Familial Hypercholesterolemia Probands Research Articles

Abstract 4120312: Patient Perspectives on Barriers and Facilitators to Familial Hypercholesterolemia Cascade Testing Through the Lens of the Socio-Ecological Model

Background: Low uptake of Familial Hypercholesterolemia (FH) cascade testing, the stepwise identification of at-risk relatives, leads to missed opportunities for atherosclerotic cardiovascular disease (ASCVD) prevention. The IMPACT-FH study offered strategies (packet, chatbot, and direct contact) to support FH cascade testing. Hypothesis: We hypothesized that IMPACT-FH strategies would facilitate cascade testing uptake and overcome persistent barriers to cascade testing. Aim: We aimed to understand barriers and facilitators to FH cascade testing in the context of the socio-ecological model (SEM) which provides a framework to examine the interconnected influences of intrapersonal, interpersonal, institutional, community, and policy levels. Methods: Semi-structured interviews were conducted with IMPACT-FH study participants. The SEM informed qualitative analysis to identify barriers and facilitators to FH cascade testing. Results: A total of 15 FH probands (initial family member tested) and 12 relatives were interviewed, of whom the majority (59%) were female with an average age of 55.7 years. All relatives completed cascade testing. At the interpersonal level, probands reported that relatives’ attitudes about high cholesterol, including seriousness and treatability, were a barrier or facilitator to cascade testing. Probands explained how relatives’ beliefs were informed by interactions with their clinicians and societal beliefs about cholesterol (i.e., medication stigma). Interpersonally, probands described challenges overcoming relatives’ beliefs and a reluctance to encourage relatives to complete testing despite the availability of novel strategies. Probands and relatives reported that insurance policies and concerns about testing costs informed cascade testing decision-making. Institutional strategies to provide low-cost testing and cost transparency were described as facilitators. Variable access to clinicians with genetics expertise and licensure laws were described as barriers by out-of-state relatives. Probands and relatives agreed that strategies providing direct access genetics expertise (i.e., direct contact, chatbot) helped address these barriers. Conclusion: The IMPACT-FH study ameliorated barriers at higher levels of the SEM related to access to genetics expertise and cost. Intra- and interpersonal barriers remained challenging to overcome. To improve FH detection and ASCVD prevention, it is important to address barriers at all levels of the SEM.

Identification of a novel LDLR p.Glu179Met variant in Thai families with familial hypercholesterolemia and response to treatment with PCSK9 inhibitor

Familial hypercholesterolemia (FH) is a genetic disease characterized by elevated LDL-C levels. In this study, two FH probands and 9 family members from two families from northeastern Thailand were tested for LDLR, APOB, and PCSK9 variants by whole-exome sequencing, PCR-HRM, and Sanger sequencing. In silico analysis of LDLR was performed to analyse its structure‒function relationship. A novel variant of LDLR (c.535_536delinsAT, p.Glu179Met) was detected in proband 1 and proband 2 in homozygous and heterozygous forms, respectively. A total of 6 of 9 family members were heterozygous for LDLR p.Glu179Met variant. Compared with proband 2, proband 1 had higher baseline TC and LDL-C levels and a poorer response to lipid-lowering therapy combined with a PCSK9 inhibitor. Multiple sequence alignment showed that LDLR p.Glu179Met was located in a fully conserved region. Homology modelling demonstrated that LDLR p.Glu179Met variant lost one H-bond and a negative charge. In conclusion, a novel LDLR p.Glu179Met variant was identified for the first time in Thai FH patients. This was also the first report of homozygous FH patient in Thailand. Our findings may expand the knowledge of FH-causing variants in Thai population, which is beneficial for cascade screening, genetic counselling, and FH management to prevent coronary artery disease.

A pragmatic clinical trial of cascade testing for familial hypercholesterolemia

We compared new cases detected per index case in familial hypercholesterolemia (FH) families with or without an identifiable monogenic etiology. We enrolled 52 FH probands with a pathogenic variant (FHg+) in LDLR, APOB, or PCSK9 and 73 probands without such a variant (FHg-). After direct contact by the study team, family members (FMs) of FHg+ probands could opt-in for genetic testing and FMs of FHg- probands were asked to provide a lipid profile. New cases were defined as presence of a pathogenic variant in FHg+ families and as low-density lipoprotein cholesterol ≥155 mg/dL in FHg- families. Of 71 FHg+ probands seen by a genetic counselor, 52 consented and identified 253 FMs (111 consented and were tested, yielding 48 new cases). Of 101 FHg- probands who received counseling, 73 consented and identified 295 FMs (63 consented and were tested, yielding 17 new cases). New case detection per index case was significantly greater in FHg+ than in FHg- families (0.92 vs 0.23), a result of higher cascade testing uptake (43.9 vs 21.4%) and yield (43.2 vs 27.0%) in the former. New case detection rate was significantly higher in FH families with a monogenic etiology than in those without such an etiology owing to greater uptake and yield of cascade testing.

Web-Based Tool (FH Family Share) to Increase Uptake of Cascade Testing for Familial Hypercholesterolemia: Development and Evaluation.

BackgroundFamilial hypercholesterolemia, a prevalent genetic disorder, remains significantly underdiagnosed in the United States. Cascade testing, wherein individuals diagnosed with familial hypercholesterolemia— probands—contact their family members to inform them of their risk for familial hypercholesterolemia, has low uptake in the United States. Digital tools are needed to facilitate communication between familial hypercholesterolemia probands and their family members and to promote sharing of familial hypercholesterolemia–related risk information.ObjectiveWe aimed to create and evaluate a web-based tool designed to enhance familial communication and promote cascade testing for familial hypercholesterolemia.MethodsA hybrid type 1 implementation science framework and a user-centered design process were used to develop an interactive web-based tool—FH Family Share—that enables familial hypercholesterolemia probands to communicate information about their familial hypercholesterolemia diagnosis with at-risk relatives. Probands can also use the tool to draw a family pedigree and learn more about familial hypercholesterolemia through education modules and curated knowledge resources. Usability guidelines and standards were taken into account during the design and development of the tool. The initial prototype underwent a cognitive walkthrough, which was followed by usability testing with key stakeholders including genetic counselors and patients with familial hypercholesterolemia. Participants navigated the prototype using the think-aloud technique, and their feedback was used to refine features of the tool.ResultsKey themes that emerged from the cognitive walkthrough were design, format, navigation, terminology, instructions, and learnability. Expert feedback from the cognitive walkthrough resulted in a rebuild of the web-based tool to align it with institutional standards. Usability testing with genetic counselors and patients with familial hypercholesterolemia provided insights on user experience, satisfaction and interface design and highlighted specific modifications that were made to refine the features of FH Family Share. Genetic counselors and patients with familial hypercholesterolemia suggested inclusion of the following features in the web-based tool: (1) a letter-to-family-member email template, (2) education modules, and (3) knowledge resources. Surveys revealed that 6 of 9 (67%) genetic counselors found information within FH Family Share very easy to find, and 5 of 9 (56%) genetic counselors found information very easy to understand; 5 of 9 (56%) patients found information very easy to find within the website, and 7 of 9 (78%) patients found information very easy to understand. All genetic counselors and patients indicated that FH Family Share was a resource worth returning to.ConclusionsFH Family Share facilitates communication between probands and their relatives. Once informed, at-risk family members have the option to seek testing and treatment for familial hypercholesterolemia.

Severely affected familial hypercholesterolaemia patients with double and triple heterozygous mutations of candidate genes

Background and Aims: Familial hypercholesterolemia (FH) is one of the most frequent diseases with monogenic inheritance caused by various mutations in the genes encoding the low-density lipoprotein (LDL) receptor (LDLR), apolipoprotein (Apo) B100, the proprotein convertase subtilisin/kexin type 9 (PCSK9) and signal-transducing adaptor family member 1 (STAP1). We present three cases of a severely affected FH probands with double and triple heterozygous mutations of these candidate genes.

Targeted Genetic Analysis in a Chinese Cohort of 208 Patients Related to Familial Hypercholesterolemia.

Aim: Familial hypercholesterolemia (FH) is the most commonly encountered genetic condition that predisposes individuals to severe autosomal dominant lipid metabolism dysfunction. Although more than 75% of the European population has been scrutinized for FH-causing mutations, the genetic diagnosis proportion among Chinese people remains very low (less than 0.5%). The aim of this study was to identify genetic mutations and help make a precise diagnosis in Chinese FH patients.Methods: We designed a gene panel containing 20 genes responsible for FH and tested 208 unrelated Chinese possible/probable or definite FH probands. In addition, we called LDLR copy number variation (CNVs) with the panel data by panelcn.MOPS, and multiple ligation-dependent probe amplification (MLPA) was used to search for CNVs in LDLR, APOB, and PCSK9.Results: A total of 79 probands (38.0%) tested positive for a (likely) pathogenic mutation, most of which were LDLR mutations, and three LDLR CNVs called from the panel data were all successfully confirmed by MLPA analysis. In total, 48 different mutations were identified, including 45 LDLR mutations, 1 APOB mutation, 1 ABCG5 mutation, and 1 APOE mutation. Among them, the five most frequent mutations (LDLR c.1879G>A, c.1747C>T, c.313+1G>A, c.400T>C, and APOB c.10579C>T) were detected. Moreover, we also found that patients with LDLR variants of CNVs and splicing and nonsense had increased low-density lipoprotein cholesterol levels when compared with those who carried missense variants.Conclusions: The spectrum of FH-causing mutations in the Chinese population is refined and expanded. Analyses of FH causal genes have been a great help in clinical diagnosis and have deep implications in disease treatment. These data can serve as a considerable dataset for next-generation sequencing analysis of the Chinese population with FH and contribute to the genetic diagnosis and counseling of FH patients.

Lessening the Burden of Familial Hypercholesterolemia Using Health Information Technology.

Despite advances in our understanding of heritable lipid disorders and the availability of highly effective lipid-lowering drugs, the awareness, detection, and control of familial hypercholesterolemia (FH) remain suboptimal. 1 A major reason for the low detection rate in the United States is the lack of a widely accepted screening strategy, despite the recommendations for universal or targeted lipid screening by several expert panels. Although the use of universal lipid screening remains a matter of debate, cascade screening (a form of targeted screening of family members of affected individuals) is acknowledged as the most cost-effective screening strategy for FH. In the Netherlands >26 000 new cases were identified over 2 decades by genotyping family members of FH probands, and it is estimated that genetic cascade screening, coupled with statin therapy for diagnosed patients, could save $92 million per year in the European Union. 1 Several factors lead to the low rates of cascade screening for FH in the United States. First, no nationwide strategy for the early detection of FH exists. Second, the low acceptance of genetic testing for FH in the United States is an impediment to unambiguous diagnosis and cascade screening. Third, patients and family members are often concerned about the stigma associated with genetic diagnoses. Fourth, because of the Health Insurance Portability and Accountability Act, disclosing the risk of genetic disease to family members can incur liability, even if this knowledge leads to early detection and treatment. Fifth, …

Detection of common sequence variations of familial hypercholesterolemia in Taiwan using DNA mass spectrometry

Familial hypercholesterolemia (FH) is a heterogeneous autosomal dominant disease. The genetic heterogeneity of FH requires low-cost, high-throughput, and rapid mutation detection technology to efficiently integrate genetic screening into clinical practice. The aims of the study were to customize the MassARRAY assay to (1) establish an FH mutation assay panel, comprising known point mutations located on FH-causing genes and (2) test the feasibility of the assay for screening FH patients residing in Taiwan who fit the clinical criteria of FH diagnosis. We designed a custom Agena iPLEX assay to detect 68 point mutations on FH-causing genes. First, the assay performance was verified by analyzing 180 previously sequenced subjects (120 with point mutations and 60 healthy controls), with the results being compared with those of Sanger DNA sequencing. Second, a blind study was carried out on 185 FH probands (44 definite FH and 141 probable/possible FH). In the first part of this study, only 1 discrepancy was found between the Agena iPLEX and Sanger sequencing genotyping results. In the blind study, a total of 62 probands with mutations were identified by both techniques. Five mutations were detected by Sanger sequencing assay only. The detection sensitivity and specificity rates of Agena iPLEX were 92.5% and 100%, respectively, in the blind study. The hands-on time for the Agena iPLEX assay was around 1day. The custom-designed Agena iPLEX assay has high specificity and sensitivity for FH genetic screening. Considering its low cost, rapidity, and flexibility, the assay has great potential to be incorporated into FH screening in Taiwan.

790 DIABETES: THE MAIN PREDICTOR OF EXTENSIVE CORONARY CALCIFICATION IN STABLE ANGINA?

In a genetically heterogeneous group of 109 patients with a clinical diagnosis of heterozygous familial hypercholesterolaemia (FH), the influence of gender, apolipoprotein (apo) E genotype and the type of molecular defect in the LDL-receptor (LDLR) gene on the reduction of plasma LDL-cholesterol levels to treatment with a HMG-CoA reductase inhibitor (simvastatin) were studied. Response was determined as the percentage fall in LDL-cholesterol from untreated levels and as the proportion of patients where levels fell below 4.9 or 4.1 mmol/l. Of the patients, 86 individuals had tendon xanthomata (TX+) and a diagnosis of ‘definite’ FH and these individuals presented with a significantly higher untreated LDL-cholesterol compared to the 23 individuals who did not have xanthomas (TX−) and a diagnosis of ‘probable’ FH (8.14±0.19 vs. 6.81±0.25, P=0.001). Overall, HMG-CoA reductase inhibitor doses of 10, 20 or 40 mg/day resulted in a significant fall of LDL-cholesterol levels of 29, 39 and 49%, but at all doses those with TX had significantly higher levels than those without, and significantly fewer TX+ patients achieved LDL-cholesterol levels below 4.9 or 4.1 mmol/l than the TX− group (P<0.05 at each dose). In the TX+ group the response to treatment was of similar magnitude in men and women and in patients with different apoE genotype. In the ‘probable’ FH probands only three mutations were identified (detection rate 13%), one in the LDLR gene and two in the APOB gene, a detection rate significantly lower (P=0.02) than in the ‘definite’ FH probands where 28 mutations were detected (detection rate 37%). In the TX+ patients where no mutation was detected, treatment resulted in a greater proportion achieving LDL-cholesterol levels below 4.9 and 4.1 mmol/l compared to those with any LDLR mutation, this difference was close to statistical significance at the 4.9 mmol/l threshold at 10 mg/day (41 vs. 13%, P=0.058). For the 14 patients with an LDLR mutation that was predicted to be ‘severe’, fewer achieved LDL-cholesterol levels below 4.9 or 4.1 mmol/l at each dosage compared to the 16 individuals with ‘mild’ mutations, and this difference was statistically significant at the maximal dosage of 40 mg/day (P=0.018). Thus although characterisation of the molecular defect in FH patients may not be relevant to their immediate clinical management, those with a particular mutation may need more aggressive lipid-lowering treatment to reach LDL-cholesterol levels recommended to reduce the risk of coronary heart disease (CHD).

Analysis of Sequence Variations in the LDL Receptor Gene in Spain: General Gene Screening or Search for Specific Alterations?

Familial hypercholesterolemia (FH) is a frequent form of autosomal-dominant hypercholesterolemia that predisposes to premature coronary atherosclerosis. FH is caused by sequence variations in the gene coding for the LDL receptor (LDLR). This gene has a wide spectrum of sequence variations, and genetic diagnosis can be performed by 2 strategies. Point variations and large rearrangements were screened along all the LDLR gene (promoter, exons, and flanking intron sequences). We screened a sample of 129 FH probands from the Valencian Community, Spain, and identified 54 different LDLR sequence variations. The most frequent (10% of cases) was 111insA, and 60% of the variants had a frequency as low as 1%. A previously described method for detection of known sequence variations in the Spanish population by DNA array analysis allowed the identification of only approximately 50% of patients with a variant LDLR gene and approximately 40% of the screened samples. Our results indicate that the adequate procedure to identify LDLR sequence variations in outbreed populations should include screening of the entire gene.

FH clinical phenotype in Greek patients with LDL-R defective vs. negative mutations.

Familial hypercholesterolaemia (FH) is caused by mutations in the low-density lipoprotein receptor gene and the gene encoding apolipoprotein B-100, affecting one in 500 individuals. One hundred and eighty-three Greek FH patients were screened for mutations on the LDLR and ApoB genes. We identified mutations in 67 probands and 11 relatives. Sixteen mutations located in eight different exons and the promoter of the LDLR were discovered. Among them 10 were missense mutations (C6W, S265R, A370T, Q363P, D365E, V408M, A410T, A517T, G528D, G571E), two were nonsense mutations (Q363X and C660X), three were splice defects (2140 + 5G-->A and 2140 + 9C-->T, 1706 - 10G-->A), and one was a nucleotide substitution (- 45delT) on the promoter. None of the subjects carried any apoB mutation. The detection rate of mutations in this study was 43%. From the above mutations, A410T, A519T and the splice site defects 2140 + 9C-->T were detected for the first time in the Greek population. Among them V408M, G528D, C6W and S265R account for 73% of heterozygous FH probands. V408M mutation is more common in Central West, while C6W is more common in Central East. Separating the patients into two groups (receptor defective and receptor negative) we found that the receptor negative group had higher levels of total cholesterol, low-density lipoprotein cholesterol and higher prevalence of tendon xanthomas compared with the receptor-defective group. The homogenous molecular basis of familial hypercholesterolaemia in Greece facilitates the application of a DNA diagnostic strategy based on the origin of the patient. The early mutation analysis would add valuable information on the severity of the disease.

Familial Hypercholesterolemia Due to Ligand-Defective Apolipoprotein B100.: First Case Report in a Mexican Family

Background Familial defective apolipoprotein B100 (FDB) is one of the known causes of familial hypercholesterolemia (FH). Its frequency among subjects with FH varies among ethnic groups; information on FH is insufficient for populations from Latin America. We proposed to describe prevalence of FDB in a cohort of Mexican FH probands ( n = 30). Methods We searched for the known FDB mutations using polymerase chain reaction assays. In this set of patients, mean lipid values were representative of FH (cholesterol 351 mg/dL, LDL cholesterol 274 mg/dL, HDL cholesterol 51 mg/dL, and triglycerides 132 mg/dL). Results One subject with Arg3500Gln mutation was found: a 44-year-old male with a history of coronary heart disease (CHD) among paternal relatives. His lipid profile was cholesterol 370 mg/dL, LDL-cholesterol 300 mg/dL, HDL-cholesterol 32 mg/dL, and triglycerides 189 mg/dL. Tendinous xanthomata were detected. Three of four siblings, one of three sons, and one of nine nieces and nephews carried the mutation. The mutation was confirmed by automated sequencing. Tendinous xanthomata were absent in affected subjects younger than age 20 years; additionally, the subjects had borderline cholesterol levels. Conclusions Our data suggest that FDB explains the small number of FH cases in Mexico. Inclusion of molecular biology assays to the clinical laboratory makes it possible to diagnose affected individuals with borderline cholesterol levels or without tendinous xanthomata.

Results from a family and DNA based active identification programme for familial hypercholesterolaemia

Heterozygous familial hypercholesterolaemia (FH) is a common inborn error of lipoprotein metabolism, which strongly predisposes for coronary artery disease and premature cardiac death.1 In 1994, a family based active identification...

Frequency of the R3500Q mutation of the apolipoprotein B-100 gene in a sample screened clinically for familial hypercholesterolemia in Hungary

Familial hypercholesterolemia (FH) and familial defective apolipoprotein B-100 (FDB) cause early onset of coronary heart diseases (CHD). According to the recommendations of the international MEDPED program, we tried to find FH cases. We analyzed 73 FH probands and their 304 first-degree relatives. A total of 39 probands were found from the 21 000 subjects screened (1:538) from family doctors’ registers recording all citizens, while the remaining 34 were derived from screened patients from lipid clinics. In our FH probands, four cases of FDB (R3500Q mutation) were diagnosed with allele-specific PCR, and the mutation was also detectable in five cases out of seven living family members. In the remaining 69 FH families, 156 people were diagnosed clinically with FH, and 31.8% of the males (against 13% of the not clinically diagnosed FH males, P<0.01), and 32.4% of the females (against 13.5% of the not clinically diagnosed FH females, P<0.01) suffered from early onset CHD. The plasma total cholesterol level of the FDB patients, especially in the younger patients, was very close to normal values. Therefore, the FDB patients seem to be under-represented in this type of survey. Because FDB is one of the independent causes of early onset CHD, the R3500Q mutation should be considered in families with a high frequency of cardiovascular diseases.

Polymorphisms of the low-density lipoprotein receptor gene in Brazilian individuals with heterozygous familial hypercholesterolemia.

Familial hypercholesterolemia (FH) is a metabolic disorder inherited as an autosomal dominant trait characterized by an increased plasma low-density lipoprotein (LDL) level. The disease is caused by several different mutations in the LDL receptor gene. Although early identification of individuals carrying the defective gene could be useful in reducing the risk of atherosclerosis and myocardial infarction, the techniques available for determining the number of the functional LDL receptor molecules are difficult to carry out and expensive. Polymorphisms associated with this gene may be used for unequivocal diagnosis of FH in several populations. The aim of our study was to evaluate the genotype distribution and relative allele frequencies of three polymorphisms of the LDL receptor gene, HincII(1773) (exon 12), AvaII (exon 13) and PvuII (intron 15), in 50 unrelated Brazilian individuals with a diagnosis of heterozygous FH and in 130 normolipidemic controls. Genomic DNA was extracted from blood leukocytes by a modified salting-out method. The polymorphisms were detected by PCR-RFLP. The FH subjects showed a higher frequency of A+A+ (AvaII), H+H+ (HincII(1773)) and P1P1 (PvuII) homozygous genotypes when compared to the control group (P<0.05). In addition, FH probands presented a high frequency of A+ (0.58), H+ (0.61) and P1 (0.78) alleles when compared to normolipidemic individuals (0.45, 0.45 and 0.64, respectively). The strong association observed between these alleles and FH suggests that AvaII, HincII(1773) and PvuII polymorphisms could be useful to monitor the inheritance of FH in Brazilian families.

The type of mutation in the low density lipoprotein receptor gene influences the cholesterol-lowering response of the HMG-CoA reductase inhibitor simvastatin in patients with heterozygous familial hypercholesterolaemia

In a genetically heterogeneous group of 109 patients with a clinical diagnosis of heterozygous familial hypercholesterolaemia (FH), the influence of gender, apolipoprotein (apo) E genotype and the type of molecular defect in the LDL-receptor (LDLR) gene on the reduction of plasma LDL-cholesterol levels to treatment with a HMG-CoA reductase inhibitor (simvastatin) were studied. Response was determined as the percentage fall in LDL-cholesterol from untreated levels and as the proportion of patients where levels fell below 4.9 or 4.1 mmol/l. Of the patients, 86 individuals had tendon xanthomata (TX+) and a diagnosis of ‘definite’ FH and these individuals presented with a significantly higher untreated LDL-cholesterol compared to the 23 individuals who did not have xanthomas (TX−) and a diagnosis of ‘probable’ FH (8.14±0.19 vs. 6.81±0.25, P=0.001). Overall, HMG-CoA reductase inhibitor doses of 10, 20 or 40 mg/day resulted in a significant fall of LDL-cholesterol levels of 29, 39 and 49%, but at all doses those with TX had significantly higher levels than those without, and significantly fewer TX+ patients achieved LDL-cholesterol levels below 4.9 or 4.1 mmol/l than the TX− group ( P<0.05 at each dose). In the TX+ group the response to treatment was of similar magnitude in men and women and in patients with different apoE genotype. In the ‘probable’ FH probands only three mutations were identified (detection rate 13%), one in the LDLR gene and two in the APOB gene, a detection rate significantly lower ( P=0.02) than in the ‘definite’ FH probands where 28 mutations were detected (detection rate 37%). In the TX+ patients where no mutation was detected, treatment resulted in a greater proportion achieving LDL-cholesterol levels below 4.9 and 4.1 mmol/l compared to those with any LDLR mutation, this difference was close to statistical significance at the 4.9 mmol/l threshold at 10 mg/day (41 vs. 13%, P=0.058). For the 14 patients with an LDLR mutation that was predicted to be ‘severe’, fewer achieved LDL-cholesterol levels below 4.9 or 4.1 mmol/l at each dosage compared to the 16 individuals with ‘mild’ mutations, and this difference was statistically significant at the maximal dosage of 40 mg/day ( P=0.018). Thus although characterisation of the molecular defect in FH patients may not be relevant to their immediate clinical management, those with a particular mutation may need more aggressive lipid-lowering treatment to reach LDL-cholesterol levels recommended to reduce the risk of coronary heart disease (CHD).

Identification of a common low density lipoprotein receptor mutation (C163Y) in the west of Scotland.

Familial hypercholesterolaemia (FH) is an autosomal codominant disorder characterised by high levels of LDL cholesterol and a high incidence of coronary artery disease. Our aims were to track the low...

Development of a microsatellite-based approach to co-segregation analysis of familial hypercholesterolaemic kindreds.

Co-segregation studies based on a selection of intragenic restriction fragment length polymorphisms of the low density lipoprotein receptor (LDLR) gene have been used extensively both for research and diagnostic studies of familial hypercholesterolaemia (FH) families, because direct mutation screening remains complex. Here we describe the development and application of a more efficient approach to co-segregation studies based on highly informative dinucleotide and tetranucleotide repeats flanking the LDLR gene. A series of microsatellites (D19S391, D19S394, D19S221 and D19S179) were selected for study on the basis of linkage analysis in the CEPH families using intragenic polymorphisms for a TA repeat (exon 18) in the LDLR gene, and earlier data for a Pvu II polymorphism (intron 15). A physical map of the region of chromosome 19 also contributed to this selection. One marker in particular, D19S394, sited 150 kilobases telomeric to the gene, was extremely useful, displaying 90% heterozygosity, robust PCR of tetranucleotide repeats without stutter bands, and no recombination with the LDLR gene (theta = 0, LOD 68). Use of this marker in the families of twenty-three FH probands from Hampshire demonstrated co-segregation of the hyperlipidaemia phenotype with the LDLR gene region, except in one family with defective apolipoprotein B-100, and a family turning out to display familial combined hyperlipidaemia. This approach should facilitate the search for any families where FH does not co-segregate with the LDLR gene, and will enhance the repertoire of molecular diagnostic tools available for FH.

Lp(a) levels in Greek patients with heterozygous familial hypercholesterolemia

We undertook the present study to evaluate the lipid profile in 82 (51 male, 31 female) Greek individuals with heterozygous familial hypercholesterolemia (FH), aged 13–61 years from 22 families. FH heterozygotes had significantly elevated serum Lp(a) levels in comparison with 82 normal controls. Serum Lp(a) levels were also increased in FH probands compared to their controls. Additionally, serum Lp(a) concentration was elevated in the FH heterozygotes compared to their unaffected first degree relatives.

The Trp 23-Stop and Trp 66-Gly mutations in the LDL receptor gene: common causes of familial hypercholesterolemia in Denmark

Mutations in the gene for the low density lipoprotein (LDL) receptor cause the autosomal dominant disease familial hypercholesterolemia (FH), the prevalence of which is about 0.2% in most populations. By PCR-SSCP analysis and direct sequencing, we identified the receptor-negative Trp 23-Stop LDL receptor mutation (FH Cincinnati-5) in 10 of 63 FH probands and the receptor-defective Trp 66-Gly LDL receptor mutation (FH French Canadian-4) in another 10 of the 63 FH probands. These two mutations thus account for 30% of diagnosed FH families in Denmark. Comparison of the mean lipid concentrations (unadjusted and adjusted for age), including serum total cholesterol and LDL-cholesterol, showed no significant differences between the two groups of FH heterozygote probands (cholesterol: 10.7 mmol/l vs. 10.7 mmol/l) and between the probands and 16 and 22 non-proband family members with the Trp 23-stop (cholesterol: 10.1 mmol/l) and Trp 66-Gly (cholesterol: 10.7 mmol/l) mutations, respectively.