of sensitivity and specificity for the identification of children with familial hypercholesterolaemia. However, this concept has yet to be proven in clinical practice.

Serum bilirubin levels in familial hypercholesterolemia: a new risk marker for cardiovascular disease?

Low concentrations of bilirubin are associated with an increased risk for cardiovascular disease (CVD). Possibly, bilirubin exerts its effect through the protection of LDL from oxidation. Therefore, we examined whether low bilirubin might also be a risk marker for CVD in patients with familial hypercholesterolemia (FH) and whether statins influence serum bilirubin levels. Patients with FH were recruited from 37 lipid clinics. After a washout period of 6 weeks, all patients were started on monotherapy with simvastatin 80 mg for a period of two years. A total of 514 patients were enrolled. Bilirubin at baseline was inversely associated with the presence of CVD, also after adjustment for age, gender, presence of hypertension, and HDL cholesterol levels. Moreover, bilirubin levels were significantly raised, by 7%, from 10.0 to 10.8 μmol/L after treatment with simvastatin 80 mg. We hypothesize first that high bilirubin levels might protect patients with FH from CVD. Furthermore, bilirubin levels were significantly increased after treatment with simvastatin 80 mg, independent of changes in liver enzymes, which might confer additional protection against CVD. Whether this is also true for lower doses of simvastatin or for other statins remains to be investigated.

Molecular Basis of Autosomal Dominant Hypercholesterolemia

Background—

Autosomal dominant hypercholesterolemia (ADH) is characterized by elevated low-density lipoprotein cholesterol levels and premature cardiovascular disease. Mutations in the genes encoding for low-density lipoprotein receptor ( LDLR ), apolipoprotein B ( APOB ), and proprotein convertase subtilisin/kexin 9 ( PCSK9 ) underlie ADH. Nevertheless, a proportion of individuals who exhibit the ADH phenotype do not carry mutations in any of these 3 genes. Estimates of the percentage of such cases among the ADH phenotype vary widely. We therefore investigated a large pediatric population with an unequivocal ADH phenotype to assess the molecular basis of hereditary hypercholesterolemia and to define the percentage of individuals with unexplained dyslipidemia.

Methods and Results—

We enrolled individuals with low-density lipoprotein cholesterol levels above the 95th percentile for age and gender and an autosomal dominant inheritance pattern of hypercholesterolemia from a large referred pediatric cohort of 1430 children. We excluded children with thyroid dysfunction, nephrotic syndrome, autoimmune disease, liver disease, primary biliary cirrhosis, and obesity (body mass index >75th percentile for age and gender), as well as children referred via a cascade screening program and those from families with a known molecular diagnosis. Of the 269 children who remained after the exclusion criteria were applied, 255 (95%) carried a functional mutation ( LDLR , 95%; APOB , 5%).

Conclusion—

In the vast majority of children with an ADH phenotype, a causative mutation can be identified, strongly suggesting that most of the large-effect genes underlying ADH are known to date.

Dilemmas in treatment of women with familial hypercholesterolaemia during pregnancy

Familial hypercholesterolaemia (FH) is a co-dominant monogenic disorder of lipoprotein metabolism, characterised by severely elevated levels of low-density lipoprotein cholesterol (LDL-C) from birth onwards. Treatment of FH patients with cholesterol-lowering medication is mandatory to prevent premature cardiovascular disease (CVD). As a result of a nationwide screening in the Netherlands, a large group of women with FH in the child-bearing age range has been identified. Physicians are faced with a treatment dilemma if these females present either with a wish for pregnancy or an established pregnancy, since all systemically absorbed lipid-lowering medication is contraindicated during pregnancy. Currently, no evidence-based guidelines exist on the optimal clinical approach in these patients. Animal studies have shown conflicting data on potential teratogenicity of statins. In humans, there is no strong adverse safety signal, but prospective studies are lacking. The consequences of maternal hypercholesterolaemia during pregnancy for both mother and child are not well determined, although it has been suggested that it may increase the risk of CVD in the offspring. This review describes two representative cases from clinical practice, and discusses clinical considerations for treating pregnant FH patients supplemented with what is known from the literature.