Genotype-phenotype correlation in a large cohort of pediatric patients with heterozygous and homozygous familial hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated low-density lipoprotein cholesterol (LDL-C) levels and premature cardiovascular disease (CVD). Both the heterozygous form and the very severe homozygous form can be diagnosed by genetic testing and by clinical criteria. Genetic testing can discern FH in a form caused by complete absence of the LDL-receptors, the negative variant and a form leading to reduced activity of the LDL receptors, the defective variant. The aim of this study is to provide more insight in the genotype-phenotype correlation in children and adolescents diagnosed with heterozygous FH (HeFH) and with homozygous FH (HoFH), specifically in relation to the clinical and therapeutic consequences of the negative and defective variant of FH. METHODS AND RESULTS: Data of 5904 children with a tentative diagnosis of FH referred to our center for genetic testing were collected. A lipid-profile was present in 3494 children, who became the study cohort. In this large cohort of children, which includes 2714 HeFH and 41 HoFH patients, it is shown that receptor negative variants are associated with significant higher LDL-C levels in HeFH patients than receptor defective variants (6.0 versus 4.9 mmol/L; p  < 0.001). A negative/negative variant is associated with a significant higher LDL-C level jn HoFH patients than a negative/defective variant, which in itself has a higher LDL-C level than a defective/defective variant. Significantly more premature CVD is present in close relatives of children with HeFH with negative variants compared to close relatives of HeFH children with defective variants (75% vs 59%; p  < 0.001). CONCLUSIONS: Performing genetic testing and identifying the type of underlying genetic variant is of added value in order to distinguish between pediatric patients with higher risks of premature CVD and to identify those that will benefit most from new types of lipid-lowering therapies. Since in children the phenotype of FH is less affected by environmental factors, the study substantiates the genotype-phenotype correlation in this large pediatric population.

Mutations in LPL, APOC2, APOA5, GPIHBP1 and LMF1 in patients with severe hypertriglyceridaemia.

OBJECTIVES: The severe forms of hypertriglyceridaemia (HTG) are caused by mutations in genes that lead to the loss of function of lipoprotein lipase (LPL). In most patients with severe HTG (TG > 10 mmol L(-1) ), it is a challenge to define the underlying cause. We investigated the molecular basis of severe HTG in patients referred to the Lipid Clinic at the Academic Medical Center Amsterdam. METHODS: The coding regions of LPL, APOC2, APOA5 and two novel genes, lipase maturation factor 1 (LMF1) and GPI-anchored high-density lipoprotein (HDL)-binding protein 1 (GPIHBP1), were sequenced in 86 patients with type 1 and type 5 HTG and 327 controls. RESULTS: In 46 patients (54%), rare DNA sequence variants were identified, comprising variants in LPL (n = 19), APOC2 (n = 1), APOA5 (n = 2), GPIHBP1 (n = 3) and LMF1 (n = 8). In 22 patients (26%), only common variants in LPL (p.Asp36Asn, p.Asn318Ser and p.Ser474Ter) and APOA5 (p.Ser19Trp) could be identified, whereas no mutations were found in 18 patients (21%). In vitro validation revealed that the mutations in LMF1 were not associated with compromised LPL function. Consistent with this, five of the eight LMF1 variants were also found in controls and therefore cannot account for the observed phenotype. CONCLUSIONS: The prevalence of mutations in LPL was 34% and mostly restricted to patients with type 1 HTG. Mutations in GPIHBP1 (n = 3), APOC2 (n = 1) and APOA5 (n = 2) were rare but the associated clinical phenotype was severe. Routine sequencing of candidate genes in severe HTG has improved our understanding of the molecular basis of this phenotype associated with acute pancreatitis and may help to guide future individualized therapeutic strategies.

Extreme xanthomatosis in patients with both familial hypercholesterolemia and cerebrotendinous xanthomatosis.

Two unrelated individuals were referred to Lipid Clinics in The Netherlands and Chile with extreme xanthomatosis and hypercholesterolemia. Both were diagnosed with heterozygous familial hypercholesterolemia (heFH) after molecular genetic analysis of the low-density lipoprotein (LDL) receptor gene. Since heFH by itself could not account for the massive xanthomas, the presence of an additional hereditary lipid or lipoprotein disorder was suspected. Further genetic analysis revealed homozygozity for mutations in the sterol 27-hydroxylase gene, confirming the diagnosis of cerebrotendinous xanthomatosis (CTX). Markedly, the typical neurological manifestations of CTX were absent, suggestive of a protective role of LDL-receptor deficiency against the severe neurological consequences of CTX.

Founder mutations in the Netherlands: geographical distribution of the most prevalent mutations in the low-density lipoprotein receptor and apolipoprotein B genes.

BACKGROUND: In the Netherlands, a screening programme was set up in 1994 in order to identify all patients with familial hypercholesterolaemia (FH). After 15 years of screening, we evaluated the geographical distribution, possible founder effects and clinical phenotype of the 12 most prevalent FH gene mutations. METHODS: Patients who carried one of the 12 most prevalent mutations, index cases and those identified between 1994 and 2009 through the screening programme and whose postal code was known were included in the study. Low-density lipoprotein cholesterol (LDL-C) levels at the time of screening were retrieved. The prevalence of identified FH patients in each postal code area was calculated and visualised in different maps. RESULTS: A total of 10,889 patients were included in the study. Mean untreated LDL-C levels ranged from 4.4 to 6.4 mmol/l. For almost all mutations, a region of high prevalence could be observed. In total, 51 homozygous patients were identified in the Netherlands, of which 13 true homozygous for one of the 12 most prevalent mutations. The majority of them were living in high-prevalence areas for that specific mutation. CONCLUSIONS: Phenotypes with regard to LDL-C levels varied between the 12 most prevalent FH mutations. For most of these mutations, a founder effect was observed. Our observations can have implications with regard to the efficiency of molecular screening and physician's perception of FH and to the understanding of the prevalence and distribution of homozygous patients in the Netherlands.

Molecular characterization of Polish patients with familial hypercholesterolemia: novel and recurrent LDLR mutations.

Autosomal dominant hypercholesterolemia (ADH) is caused by mutations in the genes coding for the low-density lipoprotein receptor (LDLR), apolipoprotein B-100 (APOB), or proprotein convertase subtilisin/kexin type 9 (PCSK9). In this study, a molecular analysis of LDLR and APOB was performed in a group of 378 unrelated ADH patients, to explore the mutation spectrum that causes hypercholesterolemia in Poland. All patients were clinically diagnosed with ADH according to a uniform protocol and internationally accepted WHO criteria. Mutational analysis included all exons, exon-intron boundaries and the promoter sequence of the LDLR, and a fragment of exon 26 of APOB. Additionally, the MLPA technique was applied to detect rearrangements within LDLR. In total, 100 sequence variations were identified in 234 (62%) patients. Within LDLR, 40 novel and 59 previously described sequence variations were detected. Of the 99 LDLR sequence variations, 71 may be pathogenic mutations. The most frequent LDLR alteration was a point mutation p.G592E detected in 38 (10%) patients, followed by duplication of exons 4-8 found in 16 individuals (4.2%). Twenty-five cases (6.6%) demonstrated the p.R3527Q mutation of APOB. Our findings imply that major rearrangements of the LDLR gene as well as 2 point mutations (p.G592E in LDLR and p.R3527Q in APOB) are frequent causes of ADH in Poland. However, the heterogeneity of LDLR mutations detected in the studied group confirms the requirement for complex molecular studies of Polish ADH patients.

Silent exonic mutations in the low-density lipoprotein receptor gene that cause familial hypercholesterolemia by affecting mRNA splicing.

In a large group of patients with the clinical phenotype of familial hypercholesterolemia, such as elevated low-density lipoprotein (LDL) cholesterol and premature atherosclerosis, but without functional mutations in the genes coding for the LDL receptor and apolipoprotein B, we examined the effect of 128 seemingly neutral exonic and intronic DNA variants, discovered by routine sequencing of these genes. Two variants, G186G and R385R, were found to be associated with altered splicing. The nucleotide change leading to G186G resulted in the generation of new 3'-splice donor site in exon 4 and R385R was associated with a new 5'-splice acceptor site in exon 9 of the LDL receptor gene. Splicing of these alternate splice sites leads to an in-frame 75-base pair deletion in a stable mRNA of exon 4 in case of G186G and R385R resulted in a 31-base pair frame-shift deletion in exon 9 and non-sense-mediated mRNA decay.

Sib-pair analysis detects elevated Lp(a) levels and large variation of Lp(a) concentration in subjects with familial defective ApoB.

Whether or not Lp(a) plasma levels are affected by the apoB R3500Q mutation, which causes Familial Defective apoB (FDB), is still a matter of debate. We have analyzed 300 family members of 13 unrelated Dutch index patients for the apoB mutation and the apolipoprotein(a) [apo(a)] genotype. Total cholesterol, LDL-cholesterol, and lipoprotein(a) [Lp(a)] concentrations were determined in 85 FDB heterozygotes and 106 non-FDB relatives. Mean LDL levels were significantly elevated in FDB subjects compared to non-FDB relatives (P < 0.001). Median Lp(a) levels were not different between FDB subjects and their non-FDB relatives. In contrast, sib-pair analysis demonstrated a significant effect of the FDB status on Lp(a) levels. In sib pairs identical by descent for apo(a) alleles but discordant for the FDB mutation (n = 11) each sib with FDB had a higher Lp(a) level than the corresponding non-FDB sib. Further, all possible sib pairs (n = 105) were grouped into three categories according to the absence/presence of the apoB R3500Q mutation in one or both subjects of a sib pair. The variability of differences in Lp(a) levels within the sib pairs increased with the number (0, 1, and 2) of FDB subjects present in the sib pair. This suggests that the FDB status increases Lp(a) level and variability, and that apoB may be a variability gene for Lp(a) levels in plasma.

High frequency of APOB gene mutations causing familial hypobetalipoproteinaemia in patients of Dutch and Spanish descent.

BACKGROUND: Familial hypobetalipoproteinaemia (FHBL) is an autosomal co-dominant hereditary disorder of lipoprotein metabolism characterised by decreased low density lipoprotein (LDL) cholesterol and apolipoprotein B (APOB) plasma levels. High levels of plasma APOB and LDL cholesterol are strong predictors for risk of cardiovascular disease (CVD), while individuals with low APOB and LDL cholesterol levels are thought to have lower than average risk for CVD, and in fact, heterozygous FHBL patients appear to be asymptomatic. METHODS: Rather than identifying truncated APOB proteins in plasma fractions separated by gel electrophoresis, which will miss any mutations in proteins smaller than 30 kb, we analysed the APOB gene directly, using PCR. RESULTS: We identified nine different mutations, six of which are novel. Each mutation showed complete co-segregation with the FHBL phenotype in the families, and statistically significant differences between carriers and non-carriers were found for plasma total, LDL, and HDL cholesterol, triglycerides, and APOB levels, but not for APOA1 levels. All carriers of an APOB mutation were completely free from CVD. CONCLUSIONS: Prolonged low levels of LDL cholesterol and elevated levels of HDL cholesterol may reduce the progression of atherosclerotic disease, but this has not been unequivocally shown that this is indeed the case in individuals with FHBL, and is the subject of a current study.

Familial defective apolipoprotein B-100 is clinically indistinguishable from familial hypercholesterolemia.

BACKGROUND: Familial defective apolipoprotein B-100 is caused by a substitution of adenine for guanine in exon 26 of the gene coding for apolipoprotein B, which results in the substitution of glutamine for arginine in the putative low-density lipoprotein-receptor binding domain of the mature protein. This amino acid substitution diminishes the binding capacity of the low-density lipoprotein particle for the low-density lipoprotein receptor, which in turn leads to an increase in levels of plasma total and low-density lipoprotein cholesterol. METHODS: To identify carriers of this mutation by means of molecular biology techniques in a large cohort of Dutch patients living in the Netherlands and in Canada with primary hypercholesterolemia, to establish the frequency of the disorder, and to investigate its clinical signs and symptoms and the response to cholesterol-lowering therapy. RESULTS: A total of 1248 patients were screened, and the mutation was found in 18 patients who were initially all diagnosed as having familial hypercholesterolemia. Ten of 18 patients had tendon xanthomas or an arcus cornealis or both, and eight of 18 patients had angina or other evidence of coronary artery disease. CONCLUSIONS: The disorder was clinically indistinguishable from familial hypercholesterolemia in terms of physical characteristics and lipoprotein measures. Response to lipid-lowering therapy with beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitors was similar to that reported in patients with familial hypercholesterolemia. The mutation was associated with a similar haplotype, which was also reported in other patients of Western European descent with familial defective apolipoprotein B100. This strongly suggests that the mutation has a common chromosomal background that originated in Western Europe.

Genetic linkage of hereditary motor and sensory neuropathy type I (Charcot-Marie-Tooth disease) to markers of chromosomes 1 and 17.

Hereditary motor and sensory neuropathy type 1 (HMSN I) is an autosomal dominant disorder genetically localized on chromosome 1 in a few families and on chromosome 17 in other families. We analyzed linkage between 6 markers of chromosome 1, 2 markers of chromosome 17, and the HMSN I locus using restriction fragment length polymorphisms and serotyping for the Duffy blood group in 5 families with HMSN I. Only in 1 of these families is linkage present between the disease locus and the loci for Duffy blood group and glucocerebrosidase (chromosome 1 markers). In the 4 other families the HMSN I locus is linked to the chromosome 17 markers pEW301 and pA10-41.

Familial hypercholesterolemia. Acceptor splice site (G-->C) mutation in intron 7 of the LDL-R gene: alternate RNA editing causes exon 8 skipping or a premature stop codon in exon 8. LDL-R(Honduras-1) [LDL-R1061(-1) G-->C].

Familial hypercholesterolemia (FH) is an autosomal dominant lipoprotein disorder caused by defects in the low density lipoprotein (LDL) receptor (R) gene. We report a novel mutation of the LDL-R gene in a 38-year-old man with homozygous FH from the province of Trujilo in Northern Honduras. The patient presented with tendinous xanthomas over the extensor tendons as well as xanthelasmas at sites of surgical scars. He was diagnosed with severe coronary artery disease requiring revascularization at age 29. After an unsuccessful course of treatment with simvastatin, the patient has been treated with plasma apheresis and macromolecular plasma filtration bi-monthly. Haplotyping of the LDL-R gene revealed homozygosity for the rare 'J' allele and a loss of the EcoRV restriction cleavage site in exon 8. Single stranded conformational polymorphism of exons 3, 6, 7, 9, 10 and 8 reveals an abnormal migration pattern in exon 8. Direct sequencing of the promoter region, exons 1, 4, 8 and 13 revealed two RFLP's and a novel mutation in intron 7. This mutation consists of G-->C transposition at the acceptor splice site of exon 8 at the last nucleotide of intron 7 [LDL-R1061(-1)G-->C]. Reverse transcriptase (RT) PCR amplification of RNA from monocytes obtained from the patient reveals a decrease in LDL-R mRNA (52% of control) and skipping of exon 8 (approximately 38%, as assessed by densitometric scanning of the amplified fragments) to form a new RNA transcript that includes exons 7 and 9 without frameshift. Alternative RNA editing leads to a new cryptic acceptor splice site 17 bp downstream in exon 8 producing a frameshift mutation and a predicted premature stop codon 1138 bp from the transcriptional start site (approxiamtely 62%). Western blotting analysis using a monoclonal antibody (C7) directed at the amino terminus of the LDL-R protein reveals a marked reduction in LDL-R protein expressed in monocytes obtained from the patient. We conclude that LDL-R1061(-1)G-->C is a novel mutation of the LDL-R gene that results in marked decrease in LDL-R mRNA levels and protein expression by two alternate RNA editing mechanisms, that cause skipping of exon 8 or the use of a novel cryptic acceptor splice site in exon 8 with a frameshift and premature stop codon. The patient continues to do well on selective plasma filtration but developed bilateral severe carotid artery disease requiring surgical intervention.

Differential diagnosis of genetic disease by DNA restriction fragment length polymorphisms.

DNA restriction fragment length polymorphisms (RFLPs) are used for diagnosis of genetic disease in families known to be affected by specific disorders, but RFLPs can be also useful for the differential diagnosis of hereditary disease. An RFLP pattern represents the inheritance of chromosomal markers in a family, and such a pattern may be compatible with the inheritance of a certain disorder in that family. Probabilities to find such a pattern if the disorder were present and if it were absent can be combined with the prior probabilities of disease considered in the differential diagnosis on the basis of previous clinical and laboratory data. Bayes' theorem is used to calculate the posterior probabilities of the diseases in question. This approach is illustrated in a family suffering from either spinal muscular atrophy (an autosomal recessive disease) or Becker muscular dystrophy (an X-chromosomal disorder). Probabilities to exclude a certain disorder can be calculated in advance, as some RFLP patterns are not compatible with the presence of that disorder.

Molecular genetics and gene expression in atherosclerosis.

Although molecular cardiology is a relative young discipline, the impact of the new techniques on diagnosis and therapy in cardiovascular disease are extensive. Our insight into pathophysiological mechanisms is rapidly expanding and is changing our understanding of cardiovascular disease radically and irrevocably. Molecular cardiology has many different aspects. In this paper the importance of molecular cardiology and genetics for every day clinical practice are briefly outlined. It is expected that in the genetic predisposition for atherosclerotic disease multiple genes are involved (genetics). The role of only a minority of genes involved in the atherosclerotic process is known. Far less is known about particular gene-gene and gene-environment interactions. In some families disease can be explained mostly by a single, major gene (monogenic), of which the lipid disorder Familial Hypercholesterolemia is an example. In other cases, one or several variations in minor genes (multigenic) contribute to an atherosclerotic predisposition, for instance the lipoprotein lipase gene. Although mutations in this gene influence lipoprotein levels, disease development is predominantly depending on environmental influences. Recently several additional genetic risk factors were identified including elevated levels of lipoprotein (a) [Lp(a)], the DD genotype of angiotensin converting enzyme (ACE), and elevated levels of homocysteine. This illustrates the complexity of genetics in relation to atherosclerosis and the difficulty to assign predictive values to separate genetic risk factors. Furthermore, little attention has been given to protective genes thus far, explaining why some high risk patients are protected from vascular disease. Genetics based treatment or elimination of the genetic risk factor requires complete understanding of the pathogenic molecular basis. Once this requirement is fulfilled, disease management can be strived for, provided that adequate medical management is available. Recent studies suggest that such treatment should be genotype specific, as the genetic makeup can determine the outcome of a pharmacological intervention (pharmacogenetics). Once the trigger for atherosclerosis has initiated disease development, various genes are activated or silenced and contribute to lesion progression. Every stage of lesion development depends on a different gene expression programme (genomics). In this review paper an introduction is provided into genetics, pharmacogenetics and gene expression with respect to atherosclerotic disease.

Analysis of the Afrikaner mutation in exon 9 of the low-density lipoprotein receptor gene in a large Dutch kindred suffering from familial hypercholesterolaemia.

Familial hypercholesterolaemia (FH) is the most common genetic metabolic disorder, affecting about 1 in 500 persons in the general population. With novel techniques, it is possible to identify the molecular defects underlying FH in the gene coding for the low-density lipoprotein (LDL) receptor, thereby confirming the diagnosis of FH. In this study we present a large family with a specific mutation in exon 9 of the LDL-receptor gene (an Afrikaner mutation) and we demonstrate that by a large-scale case-finding study in this family, carriers of such a mutation can be detected. Of 63 family members, 13 were shown to be at risk for cardiovascular disease as judged by their lipoprotein profile or the presence of the Afrikaner mutation. Two persons were detected, affected with a dyslipidaemia other than FH. Medical management was initiated in order to reduce the high cardiovascular risk associated with this disorder.

Mortality over two centuries in large pedigree with familial hypercholesterolaemia: family tree mortality study.

OBJECTIVE: To estimate all cause mortality from untreated familial hypercholesterolaemia free from selection for coronary artery disease. DESIGN: Family tree mortality study. SETTING: Large pedigree in Netherlands traced back to a single pair of ancestors in the 19th century. SUBJECTS: All members of pedigree aged over 20 years with 0.5 probability of carrying a mutation for familial hypercholesterolaemia. MAIN OUTCOME MEASURE: All cause mortality. RESULTS: A total of 70 deaths took place among 250 people analysed for 6950 person years. Mortality was not increased in carriers of the mutation during the 19th and early 20th century; it rose after 1915, reached its maximum between 1935 and 1964 (standardised mortality ratio 1.78, 95% confidence interval 1.13 to 2.76; P=0.003), and fell thereafter. Mortality differed significantly between two branches of the pedigree (relative risk 3.26, 95% confidence interval 1.74 to 6.11; P=0.001). CONCLUSIONS: Risk of death varies significantly among patients with familial hypercholesterolaemia. This large variability over time and between branches of the pedigree points to a strong interaction with environmental factors. Future research is required to identify patients with familial hypercholesterolaemia who are at extreme risk and need early and vigorous preventive measures.

[Is detection and treatment of familial hypercholesterolemia indicated in children?]. / Is opsporing en behandeling van familiaire hypercholesterolemie geïndiceerd bij kinderen?

Familial hypercholesterolaemia (FH) is a congenital metabolic disorder predisposing to severe atherosclerosis resulting in coronary heart disease sometimes even at early adult age. Children with FH lack the stigmata at physical examination and measuring the cholesterol level does not always enable the clinician to make the diagnosis. In about 70% of the cases, the diagnosis of FH in childhood can be made by means of molecular-biological examination, by demonstrating the underlying defect of the LDL cholesterol receptor gene. In the remaining cases, the combination of the positive family history for cardiovascular diseases and increased total cholesterol and LDL cholesterol levels should suggest the diagnosis of FH. Pharmaceutical agents inhibiting the cholesterol synthesis have been researched very little in children and are not registered in the Netherlands. Nevertheless, drug treatment of children with FH is advisable because of the better possibilities to make a definite diagnosis and the early occurrence of coronary heart disease. If this treatment were indicated before patients reach adult age, the question arises whether screening for FH of children in families in which this disorder prevails, should not be promoted more strongly.

[Higher prevalence of familial hypercholesterolemia than expected in adult patients of four family practices in Netherlands]. / Prevalentie van familiaire hypercholesterolemie onder volwassenen in vier huisartsenpraktijken hoger dan werd aangenomen.

OBJECTIVE: To determine the prevalence of familial hypercholesterolaemia (FH). DESIGN: Patient record screening, questionnaire and if necessary, case finding. METHODS: Over the period mid-1990-mid-1992 (approximately 2.5 years) 8,800 adult individuals (age 18 years and over) in 4 general practices in Hoofddorp, the Netherlands, were screened for risk factors for coronary artery disease and invited for further analysis. Of the 3,289 selected and invited individuals 2,719 (83%) were investigated. Total cholesterol concentrations were investigated 3 times and if the mean value was above 8.0 mmol/l patients were referred to a lipid clinic to investigate the possible existence of FH. RESULTS: 114 patients were eligible for referral to a lipid clinic of whom 92 (81%) were indeed referred. Of these, 38 patients were diagnosed with FH: 23 men and 15 women, with a mean age of 47.7 years (range: 21-74). CONCLUSION: The prevalence of FH in this investigated population was at least 1:232. This is more than 1:500, the estimated number of FH patients in the Dutch population.

[Tracing of patients with familial hypercholesterolemia in the Netherlands]. / Opsporing van patiënten met familiaire hypercholesterolemie in Nederland.

OBJECTIVE: To inventory the possibilities of tracing relatives of patients with familial hypercholesterolaemia (FH) by means of family tree research and DNA diagnostics. DESIGN: Descriptive. METHOD: Blood from patients with the clinical diagnosis of 'FH' was sent, through one of the lipid outpatient clinics in the country, to the Foundation for Tracing Hereditary Hypercholesterolaemia (StOEH) for DNA examination, to characterize the genetic defect. If a mutation was diagnosed in this index patient, he was invited by telephone by a StOEH staff member to have DNA testing done in relatives (especially those of the first degree). The data were stored in a data base. The analysis concerns the patients approached in 1994-1997, as well as those in whom the serum concentration of LDL cholesterol was also determined in 1993-1995. RESULTS: A total of 3013 persons were approached and examined: 146 index patients and 2867 relatives. The DNA diagnosis of 'FH' was made in 1067 relatives (37.2%), 585 (54.8%) women and 482 (45.2%) men. Of these, 21.2% were younger than 20 years, 37.0% 20-39 years, 26.6% 40-59 years and 15.2% > or = 60 years; 44.1% reported being known with a raised cholesterol level, 29.4% were treated with cholesterol-reducing drugs and 6.1% were suffering from a cardiovascular disease. Of the 990 persons in whom the serum LDL cholesterol level was determined, 325 (32.8%) were carriers of a mutation in the LDL receptor gene. 21.2% Of them had a LDL cholesterol level < P95. In the non-carrier group, 14.6% had a serum LDL cholesterol level > P95. CONCLUSION: Tracing FH patients is feasible in practice and leads to detection of as yet untreated patients.

APOE1 mutation in a patient with type III hyperlipoproteinaemia: detailed genetic analysis required.

We present the case of a patient with clinical features of familial dysbetalipoproteinaemia (FD) including high levels of total cholesterol, hypertriglyceridaemia and the presence of palmar xanthomas. Whereas genotype analysis identified the APOE3E3 isoform, sequence analysis revealed the presence of one APOE1 allele due to a mutation, p.Lys164Glu, which leads to loss of function of apolipoprotein E (ApoE), a rare cause of dominant FD.

Proteinuria in early childhood due to familial LCAT deficiency caused by loss of a disulfide bond in lecithin:cholesterol acyl transferase.

INTRODUCTION: Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare recessive disorder of cholesterol metabolism characterized by the absence of high density lipoprotein (HDL) and the triad of corneal opacification, hemolytic anemia and glomerulopathy. PATIENTS: We here report on FLD in three siblings of a kindred of Moroccan descent with HDL deficiency. In all cases (17, 12 and 3 years of age) corneal opacification and proteinuria were observed. In the 17-year-old female proband, anemia with target cells was observed. RESULTS: Homozygosity for a mutation in LCAT resulted in the exchange of cysteine to tyrosine at position 337, disrupting the second disulfide bond in LCAT. LCAT protein and activity were undetectable in the patients' plasma and in media of COS7 cells transfected with an expression vector with mutant LCAT cDNA. Upon treatment with an ACE inhibitor and a thiazide diuretic, proteinuria in the proband decreased from 6g to 2g/24h. CONCLUSION: This is the first report that FLD can cause nephropathy at a very early age.