Autosomal recessive hypercholesterolemia: update for 2020

Analysis of low-density lipoprotein receptor gene mutations in a family with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is a common monogenic autosomal dominant disorder, primarily mainly caused by pathogenic mutations in the low-density lipoprotein receptor (LDLR) gene. Through phenotypic-genetic linkage analysis, two LDLR pathogenic mutations were identified in FH families: c.G1027A (p.Gly343Ser) and c.G1879A (p.Ala627Thr).

MATERIALS AND METHODS

Whole exome sequencing was conducted on the proband with familial hypercholesterolemia to identify the target gene and screen for potential pathogenic mutations. The suspicious responsible mutation sites in 14 family members were analyzed using Sanger sequencing to assess genotype-phenotype correlations. Mutant and wild type plasmids were constructed and transfected into HEK293T cells to evaluate LDLR mRNA and protein expression. In parallel, bioinformatics tools were employed to predict structural and functional changes in the mutant LDLR.

RESULTS

Immunofluorescence analysis revealed no significant difference in the intracellular localization of the p.Gly343Ser mutation, whereas protein expression of the p.Ala627Thr mutation was decreased and predominantly localized in the cytoplasm. Western blotting has showed that protein expression levels of the mutant variants were markedly declined in both cell lysates and supernatants. Enzyme linked immunosorbent assay has demonstrated that LDLR protein levels in the supernatant of cell culture medium was not significant different from those of the wild-type group. However, LDLR protein levels in the cell lysate of both the Gly343Ser and Ala627Thr variants groups were significantly lower than those in the wild-type group. Bioinformatic predictions further suggested that these mutations may affect post-translational modifications of the protein, providing additional insight into the mechanisms underlying the observed reduction in protein expression.

CONCLUSIONS

In this study, we identified two heterozygous pathogenic variants in the LDLR gene, c.G1027A (p.Gly343Ser) and c.G1879A (p.Ala627Thr), in a family with familial hypercholesterolemia. We also conducted preliminary investigations into the mechanisms by which these mutations contribute to disease pathology.

Hypercholesterolemia and inflammation-Cooperative cardiovascular risk factors

BACKGROUND

Maintaining low concentrations of plasma low-density lipoprotein cholesterol (LDLc) over time decreases the number of LDL particles trapped within the artery wall, slows the progression of atherosclerosis and delays the age at which mature atherosclerotic plaques develop. This substantially reduces the lifetime risk of atherosclerotic cardiovascular disease (ASCVD) events. In this context, plaque development and vulnerability result not only from lipid accumulation but also from inflammation.

RESULTS

Changes in the composition of immune cells, including macrophages, dendritic cells, T cells, B cells, mast cells and neutrophils, along with altered cytokine and chemokine release, disrupt the equilibrium between inflammation and anti-inflammatory mechanisms at plaque sites. Considering that it is not a competition between LDLc and inflammation, but instead that they are partners in crime, the present narrative review aims to give an overview of the main inflammatory molecular pathways linked to raised LDLc concentrations and to describe the impact of lipid-lowering approaches on the inflammatory and lipid burden. Although remarkable changes in LDLc are driven by the most recent lipid lowering combinations, the relative reduction in plasma C-reactive protein appears to be independent of the magnitude of LDLc lowering.

CONCLUSION

Identifying clinical biomarkers of inflammation (e.g. interleukin-6) and possible targets for therapy holds promise for monitoring and reducing the ASCVD burden in suitable patients.

The Importance of Genetic Testing for Familial Hypercholesterolemia: A Pediatric Pilot Study

Background and Objectives: Familial hypercholesterolemia (FH) is a genetic disease that is massively underdiagnosed worldwide. Affected patients are at high risk of cardiovascular events at young ages. Early intervention in childhood could help prevent heart attacks and cerebral strokes in these patients. Materials and Methods: We conducted an interventional study including 10 patients that previously underwent genetic testing for familial hypercholesterolemia. These patients received lifestyle and diet recommendations that they followed for a year before being reevaluated. Results: Patients with negative genetic testing were able to achieve lower levels in their lipid panel values compared to the patients with positive genetic testing, with lifestyle changes alone. LDL-cholesterol levels decreased by 18.5% in patients without FH while patients genetically confirmed with FH failed to achieve lower LDL-cholesterol levels without medication. Conclusions: Genetic testing for FH is not always part of screening algorithms for FH. Some studies even advise against it. Our study proved the importance of genetic testing for FH when suspecting this disorder and choosing the treatment course for patients.

Prevalence of genetically diagnosed familial hypercholesterolemia in Vietnamese patients with premature acute myocardial infarction

Familial hypercholesterolemia (FH) is a genetic disorder that results in elevated low-density lipoprotein cholesterol (LDL-C) levels, which manifest early in the first decades of life. It is a major cause of premature coronary artery disease worldwide, leading to significant public health challenges. The prevalence of genetically determined FH in patients with premature coronary artery disease remains underestimated, particularly in developing countries. This study aimed to assess the prevalence of genetically defined FH in Vietnamese patients with premature acute myocardial infarction (AMI) in the Vietnamese population. This cross-sectional study enrolled 218 consecutive patients diagnosed with premature AMI who underwent coronary angiography. The low-density lipoprotein receptor (LDLR), apolipoprotein B, and proprotein convertase subtilisin-kexin type 9 genes were analyzed by next-generation sequencing. FH was diagnosed according to Dutch Lipid Clinic Network criteria. Among the patients with premature AMI who underwent coronary angiography, the mean age was 46.9 ± 6.1 years, with a predominance of males (83.9%). The prevalence of potential FH diagnosed using Dutch Lipid Clinic Network criteria was 14.7% (definite FH, 6.0%; probable FH, 8.7%). Pathogenic or likely pathogenic variants in LDLR, apolipoprotein B, and proprotein convertase subtilisin-kexin type 9 were found in 9 of 218 patients (4.1%), all of which were causative mutations in LDLR. Patients with premature AMI and FH had significantly greater LDL-C levels (217.6 vs 125.7 mg/dL) and more severe coronary artery lesions, as assessed by the Gensini score (100.3 vs 60.5), than did those in the No FH group. The prevalence of genetically determined FH among Vietnamese patients with premature AMI is relatively high. Screening and diagnosis of hereditary conditions in patients with premature AMI are essential to improve early detection and management and reduce the burden of coronary artery disease in this population.

Consensus document on diagnosis and management of familial hypercholesterolemia from the Italian Society for the Study of Atherosclerosis (SISA)

AIMS

Familial Hypercholesterolemia (FH) is a genetic disorder of lipoprotein metabolism that causes an increased risk of premature atherosclerotic cardiovascular disease (ASCVD). Although early diagnosis and treatment of FH can significantly improve the cardiovascular prognosis, this disorder is underdiagnosed and undertreated. For these reasons the Italian Society for the Study of Atherosclerosis (SISA) assembled a Consensus Panel with the task to provide guidelines for FH diagnosis and treatment.

DATA SYNTHESIS

Our guidelines include: i) an overview of the genetic complexity of FH and the role of candidate genes involved in LDL metabolism; ii) the prevalence of FH in the population; iii) the clinical criteria adopted for the diagnosis of FH; iv) the screening for ASCVD and the role of cardiovascular imaging techniques; v) the role of molecular diagnosis in establishing the genetic bases of the disorder; vi) the current therapeutic options in both heterozygous and homozygous FH. Treatment strategies and targets are currently based on low-density lipoprotein cholesterol (LDL-C) levels, as the prognosis of FH largely depends on the magnitude of LDL-C reduction achieved by lipid-lowering therapies. Statins with or without ezetimibe are the mainstay of treatment. Addition of novel medications like PCSK9 inhibitors, ANGPTL3 inhibitors or lomitapide in homozygous FH results in a further reduction of LDL-C levels. LDL apheresis is indicated in FH patients with inadequate response to cholesterol-lowering therapies.

CONCLUSION

FH is a common, treatable genetic disorder and, although our understanding of this disease has improved, many challenges still remain with regard to its identification and management.

Leukocyte immunoglobulin-like receptor B1 (LILRB1) protects human multiple myeloma cells from ferroptosis by maintaining cholesterol homeostasis

Multiple myeloma (MM) is a hematologic malignancy characterized by uncontrolled proliferation of plasma cells in the bone marrow. MM patients with aggressive progression have poor survival, emphasizing the urgent need for identifying new therapeutic targets. Here, we show that the leukocyte immunoglobulin-like receptor B1 (LILRB1), a transmembrane receptor conducting negative immune response, is a top-ranked gene associated with poor prognosis in MM patients. LILRB1 deficiency inhibits MM progression in vivo by enhancing the ferroptosis of MM cells. Mechanistic studies reveal that LILRB1 forms a complex with the low-density lipoprotein receptor (LDLR) and LDLR adapter protein 1 (LDLRAP1) to facilitate LDL/cholesterol uptake. Loss of LILRB1 impairs cholesterol uptake but activates the de novo cholesterol synthesis pathway to maintain cellular cholesterol homeostasis, leading to the decrease of anti-ferroptotic metabolite squalene. Our study uncovers the function of LILRB1 in regulating cholesterol metabolism and protecting MM cells from ferroptosis, implicating LILRB1 as a promising therapeutic target for MM patients.

Contemporary lipid-lowering management and risk of cardiovascular events in homozygous familial hypercholesterolaemia: insights from the Italian LIPIGEN Registry

AIMS

The availability of novel lipid-lowering therapies (LLTs) has remarkably changed the clinical management of homozygous familial hypercholesterolaemia (HoFH). The impact of these advances was evaluated in a cohort of 139 HoFH patients followed in a real-world clinical setting.

METHODS AND RESULTS

The clinical characteristics of 139 HoFH patients, along with information about LLTs and low-density lipoprotein cholesterol (LDL-C) levels at baseline and after a median follow-up of 5 years, were retrospectively retrieved from the records of patients enrolled in the LIPid transport disorders Italian GEnetic Network-Familial Hypercholesterolaemia (LIPIGEN-FH) Registry. The annual rates of major atherosclerotic cardiovascular events (MACE-plus) during follow-up were compared before and after baseline. Additionally, the lifelong survival free from MACE-plus was compared with that of the historical LIPIGEN HoFH cohort. At baseline, LDL-C level was 332 ± 138 mg/dL. During follow-up, the potency of LLTs was enhanced and, at the last visit, 15.8% of patients were taking quadruple therapy. Consistently, LDL-C decreased to an average value of 124 mg/dL corresponding to a 58.3% reduction (Pt < 0.001), with the lowest value (∼90 mg/dL) reached in patients receiving proprotein convertase subtilisin/kexin type 9 inhibitors and lomitapide and/or evinacumab as add-on therapies. The average annual MACE-plus rate in the 5-year follow-up was significantly lower than that observed during the 5 years before baseline visit (21.7 vs. 56.5 per 1000 patients/year; P = 0.0016).

CONCLUSION

Our findings indicate that the combination of novel and conventional LLTs significantly improved LDL-C control with a signal of better cardiovascular prognosis in HoFH patients. Overall, these results advocate the use of intensive, multidrug LLTs to effectively manage HoFH.

Genetic Counseling and Genetic Testing for Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is one of the most common autosomal codominant Mendelian diseases. The major complications of FH include tendon and cutaneous xanthomas and coronary artery disease (CAD) associated with a substantial elevation of serum low-density lipoprotein levels (LDL). Genetic counseling and genetic testing for FH is useful for its diagnosis, risk stratification, and motivation for further LDL-lowering treatments. In this study, we summarize the epidemiology of FH based on numerous genetic studies, including its pathogenic variants, genotype-phenotype correlation, prognostic factors, screening, and usefulness of genetic counseling and genetic testing. Due to the variety of treatments available for this common Mendelian disease, genetic counseling and genetic testing for FH should be implemented in daily clinical practice.

[Primary disorders of lipid metabolism: their place in current dyslipidemia guidelines and treatment innovations]

According to current guidelines, the selection and intensity of lipid-effective therapies are based on the risk to be treated. The sole clinical categories of primary and secondary prevention of cardiovascular diseases result in over- and under-treatment, which may be a contributory cause of incomplete implementation of current guidelines in everyday practice. For the extent of benefit in cardiovascular outcome studies with lipid-lowering drugs, the importance of dyslipdemia for the pathogenesis of atherosclerosis-related diseases is crucial. Primary lipid metabolism disorders are characterized by life-long increased exposure to atherogenic lipoproteins. This article describes the relevance of new data for low density lipoprotein-effective therapy: inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9), adenosine triphosphate (ATP) citrate lyase with bempedoic acid, and ANGPTL3 with special consideration of primary lipid metabolism disorders, which are insufficiently taken into account, or not taken into account at all, in current guidelines. This is due to their apparently low prevalence rate and thus the lack of large outcome studies. The authors also discuss the consequences of increased lipoprotein (a), which cannot be sufficiently reduced until the ongoing intervention studies examining antisense oligonucleotides and small interfering RNA (siRNA) against apolipoprotein (a) are completed. Another challenge in practice is the treatment of rare, massive hypertriglyceridemia, especially with the aim of preventing pancreatitis. For this purpose, the apolipoprotein C3 (ApoC3) antisense oligonucleotide volenasorsen is available, which binds to the mRNA for ApoC3 and lowers triglycerides by around three quarters.

2023 Update on European Atherosclerosis Society Consensus Statement on Homozygous Familial Hypercholesterolaemia: new treatments and clinical guidance

This 2023 statement updates clinical guidance for homozygous familial hypercholesterolaemia (HoFH), explains the genetic complexity, and provides pragmatic recommendations to address inequities in HoFH care worldwide. Key strengths include updated criteria for the clinical diagnosis of HoFH and the recommendation to prioritize phenotypic features over genotype. Thus, a low-density lipoprotein cholesterol (LDL-C) >10 mmol/L (>400 mg/dL) is suggestive of HoFH and warrants further evaluation. The statement also provides state-of-the art discussion and guidance to clinicians for interpreting the results of genetic testing and for family planning and pregnancy. Therapeutic decisions are based on the LDL-C level. Combination LDL-C-lowering therapy-both pharmacologic intervention and lipoprotein apheresis (LA)-is foundational. Addition of novel, efficacious therapies (i.e. inhibitors of proprotein convertase subtilisin/kexin type 9, followed by evinacumab and/or lomitapide) offers potential to attain LDL-C goal or reduce the need for LA. To improve HoFH care around the world, the statement recommends the creation of national screening programmes, education to improve awareness, and management guidelines that account for the local realities of care, including access to specialist centres, treatments, and cost. This updated statement provides guidance that is crucial to early diagnosis, better care, and improved cardiovascular health for patients with HoFH worldwide.

Different clinical phenotypes of a pair of siblings with familial hypercholesterolemia: a case report and literature review

BACKGROUND

Familial hypercholesterolemia (FH) leads to high plasma low-density lipoprotein cholesterol (LDL-C) levels and early cardiovascular morbidity and mortality. We treated a pair of siblings with FH. The cardiovascular manifestations in the proband were more severe than those in his elder sister, although they had almost similar LDL-C levels, ages, and lifestyles. Herein, we report the cases of this family to explore the possible causes of clinical phenotypic differences within the same genetic background.

CASE PRESENTATION

We treated a 27-year-old male patient and his 30-year-old sister, both with FH. The coronary angiogram in the male patient revealed 80, 70, and 100% stenosis of the initial, distal right coronary artery branch, and left anterior descending branch, respectively, whereas his sister had almost no coronary stenosis. We treated them accordingly and performed family screening. We found that the LDL-C/particle discordance of the proband is much greater than that of his elder sister. In addition, the average size of LDL-C particle in the proband was smaller than that in his sister.

CONCLUSIONS

Patients with FH have a much higher risk of premature atherosclerotic cardiovascular disease, but the clinical manifestations are heterogeneous. The smaller LDL particle size may be the underlying cause for different clinical outcomes in this pair of FH cases and be a potential novel indicator for predicting the prognosis of FH.

Genetic Heterogeneity of Familial Hypercholesterolemia: Repercussions for Molecular Diagnosis

Genetics of Familial Hypercholesterolemia (FH) is ascribable to pathogenic variants in genes encoding proteins leading to an impaired LDL uptake by the LDL receptor (LDLR). Two forms of the disease are possible, heterozygous (HeFH) and homozygous (HoFH), caused by one or two pathogenic variants, respectively, in the three main genes that are responsible for the autosomal dominant disease: LDLR, APOB and PCSK9 genes. The HeFH is the most common genetic disease in humans, being the prevalence about 1:300. Variants in the LDLRAP1 gene causes FH with a recessive inheritance and a specific APOE variant was described as causative of FH, contributing to increase FH genetic heterogeneity. In addition, variants in genes causing other dyslipidemias showing phenotypes overlapping with FH may mimic FH in patients without causative variants (FH-phenocopies; ABCG5, ABCG8, CYP27A1 and LIPA genes) or act as phenotype modifiers in patients with a pathogenic variant in a causative gene. The presence of several common variants was also considered a genetic basis of FH and several polygenic risk scores (PRS) have been described. The presence of a variant in modifier genes or high PRS in HeFH further exacerbates the phenotype, partially justifying its variability among patients. This review aims to report the updates on the genetic and molecular bases of FH with their implication for molecular diagnosis.

Assessing the genetic burden of familial hypercholesterolemia in a large middle eastern biobank

BACKGROUND

The genetic architecture underlying Familial Hypercholesterolemia (FH) in Middle Eastern Arabs is yet to be fully described, and approaches to assess this from population-wide biobanks are important for public health planning and personalized medicine.

METHODS

We evaluate the pilot phase cohort (n = 6,140 adults) of the Qatar Biobank (QBB) for FH using the Dutch Lipid Clinic Network (DLCN) criteria, followed by an in-depth characterization of all genetic alleles in known dominant (LDLR, APOB, and PCSK9) and recessive (LDLRAP1, ABCG5, ABCG8, and LIPA) FH-causing genes derived from whole-genome sequencing (WGS). We also investigate the utility of a globally established 12-SNP polygenic risk score to predict FH individuals in this cohort with Arab ancestry.

RESULTS

Using DLCN criteria, we identify eight (0.1%) 'definite', 41 (0.7%) 'probable' and 334 (5.4%) 'possible' FH individuals, estimating a prevalence of 'definite or probable' FH in the Qatari cohort of ~ 1:125. We identify ten previously known pathogenic single-nucleotide variants (SNVs) and 14 putatively novel SNVs, as well as one novel copy number variant in PCSK9. Further, despite the modest sample size, we identify one homozygote for a known pathogenic variant (ABCG8, p. Gly574Arg, global MAF = 4.49E-05) associated with Sitosterolemia 2. Finally, calculation of polygenic risk scores found that individuals with 'definite or probable' FH have a significantly higher LDL-C SNP score than 'unlikely' individuals (p = 0.0003), demonstrating its utility in Arab populations.

CONCLUSION

We design and implement a standardized approach to phenotyping a population biobank for FH risk followed by systematically identifying known variants and assessing putative novel variants contributing to FH burden in Qatar. Our results motivate similar studies in population-level biobanks - especially those with globally under-represented ancestries - and highlight the importance of genetic screening programs for early detection and management of individuals with high FH risk in health systems.

Efficacy of Long-Term Treatment of Autosomal Recessive Hypercholesterolemia With Lomitapide: A Subanalysis of the Pan-European Lomitapide Study

Backgroundand aim: Autosomal recessive hypercholesterolemia (ARH) is a rare autosomal recessive disorder of low-density lipoprotein (LDL) metabolism caused by pathogenic variants in the LDLRAP1 gene. Like homozygous familial hypercholesterolemia, ARH is resistant to conventional LDL-lowering medications and causes a high risk of atherosclerotic cardiovascular diseases (ASCVDs) and aortic valve stenosis. Lomitapide is emerging as an efficacious therapy in classical HoFH, but few data are available for ARH.

Results: This is a subanalysis carried out on nine ARH patients included in the Pan-European Lomitapide Study. The age at starting lomitapide was 46 (interquartile range (IQR), 39.0–65.5) years, with a median treatment duration of 31.0 (IQR 14.0–40.5) months. At baseline, four (44.4%) patients had hypertension, one (11.1%) had diabetes mellitus, two (22.2%) were active smokers, and five (55.5%) reported ASCVD. The baseline LDL-C was 257.0 (IQR, 165.3–309.2) mg/dL. All patients were on statins plus ezetimibe, three were receiving Lipoprotein apheresis (LA), and one was also receiving proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i). The addition of lomitapide (mean dose, 10 mg) resulted in the achievement of a median on-treatment LDL-C of 101.7 mg/dL (IQR, 71.3–138.3; 60.4% reduction from baseline), with a best LDL-C value of 68.0 mg/dL (IQR, 43.7–86.7; 73.5% reduction from baseline). During follow-up, one patient stopped both PCSK9i and LA. Recurrence of ASCVD events was reported in one patient. The median on-treatment aspartate transaminase and alanine transaminase values were 31.1 (IQR, 22.6–48.3) U/L and 31.1 (IQR, 27.2–53.8) U/L, respectively. Among six ARH patients with available fibroscan examination, liver stiffness values recorded at the last visit were within the normal range (median, 4.7 KPa; IQR, 3.6–5.3 KPa).

Conclusion: Lomitapide is effective and safe in ARH therapy as well as in classical HoFH.

Etiologic Puzzle of Coronary Artery Disease: How Important Is Genetic Component?

In the modern era, coronary artery disease (CAD) has become the most common form of heart disease and, due to the severity of its clinical manifestations and its acute complications, is a major cause of morbidity and mortality worldwide. The phenotypic variability of CAD is correlated with the complex etiology, multifactorial (caused by the interaction of genetic and environmental factors) but also monogenic. The purpose of this review is to present the genetic factors involved in the etiology of CAD and their relationship to the pathogenic mechanisms of the disease. Method: we analyzed data from the literature, starting with candidate gene-based association studies, then continuing with extensive association studies such as Genome-Wide Association Studies (GWAS) and Whole Exome Sequencing (WES). The results of these studies revealed that the number of genetic factors involved in CAD etiology is impressive. The identification of new genetic factors through GWASs offers new perspectives on understanding the complex pathophysiological mechanisms that determine CAD. In conclusion, deciphering the genetic architecture of CAD by extended genomic analysis (GWAS/WES) will establish new therapeutic targets and lead to the development of new treatments. The identification of individuals at high risk for CAD using polygenic risk scores (PRS) will allow early prophylactic measures and personalized therapy to improve their prognosis.

The role of lipid metabolism in shaping the expansion and the function of regulatory T cells

Metabolic inflammation, defined as a chronic low-grade inflammation, is implicated in numerous metabolic diseases. In recent years, the role of regulatory T cells (Tregs) as key controllers of metabolic inflammation has emerged, but our comprehension on how different metabolic pathways influence Treg functions needs a deeper understanding. Here we focus on how circulating and intracellular lipid metabolism, in particular cholesterol metabolism, regulates Treg homeostasis, expansion, and functions. Cholesterol is carried through the bloodstream by circulating lipoproteins (chylomicrons, very low-density lipoproteins, low-density lipoproteins). Tregs are equipped with a wide array of metabolic sensors able to perceive and respond to changes in the lipid environment through the activation of different intracellular pathways thus conferring to these cells a crucial metabolic and functional plasticity. Nevertheless, altered cholesterol transport, as observed in genetic dyslipidemias and atherosclerosis, impairs Treg proliferation and function through defective cellular metabolism. The intracellular pathway devoted to the cholesterol synthesis is the mevalonate pathway and several studies have shown that this pathway is essential for Treg stability and suppressive activity. High cholesterol concentrations in the extracellular environment may induce massive accumulation of cholesterol inside the cell thus impairing nutrients sensors and inhibiting the mevalonate pathway. This review summarizes the current knowledge regarding the role of circulating and cellular cholesterol metabolism in the regulation of Treg metabolism and functions. In particular, we will discuss how different pathological conditions affecting cholesterol transport may affect cellular metabolism in Tregs.

Refinement of pathogenicity classification of variants associated with familial hypercholesterolemia: Implications for clinical diagnosis

BACKGROUND

The lack of functional evidence for most variants detected during the molecular screening of patients with clinical familial hypercholesterolemia (FH) makes the definitive diagnosis difficult.

METHODS

A total of 552 variants in LDLR, APOB, PCSK9 and LDLRAP1 genes found in 449 mutation-positive FH (FH/M+) patients were considered. Pathogenicity update was performed following the American College of Medical Genetics and Genomics (ACMG) guidelines with additional specifications on copy number variants, functional studies, in silico prediction and co-segregation criteria for LDLR, APOB and PCSK9 genes. Pathogenicity of LDLRAP1 variants was updated by using ACMG criteria with no change to original scoring.

RESULTS

After reclassification, the proportion of FH/M+ carriers of pathogenic (P) or likely pathogenic (LP) variants, and FH/M+ carriers of likely benign (LB) or benign (B) variants, was higher than that defined by standard criteria (81.5% vs. 79.7% and 7.1% vs. 2.7%). The refinement of pathogenicity classification also reduced the percentage of FH with variants of uncertain significance (VUS) (17.7% vs. 11.4%). After adjustment, the FH diagnosis by refined criteria best predicted LDL-C levels (P_adj <0.001). Notably, FH with VUS variants had higher LDL-C than those with LB (all P_adj ≤ 0.033), but similar to those with LP variants.

CONCLUSION

Accurate variant interpretation best predicts the increase of LDL-C levels and shows its clinical utility in the molecular diagnosis of FH.

Homozygous autosomal recessive hypercholesterolaemia in a South Asian child presenting with multiple cutaneous xanthomata

Autosomal recessive hypercholesterolemia (ARH; OMIM #603813) is an extremely rare disorder of lipid metabolism caused by loss-of-function variants in the LDL receptor adapter protein 1 (LDLRAP1) gene, which is characterized by severe hypercholesterolaemia and an increased risk of premature atherosclerotic cardiovascular disease. We report the case of an 11-year-old girl who presented with multiple painless yellowish papules around her elbows and knees of two-year duration. She had been reviewed by several general practitioners, with some of the papules having been excised, but without a specific diagnosis being made. The child was referred to a paediatric service for further evaluation and treatment of the cutaneous lesions, which appeared xanthomatous in nature. A lipid profile showed severe hypercholesterolaemia. Next generation sequencing analysis of a monogenic hypercholesterolaemia gene panel revealed homozygosity for a pathogenic frameshift mutation, c.71dupG, p.Gly25Argfs*9 in LDLRAP1. Her parents and brother, who were asymptomatic, were screened and found to be heterozygous carriers of the LDLRAP1 variant. There was no known consanguinity in the family. She was commenced on the HMG-CoA reductase inhibitor, atorvastatin, to good effect, with a ∼76% reduction in LDL-cholesterol at a dose of 50 mg per day. At six-month follow-up, there had been no obvious regression of the xanthomata, but importantly, no enlargement of, or the development of new papular lesions, have occurred. In summary, we report a child who presented with multiple cutaneous xanthomata and was confirmed to have ARH by the presence of a homozygous novel pathogenic frameshift variant in LDLRAP1.

Autosomal recessive hypercholesterolemia in a kindred of Syrian ancestry

Autosomal recessive hypercholesterolemia is a rare genetic disorder due to homozygosity or compound heterozygosity for mutations in the low-density lipoprotein receptor adapter protein 1 gene (LDLRAP1), resulting in elevated low-density lipoprotein cholesterol (LDL-C) levels, large xanthomas, and increased cardiovascular risk. Here, we describe a Danish family of Syrian ancestry carrying a frameshift mutation in LDLRAP1, previously only described in Sardinia and Sicily in Italy and in Spain. In 2 children homozygous for this mutation, we evaluate the effect of long-term lipid-lowering treatment with atorvastatin as monotherapy or in combination with ezetimibe. At referral to the lipid clinic at Viborg Regional Hospital, 3 of 4 children had LDL-C levels of 468, 538, and 371 mg/dL, respectively, with 1 child already showing cutaneous xanthomas at 10 years of age. For comparison, the fourth child and the parents had LDL-C levels of 85, 116, and 124 mg/dL. Genetic testing revealed that all 3 children with severely elevated LDL-C were homozygous for a rare frameshift mutation in LDLRAP1, p.His144GlnfsTer27 (c.431dupA), whereas the fourth child and both parents were heterozygous for this mutation. Lipid-lowering treatment was started in the 2 oldest children (at 10 and 7 years of age). Atorvastatin (40 mg/d) combined with ezetimibe (10 mg/d) reduced LDL-C by 75% in the first child and resulted in near-complete regression of xanthomas. In the second child, atorvastatin (40 mg/d) as monotherapy reduced LDL-C by 61%. Both regimens were superior to treatment with pravastatin as monotherapy (20 mg/d) and to pravastatin in combination with cholestyramine (2 g twice daily). High-intensity statin therapy alone or in combination with ezetimibe resulted in marked reductions in LDL-C in 2 children homozygous for a rare frameshift mutation in LDLRAP1 and lead to regression of large xanthomas.