Familial Hypercholesterolemia, or Why We Should Measure the Lipid Profile in

Children

Martin HersbergerDivision of Clinical Chemistry and

Biochemistry

Dyslipidemias

Acquired forms (secondary 5%)

- Endocrine disorders- Intoxications- Organ faillure- Drugs- Food

Monogenic forms(primary 5%)Mutations in genes for

- Apolipoproteines- Enzymes- Transporters- Receptors

Combination (80%)Genetic predisposition (mostly polygenic)

in combination with environmental and behaviorial factors and/or disease

Lipid Metabolism

HDL3

HDL2

preβ-HDL

VLDL

IDL

LDL

Chylo

Chylo

CETP

LPL

LPL

LPL

LDLR

SR-BIHL

LCAT/PLTP

LCAT

Secondary Dyslipidemias Dyslipidemia Disease Food, Drugs

LDL-hypercholesterolemia Hypothyroidism Saturated fatty acidsCholestasis GestagensNephrotic syndromeAnorexia

Hypertriglyceridemia Diabetes mellitus Saturated fatty acidsRenal insufficiency Alcohol

Retinoids, estrogensSome diuretics

Mixed dyslipidemias Diabetes mellitus Saturated fatty acidsNephrotic syndrome Alcohol

Retinoids, estrogens, some diuretics

HDL-C reduction Diabetes mellitus AndrogensCancerInflammation

Hypercholesterolemia• VLDL-LDL metabolism (familial hypercholesterolemia)• Cholesterol resorption (sitosterolemia)• Cholesterol storage (Wolman-disease, CESD)

Hypertriglyceridemia• Lipolysis (chylomicronemia)

Hypocholesterolemia• Cholesterol synthesis (Smith-Lemli-Opitz-syndrome)• VLDL-LDL metabolism (Abeta-/Hypobetalipoproteinemia)• HDL metabolism (ApoA-I-, LCAT-deficiency, Tangier disease)

Monogenic Dislipidemias in Children and Adolescents

VLDL-LDL Metabolism

VLDL

IDL

LDL

LPL

LPL

LDLR

LDL

Familial Hypercholesterolemia(Handbuch der Fettstoffwechselstörungen, Schattauer Verlag, Stuttgart, 2007, 3. Auflage)

Lipid profile FH Lipid profile „normal“

0

2

4

6

8

10

12

TotalChol.

LDL-C HDL-C Trigl.

Premature CVDCo-dominant inheritance

XanthomasXanthelasmsArcus lipoides

mm

ol/L

mm

ol/L

Lipid elektrophoresis Clinical features

0

2

4

6

8

10

12

TotalChol

LDL-C HDL-C Trigl.

mm

ol/L

mm

ol/L

Clinical Features

Xanthoma tuberosum Xanthoma tendinosum

Arcus lipoides juvenilisXanthelasma

VLDL-LDL Metabolism

VLDL

IDL

LDL

LPL

LPL

LDLR

LDL

Familial Defective Apolipoprotein B100 R3500Q (FDB)

(J Clin Invest. 1998 Mar 1;101(5):1084-93)

Arg3500 Gln3500

Prevalence of the R3500Q Mutation (FDB) in the Apo-B Gene

(J Lipid Res. 1994 Apr;35(4):574-83)

Country Prevalence

USA 1 / 500

England 1 / 600

Germany 1 / 700Switzerland 1 / 209

Trait Lipid profile

mm

ol/L

0

2

4

6

8

10

12

TotalChol

LDL-C HDL-C Trigl.

mm

ol/L

Prevalence of the R3500W Mutation (FDB) in the Apo-B Gene

(J Clin Lipidol. 2016 Nov - Dec;10(6):1297-1302)

R3500W is prevalent in East Asians

Mutations in Apo-B100 leading toHypercholesterolemia?

(Atherosclerosis. 2004 May;174(1):11-6 / ATVB 2000 Oct;20(10):E76-82 / ATVB 1995 Aug;15(8):1025-9 / MolGenet Genomic Med. 2013 Sep;1(3):155-61 / Journal of Clinical Lipidology (2016) 10, 1297–1302)

Mutation Cholesterol(mmol/L)

Triglycerides(mmol/L)

LDL-C (mmol/L)

HDL-C (mmol/L)

Directinfluence

R3500Q/W/L 8.2 – 10.3 0.8 – 2.3 6.1 – 7.8 1.2 – 2.0 Yes

H3543Y 4.6 – 7.3 1.8 – 3.8 1.6 – 4.7 0.9 – 1.6 ?

R3531C 4.7 – 9.3 0.4 – 1.6 2.5 – 7.1 No

R50W 8.3 – 11.5 0.9 – 2.1 5.9 – 9.9 0.9 – 1.9 ?

Cave: hypercholesterolemia in children often not pronounced

Activating Mutations in the Protein Convertase Subtilisin/Kexin Type 9a (PCSK9) Gene result in FH3 (F216L)

(Nat Genet. 2003 Jun;34(2):154-6 / Clin Genet. 2004 May;65(5):419-22)

No patient has a mutation in the LDLR or has an ApoB3500 mutation

? ?

Age (years) 49 40Cholesterol mmol/L 12.3 5.6LDL-C mmol/L 10.0 3.4

Age (years) 28 5 3Cholesterol mmol/L 4.6 6.2 6.6LDL-C mmol/L 2.0 4.3 4.8

Inactivating Mutations in the PCSK9 Gene Result in Low LDL in African

Americans(Nature Genetics 37, 161 - 165 (2005) / Lancet Diabetes Endocrinol. 2016 Nov 28. pii: S2213-8587(16)30396-5)

* Significant difference

Parameter Normal (n=1769)

Mutant (n=33)

Cholesterol(mmol/L)

4.6 ± 1.1 3.6 ± 0.6*

LDL-C(mmol/L)

2.7 ± 1.0 1.6 ± 0.6*

Triglycerides(mmol/L)

1.2 ± 1.0 0.9 ± 0.4

HDL-C(mmol/L)

1.4 ± 0.4 1.6 ± 0.5

Cleaved and Secreted PCSK9 Directs the LDLR to the Lysosomes

(IUBMB Life, 62(2): 125–131, February 2010)

Autosomal RecessiveHypercholesterolemia (ARH)

(Science 2001;292(5520):1394-8 / J Atheroscler Thromb. 2010 Feb 26;17(2):131-40)

Recessive Inheritance

Mutations in the LDLRAP1 Gene

PTB: Phosphotyrosine binding domain forinteraction with the LDLR

Family Mutation Cholesterolmmol/L

ARH1 170X 13.8

ARH2 W22X 11.7-18.2

ARH3 Q136X 11.4-15.1

ARH4 P202H 13.5-15.9

ARH5 33X 16.6

ARH6 Thr56Met 7.1 (het)

The ARH Protein Is an Adaptor to Locatethe LDLR

(PNAS 2002;99(25):16099-104)

ARH binds LDLR,Clathrin and AP-2

Frequency of Gene Mutations Involved in Primary Hypercholesterolemia

(Appl Clin Genet. 2010 Aug 5;3:53-64.)

Dominant Frequency % Number of MutationsLDLR 60-80 ~1740Apo-B 1-5 ~4PCSK9 0-3 ~163Unknown 20-40

Recessive Frequency % Number of MutationsARH Rare ~39ABCG5 & 8 Rare ~50

FH in Children is Mainly Caused byMutations in the LDLR and in the

Apo-B100 Gene(Circulation 2011;123;1167-1173)

mm

ol/L

A mutation was found in 95% of the children, none in the PCSK9 gene

Selektive Screening for Dyslipidemias in Childrenand Adolescents (2-18 J)

(Pediatrics. 2008 Jul;122(1):198-208)

Positive family history for cardiovascular disease?Dislipidemia in one of the parents?

Lipid profile

AcceptableCholesterol: < 4.4 mmol/L

LDL-C: < 2.9 mmol/L

Control in 5 yearsReduction of risk factorsEducation on diet and sports

BorderlineCholesterol: 4.4 - 5.2 mmol/L

LDL-C: 2.9 - 3.4 mmol/L

HighCholesterol: > 5.2 mmol/L

LDL-C: > 3.4 mmol/L

Control in 1 yearReduction of risk factorsOptimizing diet and sports

Find the causeTherapeutic intervention (diet and ev. drugs)Cascade screening

Diagnosis of FH in Children and Adolescents(Eur Heart J. 2015 Sep 21;36(36):2425-37)

• Secondary causes of hypercholesterolemia should be ruled out• Family history of premature CHD plus high LDL-C levels are the two key

selective screening criteria: (F + H = FH) • A LDL-C level ≥5 mmol/L on two successive occasions after 3 months

diet indicates a high probability of FH. A family history of premature CHD in close relative(s) and/or baseline high cholesterol in one parent, together with an LDL-C ≥4 mmol/L indicates a high probability of FH. If the parent has a genetic diagnosis, an LDL-C ≥3.5 mmol/L suggests FH in the child

• DNA testing establishes the diagnosis. If a pathogenic LDLR mutation is identified in a first-degree relative, children may also be genetically tested (cascade screening)

• If a parent died from CHD, a child even with moderate hypercholesterolaemia should be tested genetically for FH and inheritedelevation in Lp(a)

ROC Analysis of LDL-Cholesterol in Children from FH Families

(Ciculation (2003) 107; 1473-1478)

60

80

100

0 20 40 60 80 100

Sens

itivi

ty

> 3.5 mmol/L

LDLC > 3.5 mmol/LSensitivity: 96% (95%-CI: 94-97%)

100 - Specifity591 Dutch families, 1034 children

> 4.0 mmol/L

> 3.0 mmol/L

Do We Diagnose FH Patients with this Strategy?(Eur Heart J. 2013 Dec;34(45):3478-90a)

Problems of the Selective Screening Strategy(Pediatrics 2008;122;198-208)

• With the strategy for the Selective Screening, 35-45% of thechildren had a lipid profile determined

• The Selective Screening is missing 30-60% of children and adolescents with hypercholesterolemia

• Parents often are too young for clinical signs of cardiovasculardisease

• Young parents often do not know their lipid profile or do not knowthe risk for cardiovascular disease from elevated LDL

• Family history often not known, not correctly remembered, oreven faked

Current Recommendations for Screening in Children and Adolescents

• Slovenia has introduced a general screening

• Germany recommends a general screening at the age of 11-13 years

• AHA recommends additional screening in children with obesity. Also check for the presence of the metabolic syndrome

• AAP recommends additional screening in children between 2-10 yearswith additional risk factors like obesity, hypertension, smoking, ordiabetes mellitus, and if family history is unclear

• NHLBI recommends general screening at the age of 9-11 years

• US Preventive Services Task Force recommends no general screening

• Screening should include a full lipid status including total cholesterol, HDL-cholesterol, (Non-HDL cholesterol) and triglycerides

Lifestyle Intervention

Treat Secondary Forms Hypocaloric andLipid Lowering Diet

Increase PhysicalActivity

- Endurance sports to burn fat and to change lipoprotein pattern

- Adjust insulin treatment- Treat hypothyroidism- Change contraception

- Low fat diet with fibers and unsaturated fatty acids

Reduce ModifiableRisk Factors

- Stop smoking- Reduce alcohol- Treat hypertension

Drug Treatment in FH Children(Eur Heart J. 2015 Sep 21;36(36):2425-37)

• For children aged 8-10 years, the Panel recommends that LDL-C is ideally reduced by 50% from pre-treatment levels

• For children aged ≥10 years, especially if there are additional cardiovascular risk factors, including elevated Lp(a), the target LDL-C should be <3.5 mmol/L

214 FH treated from childhood (n=214) compared with their FH parents treated from adulthood (n=156)

Pravastatin Reduces Intima Media Thickness in the Carotis of FH Children

(JAMA. 2004;292(3):331-337)

Reduction of Total and LDL-cholesterol

No difference between thegroups for: height, weight, BMI, testicular volume, liver enzymes, glucocorticoides, sex hormones, tanner stages

2 year randomized double-blind study in 214 children (8-18 years)

Statin Therapy Increases Event-FreeSurvival in FH Patients

(Eur Heart J. 2013 Dec;34(45):3478-90a)

Dutch FH patients according to statin treatment(413 on and 1537 off statin)

mm

ol/L

Phenotypic Variability of Homozygous FH(European Heart Journal (2014) 35, 2146–2157)

mm

ol/L

Novel Drugs to Lower LDL Cholesterol(European Heart Journal (2014) 35, 2146–2157)

(mipomersen)

(lomitapide)

(alirocumab / evolocumab)

Established and Novel Drugs in Homozygous FH

(European Heart Journal (2014) 35, 2146–2157)

mm

ol/L

The LDL-Cholesterol Burden(Eur Heart J. 2013 Dec;34(45):3478-90a)

Summary

• FH is associated with an increased risk for cardiovascular diseasecompared to polygenic hypercholesterolemia

• Without intervention 30-50% of FH patients will encounter a cardiovascularevent before 50 years of age

• Selective screening should not only been done in children und adolescentswith a family history for CVD but also in children and adolescents withobesity, hypertension, smoking, diabetes … or even as a generalscreening for all children between 5-10

• Cascade screening in FH families is recommended using genetics

• Lifestyle intervention should start in FH children after the second year of life

• Effective treatment is available and does reduce cardiovascular events

• Drug treatment for heterozygous FH should start from 8-10 years reachinga LDL-C <3.5 mmol/L

Thank you foryour attention!