Diagnosing heterozygous familial hypercholesterolemia using new practical criteria validated by molecular genetics

Inherited metabolic disorders and cerebral infarction

The association of genetic factors and cerebral infarction (CI) has long been established. A positive family history alone is a recognized risk factor for CI and vascular events in general. However, there are certain inherited conditions that further increase the risk of stroke. These conditions are generally metabolic and mitochondrial genetic defects that have variable modes of inheritance. This article reviews major inherited metabolic disorders that predispose an individual to CI. Ten main conditions will be discussed: Fabry's disease, cerebrotendinous xanthomatosis, tangier disease, familial hypercholesterolemia, homocystinuria, methylmalonic acidemia, glutaric aciduria type I, propionic acidemia, ornithine transcarbamylase deficiency and mitochondrial encephalopathy, lactic acidosis and stroke-like phenomenon.

Comparison of genetic versus clinical diagnosis in familial hypercholesterolemia

Early diagnosis is important in familial hypercholesterolemia (FH), a highly atherogenic condition, but internationally agreed clinical diagnostic criteria are lacking. Genetic testing for low-density lipoprotein (LDL) receptor (LDLR) and apolipoprotein B (APOB) gene defects is the preferable diagnostic method, but the best phenotype indication to proceed with genetic diagnosis has not been established. The aim of this study was to assess the predictive and accuracy values of standard diagnostic criteria for detecting disease-causing mutations in 825 subjects with clinical FH aged > or =14 years from 3 lipid clinics in Spain. All subjects underwent thorough genetic testing for the detection of LDLR and APOB defects using the Lipochip platform. FH-causing mutations were detected in 459 subjects (55.6%). By logistic regression analysis, familial or personal history of tendon xanthoma (TX) and LDL cholesterol were strongly associated with genetic diagnosis (p <0.005, R(2) = 0.41). In subjects without familial or personal histories of TX, the diagnostic criteria for FH of the Make Early Diagnosis to Prevent Early Deaths (MEDPED) project, based on age-specific LDL cholesterol thresholds, showed sensitivity of 72.4%, specificity of 71.1%, and accuracy of 71.6%. LDL cholesterol > or =190 mg/dl in subjects with familial or personal histories of TX and > or =220, > or =225, and > or =235 mg/dl in those without such histories aged <30, 30 to 39, and > or =40 years, respectively, showed sensitivity of 91.1%, specificity of 71.1%, and accuracy of 74.2% for a positive genetic diagnosis. This new set of diagnostic criteria for FH was validated in an independent group of 440 subjects from 6 additional Spanish lipid clinics. In conclusion, TX and age-adjusted LDL cholesterol cut-off values have the highest value for clinical diagnosis and indication of genetic testing in FH.

Diagnosis of heterozygous familial hypercholesterolaemia in children

BACKGROUND

Most children with familial hypercholesterolaemia (FH) are diagnosed by raised blood cholesterol levels, but the test lacks sensitivity and specificity. As such children have evidence of vascular dysfunction at an early age, correct identification of affected individuals is important so that treatment can be started.

AIM

To determine levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in children with genetically proven FH and their unaffected siblings, in order to identify a diagnostic cut-off point if possible.

DESIGN

Retrospective case-note survey.

METHODS

We studied the notes of 115 children aged 3-16 years, 69 proven FH and 46 unaffected sibs, 65 boys and 50 girls, from 31 families and 21 different mutations. Data recorded were age, sex, TC, and (when available) LDL-C.

RESULTS

The lowest TC level in an affected individual was 4.7 mmol/l and the highest in normal individual was 6.05 mmol/l. This overlap range included 21 children (18% of the total). The corresponding figures for LDL-C were 3.0 and 3.7 mmol/l, which included eight children (8%).

CONCLUSION

TC is not an effective test for differentiating affected and unaffected children with FH. LDL-C is better, but genetic testing remains the method of choice, especially if treatment decisions are to be taken.

Elevated serum soluble endoglin (sCD105) decreased during extracorporeal elimination therapy for familial hypercholesterolemia

Extracorporeal elimination is a method of LDL-lowering therapy that is used in severe familial hypercholesterolemia (FH) after other therapeutic approaches have failed. There are currently no universally accepted biomarkers that would allow determining necessary intensity of therapy and frequency of future therapeutic interventions. An ideal tool for immediate evaluation would be a readily measurable serum marker. We hypothesized that soluble endoglin (sCD105), a recently described indicator of endothelial dysfunction, may represent such a tool. Eleven patients with FH (three homozygous, eight heterozygous; Fredrickson type IIa, IIb) that have been monitored for 4.5+/-2.8 years were treated; eight by LDL-apheresis and three by hemorheopheresis. 40 sCD105 measurements were done, before and after two consecutive elimination procedures. Baseline serum sCD105 levels were significantly higher in the patients (5.74+/-1.47 microg/l in series I, 6.85+/-1.85 microg/l in series II) than in the control group (3.85+/-1.25 microg/l). They decreased to normal after LDL-elimination (p=0.0003) in all except for one patient. This return to normal was not due to a non-specific capture of endoglin in adsorption or filtration columns as demonstrated by measurement of sCD105 before and after passage through the elimination media. We conclude that the soluble endoglin levels in patients with severe FH remain elevated despite long-term intensive therapy and that they decrease after extracorporeal elimination. Endoglin can therefore serve as a marker for evaluation of the treatment efficacy and of the decreased atherosclerotic activity in patients with FH treated by extracorporeal LDL-cholesterol elimination.

Diagnosis of familial hypercholesterolemia in general practice using clinical diagnostic criteria or genetic testing as part of cascade genetic screening

BACKGROUND

Too few familial hypercholesterolemia (FH) patients are diagnosed. The most cost-effective strategy to diagnose FH is to examine first-degree relatives of already diagnosed patients. This is referred to as cascade genetic screening.

METHODS AND RESULTS

One thousand eight hundred and five first-degree relatives of index patients with molecularly defined FH consented to cascade genetic screening by the use of molecular genetic testing. Of these, 44.8% were mutation carriers and 55.2% were noncarriers. Only 44.2% of the mutation carriers were on lipid-lowering drugs at the time of genetic testing. Of these, only 9.4% had a value for total serum cholesterol below 5 mM. Among adult mutation carriers who were not on lipid-lowering treatment at the time of genetic testing, reductions in total serum cholesterol and low-density lipoprotein cholesterol of 18.4% (p < 0.0001) and 25.3% (p < 0.0001), respectively, were observed 6 months after genetic testing. It is assumed that this improvement in the lipid profile is due to a definite diagnosis obtained by molecular genetic testing. By using the results of genetic testing as the gold standard for diagnosis of FH, data from a questionnaire filled out by the relatives showed that the use of clinical criteria to diagnose FH in general practice had a sensitivity of 46.2% and a specificity of 88.0%.

CONCLUSIONS

The use of clinical diagnostic criteria to diagnose FH in general practice identifies only approximately 50% of FH patients. Molecular genetic testing as part of cascade genetic screening is an efficient tool to diagnose patients, leading to significant improvement in the lipid profile. It should therefore be implemented in clinical medicine.

LDLR and ApoB are major genetic causes of autosomal dominant hypercholesterolemia in a Taiwanese population

BACKGROUND/PURPOSE

Autosomal dominant hypercholesterolemia (ADH) is an autosomal dominant inherited disease characterized by an increase in low-density lipoprotein cholesterol levels and premature coronary heart disease, which can be caused by mutations in genes encoding the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9). There is scant information with regard to the role played by each gene in the Taiwanese ADH population, especially the newly discovered PCSK9 gene.

METHODS

We used coupling heteroduplex analysis based on a denaturing high performance liquid chromatography system and DNA sequencing to screen for the LDLR gene, APOB gene and PCSK9 gene in 87 ADH cases recruited from 30 unrelated Taiwanese families.

RESULTS

We did not find any mutation-causing variant of the PCSK9 gene in our cases and thus excluded PCSK9 as the major culprit mutation in these families. On the other hand, we identified six previously reported LDLR gene mutations (C107Y, D69N, R385W, W462X, G170X, V408M), two novel LDLR gene mutations (FsG631 and splice junction mutation of intron 10), and one known mutation (R3500W) and one novel missense mutation (T3540M) in the APOB gene that were present in 55 members from 18 ADH families (60%). R3500W, rather than R3500Q, could be the principle mutation responsible for familial defective apolipoprotein B in Taiwanese.

CONCLUSION

The results of our study reveal a characteristic mutation pattern of ADH in Taiwan, mainly in the LDLR and APOB genes. However, PCSK9 gene mutation may not be a major cause of ADH in our study population.

European guidelines on cardiovascular disease prevention in clinical practice: executive summary. Fourth Joint Task Force of the European Society of Cardiology and other societies on cardiovascular disease prevention in clinical practice (constituted by representatives of nine societies and by invited experts)

Other experts who contributed to parts of the guidelines: Edmond Walma, Schoonhoven (The Netherlands), Tony Fitzgerald, Dublin (Ireland), Marie Therese Cooney, Dublin (Ireland), Alexandra Dudina, Dublin (Ireland) European Society of Cardiology (ESC) Committee for Practice Guidelines (CPG):, Alec Vahanian (Chairperson) (France), John Camm (UK), Raffaele De Caterina (Italy), Veronica Dean (France), Kenneth Dickstein (Norway), Christian Funck-Brentano (France), Gerasimos Filippatos (Greece), Irene Hellemans (The Netherlands), Steen Dalby Kristensen (Denmark), Keith McGregor (France), Udo Sechtem (Germany), Sigmund Silber (Germany), Michal Tendera (Poland), Petr Widimsky (Czech Republic), José Luis Zamorano (Spain)

Document reviewers: Irene Hellemans (CPG Review Coordinator) (The Netherlands), Attila Altiner (Germany), Enzo Bonora (Italy), Paul N. Durrington (UK), Robert Fagard (Belgium), Simona Giampaoli(Italy), Harry Hemingway (UK), Jan Hakansson (Sweden), Sverre Erik Kjeldsen (Norway), Mogens Lytken Larsen (Denmark), Giuseppe Mancia (Italy), Athanasios J. Manolis (Greece), Kristina Orth-Gomer (Sweden), Terje Pedersen (Norway), Mike Rayner (UK), Lars Ryden (Sweden), Mario Sammut (Malta), Neil Schneiderman (USA), Anton F. Stalenhoef (The Netherlands), Lale Tokgözoglu (Turkey), Olov Wiklund (Sweden), Antonis Zampelas (Greece)

Two novel mutations 685del 1 and D129G in the low-density lipoprotein receptor gene in a compound heterozygote Chinese family with familial hypercholesterolemia

DNA sequencing analysis was used to scan the genes in a Chinese family with clinically diagnosed autosomal genetic hypercholesterolemia. Two mutations were identified in exon 4 of the low-density lipoprotein receptor gene, which is the possible molecular mechanism of etiology of the family. The proband's extremely high level of serum cholesterol and the related manifestations suggested that he was a familial hypercholesterolemia homozygote and that his parents were in a relatively milder condition. DNA sequencing revealed that the proband had an abnormal pattern of exon 4 of the low-density lipoprotein receptor gene due to a heterozygosity (A/G) at nucleotide 386 and a heterozygous single-base deletion (A) at 685. Nucleotide 386 is the second base of codon 129, and A-->G mutation (D129G) changed this codon from Asp(GAC) to Gly(GGC). The single-base deletion of A at 685 (685del 1) is a frameshift mutation. It changes the phase of triplets, so that all codons are misread after this site of mutation; consequently, the protein expressed by the gene must be abnormal in structure and function. DNA analysis of the other family members showed that the 2 mutations should be respectively located in different alleles of the proband. Both of the 2 mutations have not been reported previously.

Genetic susceptibility to heart disease in Canada: lessons from patients with familial hypercholesterolemia

Much of the recent progress in treating patients with heart disease due to narrowed coronary arteries has resulted from studying disease evolution in patients with rare monogenic forms of disease. For instance, autosomal dominant familial hypercholesterolemia (FH, MIM (Mendelian Inheritance in Man) 143890) typically results from heterozygous mutations in LDLR encoding the low-density lipoprotein (LDL) receptor. Deficient LDLR activity results in elevated circulating LDL cholesterol, which accumulates within blood vessel walls, forming arterial plaques that can grow and eventually occlude the arterial lumen. Heterozygous LDLR mutations are usually detected using exon-by-exon sequence analysis (EBESA) of genomic DNA, a technology that has identified approximately 50 mutations in heterozygous FH (HeFH) subjects in Ontario. However, approximately 35% of Ontario HeFH patients had no EBESA-identified LDLR mutation. The diagnostic gap relates both to the genetic heterogeneity of FH and also to inadequate sensitivity of EBESA to detect certain mutation types, such as large deletions or insertions in LDLR. By means of a dedicated method to detect copy number variations (CNVs), additional heterozygous mutations in LDLR ranging from approximately 500 to >15 000 bases were uncovered, accounting for most of the remainder of Ontario HeFH patients. The appreciation of the key role of genomic CNVs in disease coincides with recent genome-wide mapping studies demonstrating that CNVs are common in apparently healthy people. CNVs thus represent a new level of genomic variation that is both an important mechanism of monogenic disease and a contributor to genomic variation in the general population; as well, it may have implications for evolution, biology, and possibly susceptibility to common complex diseases.

Diagnosis of families with familial hypercholesterolaemia and/or Apo B-100 defect by means of DNA analysis of LDL-receptor gene mutations

BACKGROUND

One major problem of using hypercholesterolaemia alone as a primary criterion for diagnosing familial hypercholesterolaemia (FH) is that 15-40% of relatives may be misdiagnosed because plasma lipid levels in FH heterozygotes overlap with those in the general population.

SETTING

General Hospital/University of Vienna, Department of Pediatrics, Outpatient lipid clinic.

METHODS

As a part of the MED-PED (make early diagnosis-prevent early death) project we are currently investigating children, adolescents and their relatives who are suspected to be affected with FH in our out-patient clinic for metabolic diseases using MED-PED inclusion criteria and confirming the diagnosis by means of DNA analysis.

PATIENTS

263 patients with premature atherosclerosis and/or hypercholesterolaemia: 116 children (mean age 11.6 +/- 4.1 years; 57 girls and 59 boys) and 147 adults (64 women, mean age 41.5 +/- 13.7 years; 83 men, mean age 42.8 +/- 10.8 years).

RESULTS

119 patients with mutations have been detected; 56 children with either low density lipoprotein receptor (LDLR) and/or ApoB mutations (27 girls and 29 boys; mean total cholesterol (TC) 275 +/- 71 mg/dl, triglycerides (TG) 101 +/- 57 mg/dl, high-density lipoprotein cholesterol (HDL-C) 49 +/- 12 mg/dl, low-density lipoprotein cholesterol (LDL-C) 198 +/- 67 mg/dl) and one boy with a homozygous. LDLR mutation. A further 62 adults with LDLR and/or ApoB mutations were documented; 33 women (mean age 36.9 +/- 11.1 years; mean TC 283 +/- 76 mg/dl, TG 137 +/- 78 mg/dl, HDL-C 55 +/- 17 mg/dl, LDL-C 210 +/- 67 mg/dl) and 29 men (mean age 45.0 +/- 10.6 years; mean TC 301 +/- 87 mg/dl, TG 163 +/- 112 mg/dl, HDL-C 42 +/- 12 mg/dl, LDL-C 233 +/- 83 mg/dl). In 32 of these subjects (11 children (21%), 21 adults (42%)), serum lipid levels were lower than the diagnostic MED-PED limits adopted, so that they might have been misclassified without an additional DNA analysis.

CONCLUSION

In our study, diagnosis of FH and related disorders (ApoB-100 defect) by means of conventional laboratory methods missed at least 21% in children and 42% in adults affected with LDLR and/or ApoB gene mutations. Genetic FH diagnosis provides a tool for specific diagnosis of mutation carrier status.

Familial defective apolipoprotein B-100 in Slovakia: are differences in prevalence of familial defective apolipoprotein B-100 explained by ethnicity?

The objective of this study was to examine frequency of familial defective apo-B-100 (FDB, R3500Q mutation) in probands with the phenotype of familial hypercholesterolemia (FH) and in the general population of 40-year-old subjects in Slovakia and to characterize their lipid and clinical criteria and to compare the frequency of FDB with other populations. We identified 35 patients with FDB among 362 probands with clinical diagnosis of FH and two cases of FDB in the 40-year-old cohort of 2323 subjects from general Slovak population. Probands with FDB differed from those with FH only in plasma triglyceride concentrations (1.84+/-1.4 mmol/l versus 1.45+/-0.98 mmol/l, respectively, p<0.01). Evaluation of personal history of premature atherosclerosis did not show any differences (11.4% in FDB versus 20% in FH, p<0.16). The FDB patients had similar manifestation of xanthomatosis as the FH patients (17.1% versus 8.25%, p<0.25). The frequency of FDB of 9.7% found in the FH patients is among the highest of those reported to date. The frequency of R3500Q mutation of 0.09% found in Slovak 40-year-old subjects did not differ significantly from published population molecular data. Our comparison of estimated FDB frequencies with those which were found by DNA analysis demonstrated that estimated frequencies were not only wider in range, but also significantly higher than those which were assessed by the analysis. The definitive answer to the prevalence of FDB and its biochemical and clinical characteristics requires screening of unbiased samples of the general population from different ethnic groups based on molecular genetic methods.

Autoantibody titers against OxLDL are correlated with Achilles tendon thickness in patients with familial hypercholesterolemia

Achilles tendon xanthomas are associated with increased cardiovascular risk in patients with familial hypercholesterolemia (FH). Oxidized low density lipoprotein (OxLDL), the antibodies against OxLDL, and the LDL-associated phospholipase A(2) (Lp-PLA(2)) may play important roles in atherogenesis. We investigated the possible association between plasma levels of OxLDL, Lp-PLA(2) activity, and autoantibody titers against various types of mildly OxLDL with Achilles tendon thickness (ATT). ATT was determined by sonography in 80 unrelated heterozygous FH patients. Three different types of mildly OxLDL were prepared: OxLDL(L), OxLDL(P), and OxLDL(D), at the end of the lag, propagation, and decomposition phases of oxidation, respectively. Similar types of OxLDL were also prepared after inactivation of the LDL-associated Lp-PLA(2). These types were denoted OxLDL(-)(L), OxLDL(-)(P), and OxLDL(-)(D). FH patients exhibited significantly higher plasma OxLDL levels and serum IgG titers against OxLDL(P) and OxLDL(D) compared with 40 normolipidemic apparently healthy controls. ATT values were positively correlated with autoantibody titers against OxLDL(P) and OxLDL(D); however, in multiple regression analysis, ATT was independently associated only with the autoantibody titers against OxLDL(D). We conclude that the IgG autoantibody titers against OxLDL(D) but not OxLDL or Lp-PLA(2) may play an important role in the pathogenesis of Achilles tendon xanthomas in FH patients.

Disease knowledge and adherence to treatment in patients with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is one of the most common genetic metabolic disorders and is associated with a high risk of premature coronary heart disease. Primary prevention directed at lifestyle changes, combined with preventive medical treatment, is the most important way to reduce the risk of coronary heart disease in individuals with FH. Knowledge about the condition and adherence to drug treatment may facilitate reaching treatment goals.

OBJECTIVE

The purpose of this study was to describe disease knowledge and adherence to treatment in patients with FH.

SUBJECTS AND METHODS

Seventy-four patients, more than 18 years of age, with FH were asked to participate. A questionnaire on disease knowledge about FH and adherence to drug treatment was sent to the patients. Response rate was 92% (n = 68). Drug treatment, laboratory results, blood pressure, and smoking were also documented.

RESULTS

Most patients knew about cholesterol, prevention, and the reason for drug treatment but were less informed about the risk of genetic transmission and family history. No significant correlation was found between knowledge and low-density lipoprotein cholesterol level. A significant, negative correlation between adherence and low-density lipoprotein cholesterol level was found (r = -.354, P < .01).

CONCLUSIONS

Patients with FH had scant understanding about the risk of genetic transmission and family history. High adherence to drug prescription has significant correlation to low-density lipoprotein cholesterol level.

Contemporary management of dyslipidemia in high-risk patients: targets still not met

PURPOSE

Our objective was to evaluate treatment patterns and the attainment of current National Cholesterol Education Program (NCEP)-recommended lipid targets in unselected high-risk ambulatory patients.

METHODS

Between December 2001 and December 2004, the prospective Vascular Protection and Guidelines Oriented Approach to Lipid Lowering Registries recruited 8056 outpatients with diabetes, established cardiovascular disease (CVD), or both, who had a complete lipid profile measured within 6 months before enrollment. The primary outcome measure was treatment success, defined as the achievement of LDL-cholesterol<2.6 mmol/L (100 mg/dL) according to NCEP guidelines. We examined patient characteristics and use of lipid-modifying therapy in relation to treatment outcome, which included the recently proposed optional LDL-cholesterol target (<1.8 mmol/L [70 mg/dL]) for very high-risk patients.

RESULTS

Overall, 78.2% of patients were treated with a statin and 51.2% had achieved the recommended LDL-cholesterol target. Treatment success rate was highest in diabetic patients with CVD (59.6%), followed by nondiabetic patients with CVD (51.8%), and lowest (44.8%) in diabetic patients without CVD (P<.0001). Compared with untreated patients, those on statins were more likely to achieve target (34.4% vs 55.9%, P<.0001). Of the patients who failed to meet target, only 9.9% were taking high-dose statin, while 29.3% were not prescribed any statin therapy. Among very high-risk patients, 20.8% attained the optional LDL-cholesterol goal. In multivariable analysis, advanced age, male sex, diabetes, coronary artery disease, coronary revascularization, and use of statin were associated with treatment success (all P<.0001).

CONCLUSION

Despite the well-established benefits of available lipid-modifying drugs, current management of dyslipidemia continues to be suboptimal, with a substantial proportion of patients failing to achieve guideline-recommended lipid targets. There remains an important opportunity to improve the quality of care for these high-risk patients.

Mutational heterogeneity in low-density lipoprotein receptor gene related to familial hypercholesterolemia in Morocco

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant disorder caused by mutations in the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. Until now, molecular data concerning FH in Morocco is still limited. To gain more information in this field and to assess the contribution of these three genes in the cause of FH determinism, we analyzed six unrelated Moroccan probands and twenty-five of their family's members.

METHODS

After LDLR and APOB genotype analysis, we screened the LDLR gene for mutations using southern blot and PCR-sequencing analysis. We also screened the APOB gene for the two common mutations R3500Q and R3531C by PCR-mediated site-directed mutagenesis. The PCSK9 gene was analyzed by direct sequencing.

RESULTS

We identified three novel mutations (C25X, IVS3+5G>T, D558A) and two mutations previously described (D151N, A480E) in the LDLR gene. The R3500Q and R3531C mutations are absent in our probands and for 1 proband, the implication of LDLR, APOB and PCSK9 genes was excluded, supporting the implication of a fourth gene in the determination of FH.

CONCLUSION

These data are in agreement with our previous study that suggests a heterogeneous mutational spectrum of FH in Morocco.

Heterozygous familial hypercholesterolemia: an underrecognized cause of early cardiovascular disease

Heterozygous familial hypercholesterolemia (HeFH) is a monogenic disorder that affects about 1 in 500 people, with a higher prevalence in certain subpopulations such as people of Quebecois, Christian Lebanese and Dutch South Afrikaner extraction. HeFH is characterized by cholesterol deposits affecting the corneas, eyelids and extensor tendons; elevated plasma concentrations of low-density lipoprotein (LDL) cholesterol; and accelerated vascular disease, especially coronary artery disease (CAD). Although HeFH is genetically heterogeneous, it is most often caused by heterozygous mutations in the LDLR gene encoding the LDL receptor. We describe a man who was diagnosed with HeFH after he had a myocardial infarction at 33 years of age. By DNA sequence analysis, he was found to have a heterozygous splicing mutation in his LDLR gene. This discovery expanded the growing mutational spectrum in patients with HeFH in Ontario. Given that HeFH is a treatable cause of early vascular disease, it is important that this condition be recognized, diagnosed and treated in affected patients; but as yet, there is no consensus on the best approach. Diagnostic criteria based on family history and clinical presentation have been proposed for patients with suspected HeFH. Biochemical or molecular screening might be considered to detect new cases of HeFH in populations with a relatively high HeFH prevalence and a relatively small number of possible causative mutations. So far, however, the most cost-effective and efficient systematic strategy to detect previously undiagnosed cases of HeFH is still cascade testing: clinical and biochemical screening of close relatives of the proband patient diagnosed with HeFH. Pharmacologic treatment of HeFH is cost-effective.

Genetic heterogeneity of autosomal dominant hypercholesterolemia in Mexico

BACKGROUND

Familial hypercholesterolemia (FH) and familial defective apolipoprotein B-100 (FDB) are relatively common lipid disorders caused by mutations of the low-density lipoprotein receptor (LDLR) and apolipoprotein B (apoB) genes, respectively. A third locus on chromosome 1p34.1-p32 was recently linked to FH and the responsible gene has been identified [protein convertase subtilisin/kexin type 9 (PCSK9)].

METHODS

We assessed the contribution of the LDLR, apoB, and PCSK9 genes as cause of FH in Mexico. Forty six unrelated probands, as well as 68 affected and 60 healthy relatives, were included.

RESULTS

All index cases were diagnosed as having heterozygous autosomal dominant FH. Seventeen of the 46 index cases had LDLR gene mutations, four of which were novel (Fs92ter108, C268R, Q718X, and Fs736ter743); and only one patient had an apoB mutation (R3500Q). We sequenced the PCSK9 gene in the remainder of the 28 probands with no identified LDLR or APOB gene defects; however, no PCSK9 mutations were found, including one large kindred with positive linkage to the 1p34.1-32 locus (multipoint LOD score of 3.3) and two small pedigrees. Linkage was excluded from these three loci in at least four kindreds suggesting that other yet uncharacterized genes are involved.

CONCLUSIONS

Our results underline substantial genetic heterogeneity for FH in the Mexican population.

Hyperlipidemia

Over the past 20 years, a link between lipoprotein disorders and atherosclerosis, and its clinical manifestations of myocardial infarction, stroke, and sudden cardiac death, has been conclusively demonstrated. This article reviews lipoprotein metabolism, its pathophysiology, describes an approach for the management of patients with lipid disorders and discusses therapy using the ATP III guidelines.

Cascade genetic screening for familial hypercholesterolemia

Familial hypercholesterolemia (FH) is caused by a mutation in the low-density lipoprotein receptor gene and is characterized by hypercholesterolemia, xanthomas, and premature coronary heart disease. Heterozygotes typically have values for total serum cholesterol in the range of 7-15 mmol/l and efficient lipid-lowering drug therapy is available. However, only approximately 20% of patients are diagnosed and less than 10% are being adequately treated. The most cost-effective strategy to diagnose patients with FH is to screen close relatives of patients already diagnosed with FH. This is referred to as cascade genetic screening. This review focuses on organization of a cascade genetic screening program for FH as well as cost-efficiency assessments, health benefits, possible adverse effects, and the screening of children. The author concludes that cascade genetic screening for FH leads to health benefits and is cost-effective without causing psychological or social damage. Accordingly, national cascade genetic screening programs for FH should be part of ordinary health care.

Cutoff point separating affected and unaffected familial hypercholesterolemic patients validated by LDL-receptor gene mutants

Familial hypercholesterolemia (FH) results from low-density lipoprotein (LDL) receptor gene mutations. Heterozygotes have twice normal LDL-cholesterol concentrations in early childhood, and experience early myocardial infarction. We demonstrated bimodal cholesterol frequency distributions, independently confirming existence of an identifiable hypercholesterolemic subpopulation. We assayed blood lipids in 181 FH patients genetically diagnosed and 100 unaffected relatives. Receiver operating characteristics curves were constructed. Total cholesterol and LDL-cholesterol concentrations showed bimodality. A total cholesterol cutoff of 225 mg/dl produced results agreeing with DNA testing (specificity, 98.5%; sensitivity, 99.4%). An LDL-cholesterol cutoff of 161-163 mg/dl produced 98.5% specificity and 98.3% sensitivity. Areas under curves were 0.9826 +/- 0.0058 for total cholesterol, and 0.9852 +/- 0.0043 for LDL-cholesterol. In conclusion, we define total cholesterol and LDL-cholesterol levels of 225 and 160 mg/dl, respectively, as cutoff points of normal subjects and FH patients.

The use of Achilles tendon sonography to distinguish familial hypercholesterolemia from other genetic dyslipidemias

OBJECTIVE

Achilles tendon (AT) xanthomas, specific for familial hypercholesterolemia (FH), may be clinically undetectable. We assessed the usefulness of AT sonography in the diagnosis of FH.

METHODS AND RESULTS

Sonographic AT characteristics were evaluated in 127 subjects with FH (81 genetically ascertained), 84 familial combined hyperlipidemia, 79 polygenic hypercholesterolemia, and 88 normolipidemic controls. Abnormal echostructure (sonographic xanthoma) was noted only in FH. AT thickness was higher (P<0.001) in FH men and women compared with all of the other groups and, in FH mutation carriers but not in others, correlated positively with low-density lipoprotein cholesterol (r=0.345; P<0.001) and negatively with high-density lipoprotein cholesterol (r=-0.265, P=0.015). Thickness thresholds for the diagnosis of FH with specificity >80%, as were derived from receiver operating curves, were 5.3 and 5.7 mm in men < and >45 years, and 4.8 and 4.9 mm in women < and >50 years, respectively. In FH mutation carriers, sonographic findings increased the clinical diagnosis of xanthomas from 35 (43%) to 55 (68%). Using thresholds in validation sets of 70 genetically identified FH and 54 dyslipidemic non-FH correctly classified 80% and 88%, respectively.

CONCLUSIONS

Sonographic AT characteristics are normal in non-FH dyslipidemias. Identification of suspected FH by ultrasound using sex- and age-specific AT thickness thresholds is recommended.

Implementation of cascade testing for the detection of familial hypercholesterolaemia

PURPOSE OF REVIEW

Cascade testing is an important method for identifying individuals at risk of a genetic condition. Recent advances in its application to familial hypercholesterolaemia are reviewed to identify potential problems impeding its application and the extent to which current data address these concerns.

RECENT FINDINGS

Different paradigms for cascade testing are being applied in national programmes. Current data demonstrates cost-effectiveness, and an increased uptake of preventive measures. The relationship between molecular and clinical diagnostic methods is discussed. Psychological impacts of a diagnosis of familial hypercholesterolaemia are in line with the risks associated with the disorder. The efficacy of statins in improving vascular function of children with familial hypercholesterolaemia has been demonstrated, but extensive safety data are lacking. Ethical arguments support that it is equally acceptable for relatives of familial hypercholesterolaemia patients to be contacted by healthcare workers as by family members, but the former is likely to be more efficient. Concerns about increased life insurance premiums are valid but insurance companies are assessing risk realistically, so this should not be a barrier to cascade testing.

SUMMARY

Current data support the implementation of cascade testing for familial hypercholesterolaemia as being feasible and cost-effective, but national implementation is limited to a small number of countries. Funding and the infrastructure to support it may be the major stumbling blocks in implementing this technique in many countries. Concerns about the ethics of carrying out cascade testing, and the potential psychological damage of DNA testing, appear to have been largely addressed for familial hypercholesterolaemia.

Sudden unexplained death: heritability and diagnostic yield of cardiological and genetic examination in surviving relatives

BACKGROUND

Sudden death mostly follows from cardiac disorders that elicit lethal ventricular arrhythmias. In young individuals, it often remains unexplained because history and/or postmortem analysis are absent or provide no clue. Because such sudden unexplained deaths (SUDs) may have heritable causes, cardiological and genetic assessment of surviving relatives of SUD victims may reveal the underlying disease and unmask presymptomatic carriers. We aimed to establish the diagnostic yield of such assessments.

METHODS AND RESULTS

We investigated 43 consecutive families with > or =1 SUD victim who died at < or =40 years of age. All studied relatives underwent resting/exercise ECG and Doppler echocardiography. Molecular genetic analysis was conducted to confirm the diagnosis. We identified an inherited disease and likely cause of death in 17 of 43 families (40%). Twelve families had primary electrical disease: catecholaminergic polymorphic ventricular tachycardia (5 families), long-QT syndrome (4 families), Brugada syndrome (2 families), and long-QT/Brugada syndrome (1 family). Furthermore, we found arrhythmogenic right ventricular cardiomyopathy (3 families), hypertrophic cardiomyopathy (1 family), and familial hypercholesterolemia (1 family). Molecular genetic analysis provided confirmation in 10 families. Finding the diagnosis was more likely when more relatives were examined and in families with > or =2 SUD victims < or =40 years of age. The resting/exercise ECG had a high diagnostic yield. These efforts unmasked 151 presymptomatic disease carriers (8.9 per family).

CONCLUSIONS

Examination of relatives of young SUD victims has a high diagnostic yield, with identification of the disease in 40% of families and 8.9 presymptomatic carriers per family. Simple procedures (examining many relatives) and routine tests (resting/exercise ECG) constitute excellent diagnostic strategies. Molecular genetics provide strong supportive information.

The relationship of molecular genetic to clinical diagnosis of familial hypercholesterolemia in a Danish population

The genes encoding the LDL receptor and apoB were screened for mutations associated with familial hypercholesterolemia (FH) in 408 patients referred to the Lipid Clinic in 1995-2003. The study aimed at testing the ability of three different sets of clinical criteria to predict the results of molecular genetic analysis, and secondly test whether population-based age- and sex-specific percentiles of LDL-cholesterol offer useful supplemental information in the selection of patients for molecular genetic analysis. The patients were retrospectively categorised according to Simon Broome Register Group criteria, Make Early Diagnosis to Prevent Early Death criteria (MEDPED) and the Dutch Lipid Clinic Network criteria, and the distribution of patients was compared to the results of the molecular genetic analysis. The study illustrates a classical dilemma. Mutation detection rates (and specificities) are high only if sensitivity is very low and vice versa: to find most mutation carriers, even patients with only possible FH must be examined by molecular genetic testing leading to mutation detection rates as low as 30-40%.

Familial hypercholesterolemia: ethical, practical and psychological problems from the perspective of patients

The main aim of the study was to explore the extent to which familial hypercholesterolemia (FH) influences the life of the patients affected. The study employed a qualitative analysis of semi-structured interviews with 23 outpatients who were being treated following a diagnosis of heterozygous FH at a tertiary hospital in Göteborg, Sweden. Some interviewees reported concerns related to their medication and feelings of guilt when not complying with treatment recommendations. However, none of the respondents expressed sustained emotional distress or would have preferred to be ignorant of their diagnosis. Apart from being more observant about food intake, their awareness of FH did not appear to have had a substantial impact on their way of life. In fact, those who did not suffer from any other diseases generally regarded themselves as healthy. Discussing the genetic constitution with family members with whom they had close contact was natural, but informing distant family members was not.

Simultaneous detection of multiple familial hypercholesterolemia mutations facilitates an improved diagnostic service in South african patients at high risk of cardiovascular disease

AIM

DNA testing can provide a definitive diagnosis of familial hypercholesterolemia (FH), even in the absence of the clinical characteristics of this inherited cardiovascular disease (CVD) subtype. Our aim was to design a rapid diagnostic assay capable of simultaneously analyzing seven point mutations in the low-density lipoprotein receptor (LDLR) gene, which occur at high frequency in South African FH patients.

METHODS

The test is based on multiplex DNA amplification and hybridization to membrane strips presenting a parallel array of immobilized allele-specific oligonucleotide probes.

RESULTS

A reverse-hybridization assay for genotyping LDLR point mutations D154N, D200G, D206E, C356Y, G361V, V408M, and P664L was set-up and validated using pretyped human DNA samples, as well as recombinant plasmid clones containing mutant alleles. The procedure is rapid (6 hours) and may be automated to a large extent.

CONCLUSIONS

The new FH strip-assay forms an important part of the comprehensive cardiovascular genetic screen offered routinely to high-risk population groups in South Africa. A genetic approach based on FH testing in conjunction with other 'genetic' CVD risk factors is feasible and justified, since the spectrum of disease-related mutations have been defined to a large extent in the genetically distinct population groups of South Africa. Knowledge of a significantly increased CVD risk due to the presence of gene variations, which can be targeted for risk reduction by the avoidance of relevant environmental risk factors and the appropriate treatment, provides a powerful message to motivate people into implementing preventative measures based on their genetic profile.

Risk assessment and strategies to achieve lipid goals: lessons from real-world clinical practice

Coronary heart disease (CHD) risk assessment to establish risk category and appropriate plasma lipid goals as well as achievement of those lipid goals, are important elements of treatment for dyslipidemia in clinical practice. Cases from clinical practice are presented to illustrate risk assessment and treatment in the settings of peripheral arterial disease (PAD) and heterozygous familial hypercholesterolemia (hFH). Patients with PAD are at high risk of CHD and cardiovascular mortality and may require aggressive lipid-lowering therapy irrespective of the degree of hypercholesterolemia at presentation. Risk in patients with hFH is not adequately reflected in population-based risk algorithms. Patients who have hFH should be considered at high risk for developing CHD and given aggressive lipid-modifying therapy, and family screening should be undertaken for additional case finding.

Screening for point mutations in the LDL receptor gene in Bulgarian patients with severe hypercholesterolemia

Familial hypercholesterolemia (FH) is a common, autosomal dominant disorder of lipid metabolism, caused by defects in the receptor-mediated uptake of LDL (low-density lipoproteins) due to mutations in the LDL receptor gene ( LDLR). Mutations underlying FH in Bulgaria are largely unknown. The aim of the present study was to provide information about the spectrum of point mutations in LDLR in a sample of 45 Bulgarian patients with severe hypercholesterolemia. Exons 3, 4, 6, 8, 9, and 14, previously shown to be mutational hot spots in LDLR, were screened using PCR-single-strand conformation polymorphism (SSCP). Samples with abnormal SSCP patterns were sequenced. Three different, hitherto undescribed point mutations (367T>A, 377T>A, 917C>A) and two previously described mutations (858C>A and 1301C>T) in eight unrelated patients were identified; four of the detected point mutations being missense mutations and one, a nonsense mutation. One of the newly described point mutations (917C>A) is a base substitution at a nucleotide position, at which two other different base substitutions have already been reported. Thus, all three possible base substitutions at this nucleotide position have been detected, making it a hot spot for point mutations causing FH. This is the first such mutational hot spot described in exon 6 of LDLR.

Guidelines for the diagnosis and management of heterozygous familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder of lipoprotein metabolism characterized by very high plasma concentrations of low density lipoprotein cholesterol (LDLc), tendon xanthomas and increased risk of premature coronary heart disease (CHD). FH is a public health problem throughout the world. There are 10,000,000 people with FH worldwide, mainly heterozygotes, and approximately 85% of males and 50% of females with FH will suffer a coronary event before 65 years old if appropriate preventive efforts are not implemented. Early identification of persons with FH and their relatives, and the early start of treatment are essential issues in the prevention of premature cardiovascular disease (CVD) and death in this population. However, guidelines for the general population formally exclude FH from their diagnostic and treatment recommendations. These guidelines have been elaborated by a group of international experts with the intention to answer the main questions about heterozygous FH (heFH) subjects that physicians worldwide face in the diagnosis and management of these patients.

Apolipoprotein B as a Marker of Familial Hyperlipoproteinemia

AIMS

Families with 10-12-year-old schoolchildren were informed about and asked to participate in a study to identify children with hyperlipoproteinemia. We hypothesised that children and families with familial blood lipid abnormalities, specifically those with familial hypercholesterolemia (FH) and familial combined hyperlipidemia (FCHL), could be identified by the child's apolipoprotein B level exceeding the 95th percentile.

METHODS

Written information and consent was distributed to the families. Families whose child had an apoB concentration exceeding the 95th percentile were further examined. Children and parents were divided into normal, high and very high low density lipoprotein cholesterol (LDLC) groups. In adults a high LDLC level was defined as > 4.1-4.9, a very high as > 4.9 mmol/l, in children as > 3.4-4.1 and > 4.1 mmol/l, respectively. The triglyceride level was regarded as high when > 3.6 mmol/l.

RESULTS

Of 2,855 families, 2,186 agreed to participate. The 95th percentile apoB level was for boys 0.98 and girls 1.07 g/l. Of the 131 children with an apoB level above the 95th percentile, 109 families accepted further examinations. Of 109 hyperapoB children 23 were obese. Normal LDLC was found in 28 hyperapo B children of whom six parents had high/very high LDLC and one high triglyceride concentrations. A high LDLC level was found in 52 children of whom 23 parents had higy/very high LDLC and another five high LDLC and/or high triglyceride concentrations. A very high LDLC level was found in 29 children, in two of them due to hypothyroidism, 17 had a parent with high/very high LDLC and another two parents a high triglyceride concentration. Familial hypercholesterolemia, defined as a LDLC concentration above twice the normal one in the child and a very high level in a parent, was suspected in six families, five having a relative with premature CHD. The families with FCHL should be included in the 20 families with hyperapoB and a child with high-very high LDLC and a parent with very high LDLC or TG levels.

CONCLUSION

Of the 109 children examined due to the child's increased apoB concentration, about 20% were obese and 75% had an increased LDLC concentration. A familial occurrence of hyperlipoproteinemia was evident in about 50% of the families with an hyperapoB child. Six families probably suffer from familial hypercholesterolemia. The definite number of FCHL families could not be defined since extended pedigrees were not available. A high suspicion of FCHL was evident in 20 families. ApoB is an important marker of hyperlipoproteinemia of familial occurrence identifying families in need of primary CHD prevention.

A pedigree analysis of familial hypercholesterolemia in monozygote twin brothers

The current study was designed to investigate the features of a family with familial hypercholesterolemia (FH). Twenty members of 3 generations in a family with hypercholesterolemia were enrolled in the study. The data collected were from clinical observation and subjected to pedigree analysis. The proband was a 41-year-old male who suffered from angina pectoris with multi-vessel stenosis of coronary arteries at the age of 40. Among 20 members, 8 individuals had FH in this family with a total incidence of 40% (54.5% [6/11] in male and 22.2% [2/9] in female). The serum total cholesterol level was increased in childhood from 7.1 to 10.8 mmol/L and tended to increase with increasing age. In addition, the level of total cholesterol was increased in monozygote twin brothers and their offspring in the family. This pedigree analysis showed that FH appears to be a hereditary disease of autosomal dominance, and attention should be paid, especially in the only son or daughter society of China.

Hypercholesterolemia blunts forearm vasorelaxation and enhances the pressor response during acute systemic hypoxia

OBJECTIVE

During hypoxia, active substances released by the endothelium play a key role in the cardiovascular and respiratory responses elicited to optimize oxygen delivery. As hypercholesterolemia is a major cause of endothelial dysfunction, it may interfere with these responses.

METHODS AND RESULTS

We studied cardiovascular and ventilatory responses to acute systemic hypoxia in 14 patients with hypercholesterolemia (HC) and 13 control (CO) subjects. Oxygen saturation decreased similarly in both groups. Diastolic blood pressure increased only in the HC group (P=0.0002) and, despite systolic blood pressure increases both in the HC group, 140+/-4 (95% confidence interval [CI],131 to 149 mm Hg) to 154+/-4 mm Hg (95% CI,145 to 164 mm Hg), and in the CO group, 133+/-3 (95% CI,126 to 140 mm Hg) to 140+/-4 mm Hg (95% CI,132 to 148 mm Hg), the HC group showed an enhanced pressor response (P=0.03, group comparison). Both groups had increased forearm blood flow, but the decrease in forearm vascular resistance in the CO group, 40+/-5 (95% CI, 30 to 51 UR) to 31+/-4 UR (95% CI,23 to 39 UR) (P=0.0001) was not seen in the HC group, 29+/-3 (95% CI, 22 to 37 UR) to 26+/-3 UR (95% CI, 20 to 33 UR), (P=0.03, group comparison).

CONCLUSIONS

Hypercholesterolemic patients demonstrate a hyperreactive pressor response and absence of forearm vasodilation during acute systemic hypoxia.

Coronary artery disease risk in familial combined hyperlipidemia and familial hypertriglyceridemia: a case-control comparison from the National Heart, Lung, and Blood Institute Family Heart Study

BACKGROUND

Conventional wisdom suggests that a diagnosis of familial combined hyperlipidemia (FCHL) carries a substantially greater risk of premature coronary artery disease (CAD) than a diagnosis of familial hypertriglyceridemia (FHTG). However, no population-based studies have critically addressed this issue.

METHODS AND RESULTS

FCHL and FHTG were diagnosed in 10.2% and 12.3% of 334 random control families and in 16.7% and 20.5% of 293 families with at least one case of premature CAD. The diagnosis of either FCHL or FHTG in an individual was associated with an odds ratio for CAD of 2.0 (P=0.003 and 0.002, respectively). However, odds ratios for premature CAD associated with both lipid disorders decreased substantially and identically with further adjustment for hypertension, diabetes, and especially HDL cholesterol, triglycerides, or apolipoprotein B. Similar results were found for differences in carotid intima-medial thickness and ankle-brachial index. Metabolic syndrome was identified in 65% of FCHL and 71% of FHTG patients compared with 19% in controls without FCHL or FHTG and was associated with an odds ratio of 3.3 (P<0.0001). The increased prevalence of the metabolic syndrome alone could account for the elevated CAD risk associated with both FCHL and FHTG.

CONCLUSIONS

FCHL and FHTG appear more alike than dissimilar. Further, the risk of CAD in FCHL and FHTG was strongly related to features of the metabolic syndrome. These findings suggest that the hypertriglyceridemia in FHTG is not benign and may warrant a change in epidemiological, genetic, and clinical approaches to these lipid disorders.

DNA testing for familial hypercholesterolemia: improving disease recognition and patient care

Cardiovascular disease is the leading cause of death worldwide and, like most chronic diseases, it has major genetic and environmental components. Among patients with coronary heart disease onset before the age of 55, about 5% of cases are attributable to heterozygous familial hypercholesterolemia (FH), a disease following autosomal dominant inheritance. About 50% of individuals with FH die before the age of 60 due to myocardial infarction. The frequency of FH is estimated to be 1 : 500. FH is related to mutations in the low-density lipoprotein (LDL)-cholesterol LDL-receptor gene and apolipoprotein B (apoB) gene. The identification of individuals with FH has been based on lipid levels and segregation of lipid levels within the family. However, phenotypes are overlapping and family history is not always informative. Therefore, a DNA-based genetic test for FH appears to offer the best alternative. The DNA test gives a simple yes/no answer. The FH test is a definitive tool for the identification of affected family members. The approach of targeted family genetic screening to find new patients is faster and more reliable compared with a biochemical form of screening. Early identification and efficient treatment of such patients is important and highly cost effective. There is evidence to suggest that the nature of the LDL-receptor (LDLR) mutation influences the degree of cholesterol lowering achieved by HMG-CoA reductase inhibitors (statins). The observed differences in the LDL-cholesterol (LDL-C) responses to these drugs among the various LDLR gene mutations are not yet completely understood. The relationships shown between LDLR mutation types and lipid levels, and the response of lipid levels to HMG-CoA reductase inhibitor treatment, will have to be investigated within the framework of pharmacogenetic studies. The variables, which are important in determining the overall atherosclerosis risk, are the result of combined activity in a dynamic network of numerous genes and environment. Candidate genes for atherosclerosis need to be further tested and validated. Future research should be directed at determining the significance of such targets, which patients with FH are at particularly high risk of premature cardiovascular disease, and which environmental factors are effective in modulating this risk. Genetics-based diagnostics will complement identification of FH while improving cardiovascular risk prediction, prevention of disease and treatment efficacy.

Familial hypercholesterolemia--improving treatment and meeting guidelines

Familial hypercholesterolemia (FH) is a common, inherited disorder that affects around one in 500 individuals in the heterozygous form. By the year 2001, more people in the US had FH than were infected by the human immunodeficiency virus. The disease is caused by mutations within the low-density lipoprotein (LDL) receptor gene. FH is associated with elevated plasma LDL-cholesterol (LDL-C) levels, xanthomatosis, early onset of atherosclerosis and premature cardiac death. Patients with heterozygous FH commonly have plasma LDL-C levels that are two-fold higher than normal, while homozygotes have four- to five-fold elevations in plasma LDL-C. Although FH patients have a high risk of developing premature coronary heart disease (CHD), they remain underdiagnosed and undertreated. Early detection of FH is critical to prolonging the life of these patients. Once identified, patients with heterozygous FH can be placed on a diet and drug management program. As the most efficacious and well-tolerated agents, hydroxy methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are usually the drugs of first choice; bile acid sequestrants, niacin, and occasionally fibrates may be used as supplemental agents. Statins may also provide a realistic option for the treatment of some FH homozygotes with genes that produce partially functional LDL receptors. However, a number of patients are still failing to reach treatment guidelines even with the most effective of the currently available statins. The development of new more efficacious statins or the use of new combination therapies such as statins with the cholesterol absorption inhibitor, ezetimibe may help to reduce the current problem of undertreatment in FH patients.

A review on the diagnosis, natural history, and treatment of familial hypercholesterolaemia

BACKGROUND

Familial hypercholesterolaemia (FH) affects approximately 1 in 500 people (10 million world-wide) and the elevated serum cholesterol concentrations lead to a more than 50% risk of fatal or non-fatal coronary heart disease by age 50 years in men and at least 30% in women aged 60 years. Based on a systematic literature search, we review the natural history of FH, describe the diagnostic criteria, and consider the effectiveness of treatment.

METHODS

A comprehensive review was conducted of the literature on the diagnosis of FH, the morbidity and mortality related to treated and untreated FH, and the evidence on the effectiveness of treatment of FH in adults and children. Treatment options have changed since statin treatment became available, and we have not considered pre-statin therapy studies of treatment effectiveness.

FINDINGS AND DISCUSSION

A clinical diagnosis of FH is widely used, but a definitive diagnosis can be made by genetic screening, although mutations are currently only detected in 30-50% of patients with a clinical diagnosis. Under-diagnosis of FH has been reported world-wide ranging from less than 1% to 44%. The relative risk of death of FH patients not treated with statins is between three and fourfold but treatment is effective, and delays or prevents the onset of coronary heart disease. Early detection and treatment is important. Aggressive LDL therapy is more effective in the regression of the carotid intima media thickness than conventional LDL therapy. Diagnosis at birth is problematic, and should be delayed until at least 2 years of age. Statins are not generally recommended for the treatment of children up to adolescence. Resins may be used but poor adherence is a problem. Technical advances in mutation detection, and the identification of other genes that cause FH, are likely to have important implications for the cost effectiveness of genetic diagnosis of FH.

Managing the high-risk patient: therapeutic approaches in 2002

Populations of patients at high risk of coronary heart disease (CHD) include those with type 2 diabetes and those with heterozygous familial hypercholesterolemia (HeFH). Despite benefits of statin lipid-lowering therapy in reducing CHD risk in diabetic patients, screening for dyslipidemia in such patients is inadequate, and patients frequently fail to achieve recommended low-density lipoprotein goals. Diagnosis of HeFH is also suboptimal, despite the reliability of family lipid screening in confirming clinical diagnosis and utility of screening in identifying other family members who are at risk. Patients with HeFH frequently require large reductions in low-density lipoprotein (LDL) cholesterol to achieve target levels. In both of these populations, statins that produce large reductions in LDL cholesterol offer advantages in achieving lipid-lowering goals and in simplifying medical therapy to reduce CHD risk.

Family history assessment: strategies for prevention of cardiovascular disease

Family history assessment can be used to combine population-wide health promotion and risk-reduction efforts with a high-risk, targeted approach to help reduce the burden of cardiovascular disease (CVD). Family history is an independent predictor of CVD, and the upper portion of the family history distribution explains a larger fraction of CVD in the population than can be explained by extreme values of other risk factors (e.g., blood pressure and cholesterol). A positive family history of disease captures the underlying complexities of gene-gene and gene-environment interactions by identifying families with combinations of risk factors, both measured and unmeasured, that lead to disease expression. Family history is a useful tool for identifying most prevalent cases of CVD and for population-wide disease-prevention efforts. A positive family history also identifies the relatively small subset of families in the population at highest risk for CVD who may benefit most from targeted screening and intensive intervention.