Clinical and imaging features of women with polygenic partial lipodystrophy: a case series.

BACKGROUND: Familial partial lipodystrophy (FPLD) is an inherited disorder of white adipose tissue that causes premature cardiometabolic disease. There is no clear diagnostic criteria for FPLD, and this may explain the under-detection of this condition. AIM: This pilot study aimed to describe the clinical features of women with FPLD and to explore the value of adipose tissue measurements that could be useful in diagnosis. METHODS: In 8 women with FPLD and 4 controls, skinfold measurements, DXA and whole-body MRI were undertaken. RESULTS: Whole genome sequencing was negative for monogenic metabolic causes, but polygenic scores for partial lipodystrophy were elevated in keeping with FPLD type 1. The mean age of diagnosis of DM was 31 years in the FPLD group. Compared with controls, the FPLD group had increased HOMA-IR (10.3 vs 2.9, p = 0.028) and lower mean thigh skinfold thickness (19.5 mm vs 48.2 mm, p = 0.008). The FPLD group had lower percentage of leg fat and an increased ratio of trunk to leg fat percentage on DXA. By MRI, the FPLD group had decreased subcutaneous adipose tissue (SAT) volume in the femoral and calf regions (p < 0.01); abdominal SAT, visceral adipose tissue, and femoral and calf muscle volumes were not different from controls. CONCLUSION: Women with FPLD1 in Singapore have significant loss of adipose but not muscle tissue in lower limbs and have early onset of diabetes. Reduced thigh skinfold, and increased ratio of trunk to leg fat percentage on DXA are potentially clinically useful markers to identify FPLD1.

Cascade testing of children and adolescents for elevated Lp(a) in pedigrees with familial Hypercholesterolaemia.

Elevated plasma lipoprotein(a) [Lp(a)] is a common, inherited condition independently causing cardiovascular disease. Recent expert recommendations suggest opportunistically testing for elevated Lp(a) during cascade testing for familial hypercholesterolaemia (FH). We investigated the effectiveness of detecting elevated Lp(a) in 103 children and adolescents who were first-degree relatives of 66 adult index FH cases as part of an established FH cascade screening program. The yield of detection of elevated Lp(a) using a threshold of ≥30 mg/dL in children and adolescents was assessed. Cascade testing from FH index cases with elevated Lp(a) ≥50 mg/dL identified 1 case of Lp(a) ≥30 mg/dL for every 2 children or adolescents tested. In contrast, opportunistic screening from index cases with FH but normal Lp(a) levels demonstrated 1 case of Lp(a) ≥30 mg/dL for every 7.5 children or adolescents tested (p < 0.001). In conclusion, cascade testing for elevated Lp(a) from index cases with FH and elevated Lp(a) is effective in identifying new cases of elevated Lp(a).

MK-0616: an oral PCSK9 inhibitor for hypercholesterolemia treatment.

INTRODUCTION: Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of morbidity and mortality worldwide. Lowering LDL-cholesterol, by lifestyle modification or therapeutically, reduces the risk of ASCVD. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a protein which binds to the LDL-receptor and induces degradation, is a clinically validated target to lower LDL-cholesterol. Injectable PCSK9 inhibitor therapies have demonstrated substantial reductions in LDL-cholesterol with associated decreased risk of ASCVD events. AREAS COVERED: MK-0616 is an orally bioavailable, renally excreted, macrocyclic peptide inhibitor of PCSK9. The article provides an understanding of the chemistry and development, pharmacokinetic and pharmacodynamic characteristics of MK-0616 and insight into its clinical efficacy and safety. In clinical trials, MK-0616 produced dose-dependent reductions in LDL-cholesterol, non-HDL-cholesterol, and apolipoprotein (apo) B levels. Furthermore, MK-0616 modestly lowered lipoprotein (a) [Lp(a)]. EXPERT OPINION: MK-0616 is a potent, oral macrocyclic peptide inhibitor of PCSK9 that is not only able to reduce LDL-cholesterol, non-HDL-cholesterol, and apoB, but can also lower Lp(a). Safety and tolerability studies reported to date are promising. MK-0616 may offer advantages over injectable anti-PCSK9 therapies in terms of ease of dosing, patient preference and cost. The results from phase III trials of MK-0616 on cardiovascular outcomes are awaited with interest.

Shariant platform: Enabling evidence sharing across Australian clinical genetic-testing laboratories to support variant interpretation.

Sharing genomic variant interpretations across laboratories promotes consistency in variant assertions. A landscape analysis of Australian clinical genetic-testing laboratories in 2017 identified that, despite the national-accreditation-body recommendations encouraging laboratories to submit genotypic data to clinical databases, fewer than 300 variants had been shared to the ClinVar public database. Consultations with Australian laboratories identified resource constraints limiting routine application of manual processes, consent issues, and differences in interpretation systems as barriers to sharing. This information was used to define key needs and solutions required to enable national sharing of variant interpretations. The Shariant platform, using both the GRCh37 and GRCh38 genome builds, was developed to enable ongoing sharing of variant interpretations and associated evidence between Australian clinical genetic-testing laboratories. Where possible, two-way automated sharing was implemented so that disruption to laboratory workflows would be minimized. Terms of use were developed through consultation and currently restrict access to Australian clinical genetic-testing laboratories. Shariant was designed to store and compare structured evidence, to promote and record resolution of inter-laboratory classification discrepancies, and to streamline the submission of variant assertions to ClinVar. As of December 2021, more than 14,000 largely prospectively curated variant records from 11 participating laboratories have been shared. Discrepant classifications have been identified for 11% (28/260) of variants submitted by more than one laboratory. We have demonstrated that co-design with clinical laboratories is vital to developing and implementing a national variant-interpretation sharing effort. This approach has improved inter-laboratory concordance and enabled opportunities to standardize interpretation practices.

A variant in the fibronectin (FN1) gene, rs1250229-T, is associated with decreased risk of coronary artery disease in familial hypercholesterolaemia.

BACKGROUND: Increased risk of coronary artery disease (CAD) in familial hypercholesterolaemia (FH) is modified by factors beyond defects in the low-density lipoprotein receptor pathway. The rs1250229-T single nucleotide polymorphism (SNP) in the FN1 gene is associated with CAD in genome-wide association studies and is in linkage disequilibrium with another SNP (rs1250259-T) in FN1 that is associated with decrease fibronectin secretion. OBJECTIVE: We investigated whether rs1250229-T was also associated with prevalent CAD in patients with genetically confirmed FH. METHODS: We collected clinical data from 256 patients with genetically confirmed FH. The FN1 rs1250229 SNP was genotyped on a SEQUENOM platform. The association between rs1250229-T and prevalent CAD was assessed using simple and multiple regression analyses. RESULTS: In patients with FH, the FN1 rs1250229-T (minor) allele was a significant negative predictor of prevalent CAD (odds ratio [OR] 0.353; 95% confidence interval [CI] 0.193 - 0.647; P = 0.001). FN1 rs1250229-T remained a significant predictor of prevalent CAD after adjusting for age, sex, obesity, hypertension, smoking status and lipoprotein(a) concentration (OR 0.200; 95% CI 0.091 - 0.441; P < 0.001). CONCLUSION: The FN1 rs1250229-T allele is inversely associated with CAD in patients with genetically confirmed FH, independently of traditional risk factors. While this finding requires replication, it suggests that the biology of fibronectin may contribute to variation in the risk of CAD in FH.

Monogenic diabetes due to an INSR mutation in a child with severe insulin resistance.

SUMMARY: We report a case of an 11-year-old girl presenting with a new diagnosis of diabetes associated with a heterozygous missense mutation in the insulin receptor (INSR) gene. This case highlights that INSR gene variants can be a cause for monogenic diabetes in children and adolescents and the need for genetic evaluation in atypical presentations of diabetes. We also describe the possible role of metformin in treating individuals with type A insulin resistance syndrome due to INSR gene variants. LEARNING POINTS: Insulin receptor (INSR) gene variants can be a cause of monogenic diabetes in children and adolescents. Genetic evaluation should be considered in children and adolescents with type 2 diabetes (T2D), particularly where there is an atypical presentation and/or positive family history. Metformin may have a role in the treatment of type A insulin resistance syndrome due to heterozygous mutation of the INSR gene.

Incidental diagnosis of LPL deficiency in an infant presenting with an acute respiratory infection.

Lipoprotein lipase (LPL) deficiency is an extremely rare disorder of lipid metabolism known to cause hypertriglyceridaemia in childhood. We report the incidental diagnosis of LPL deficiency in an infant presenting with an acute respiratory tract infection. The patient was initially treated for a lower respiratory tract infection, but was subsequently found to have milky appearance of the serum, with a triglyceride concentration greater than 1000 mg/dL. Clinical examination revealed hepatosplenomegaly. Genetic analysis showed that the patient was a compound heterozygote for two rare likely pathogenic LPL variants c.808C>G p.(Arg270Gly) and c.1019-3C>G. She was commenced on a low-fat diet with the addition of medium chain triglyceride formula. At follow-up, her serum triglyceride level was normal.

The Clinical Genome Resource (ClinGen) Familial Hypercholesterolemia Variant Curation Expert Panel consensus guidelines for LDLR variant classification.

PURPOSE: In 2015, the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) published consensus standardized guidelines for sequence-level variant classification in Mendelian disorders. To increase accuracy and consistency, the Clinical Genome Resource Familial Hypercholesterolemia (FH) Variant Curation Expert Panel was tasked with optimizing the existing ACMG/AMP framework for disease-specific classification in FH. In this study, we provide consensus recommendations for the most common FH-associated gene, LDLR, where >2300 unique FH-associated variants have been identified. METHODS: The multidisciplinary FH Variant Curation Expert Panel met in person and through frequent emails and conference calls to develop LDLR-specific modifications of ACMG/AMP guidelines. Through iteration, pilot testing, debate, and commentary, consensus among experts was reached. RESULTS: The consensus LDLR variant modifications to existing ACMG/AMP guidelines include (1) alteration of population frequency thresholds, (2) delineation of loss-of-function variant types, (3) functional study criteria specifications, (4) cosegregation criteria specifications, and (5) specific use and thresholds for in silico prediction tools, among others. CONCLUSION: Establishment of these guidelines as the new standard in the clinical laboratory setting will result in a more evidence-based, harmonized method for LDLR variant classification worldwide, thereby improving the care of patients with FH.

Cascade testing for elevated lipoprotein(a) in relatives of probands with familial hypercholesterolaemia and elevated lipoprotein(a).

BACKGROUND AND AIMS: Familial hypercholesterolaemia (FH) and elevated plasma lipoprotein(a) [Lp(a)] are inherited conditions independently associated with atherosclerotic cardiovascular disease. This study investigated the detection of new cases of elevated Lp(a) during cascade testing of relatives of probands with a definite diagnosis of FH and elevated Lp(a) (≥50 mg/dL). METHODS: Relatives from 62 adult probands were tested for FH genetically and for elevated Lp(a) using an immunoassay. The prevalence and yield of new cases of FH with or without elevated Lp(a) among relatives and the association between the detection of elevated Lp(a) and the Lp(a) concentration of the probands were assessed. RESULTS: Among 162 relatives tested (136 adults and 26 children), the prevalence of FH and elevated Lp(a) was 60.5% and 41.4%, respectively: FH alone was detected in 31.5%, elevated Lp(a) alone in 12.3%, FH with elevated Lp(a) in 29.0%, and neither disorder in 27.2% of the relatives. Cascade testing detected a new case of FH, elevated Lp(a) and FH with elevated Lp(a) for every 1.5, 2.1 and 3.0 relatives tested, respectively. The proportion of relatives detected with elevated Lp(a) was significantly higher when tested from probands with Lp(a) ≥100 mg/dL compared with those from probands with Lp(a) between 50 and 99 mg/dL (53% vs 34%, p = 0.018). The concordance between the detection of FH and elevated Lp(a) was 56.2% (kappa statistic 0.154), indicating a poor agreement. CONCLUSIONS: A dual approach to cascade testing families for FH and high Lp(a) from appropriate probands can effectively identify not only new cases of FH, but also new cases of elevated Lp(a) with or without FH. The findings accord with the co-dominant and independent heritability of FH and Lp(a).

Pilot study of universal screening of children and child-parent cascade testing for familial hypercholesterolaemia in Australia.

AIM: Familial hypercholesterolaemia (FH) is a common and treatable cause of premature coronary artery disease. However, the majority of individuals with FH remain undiagnosed. This study investigated the feasibility, acceptability and cost-effectiveness of screening children aged 1-2 years for FH at the time of an immunisation. METHODS: Children 1-2 years of age were offered screening for FH with a point-of-care total cholesterol (TC) test by capillary-collected blood sample at the time of an immunisation. An additional blood sample was taken to allow genetic testing if the TC level was above the 95th percentile (>5.3 mmol/L). Parents of children diagnosed with FH were offered testing. Following detection of the affected parent, cascade testing of their first-degree blood relatives was performed. RESULTS: We screened 448 children with 32 (7.1%) having a TC ≥ 5.3 mmol/L. The FH diagnosis was confirmed in three children (1:150 screened). Reverse cascade testing of other family members identified a further five individuals with FH; hence, eight new cases of FH were diagnosed from screening 448 children (1:56 screened). Ninety-six percent of parents would screen future children for FH. The approach was cost-effective, at $3979 per quality-adjusted life year gained. CONCLUSION: In Western Australia, universal screening of children aged 1-2 years for FH, undertaken at the time of an immunisation, was a feasible and effective approach to detect children, parents and other blood relatives with FH. The approach was acceptable to parents and is potentially a highly cost-effective detection strategy for families at risk of FH.

Protective lipid-lowering variants in healthy older individuals without coronary heart disease.

OBJECTIVE: Genetic variants that disrupt the function of the PCSK9 (proprotein convertase subtilisin kexin type 9) and APOB (apolipoprotein B)genes result in lower serum low-density lipoprotein cholesterol (LDL-C) levels and subsequently confer protection against coronary heart disease (CHD). The objective of this study was to measure the prevalence and selective advantage of such variants among healthy older individuals without a history of CHD. METHODS: We performed targeted sequencing of the PCSK9 and APOB genes in 13 131 healthy individuals without CHD aged 70 years or older enrolled into the ASPirin in Reducing Events in the Elderly trial. We detected variants in the PCSK9 and APOB genes with predicted loss-of-function. We associated variant carrier status with serum LDL-C and total cholesterol (TC) levels at the time of study enrolment, adjusting for statin use. RESULTS: We detected 22 different rare PCSK9/APOB candidate variants with putative lipid-lowering effect, carried by 104 participants (carrier rate 1 in 126). Serum LDL-C and TC concentrations for rare PCSK9/APOB variant carriers were consistently lower than non-carriers. Rare variant carrier status was associated with 19.4 mg/dL (14.6%) lower LDL-C, compared with non-carriers (p≤0.001, adjusted for statin use). Statin prescriptions were less prevalent in rare variant carriers (16%) than non-carriers (35%). The more common PCSK9 R46L variant (rs11591147-T) was associated with 15.5 mg/dL (11.8%) lower LDL-C in heterozygotes, and 25.2 mg/dL (19.2%) lower LDL-C in homozygotes (both p≤0.001). CONCLUSIONS: Lipid-lowering genetic variants are carried by healthy older individuals and contribute to CHD-free survival. TRIAL REGISTRATION NUMBER: NCT01038583.

Lipoprotein apheresis and PCSK9 inhibitors for severe familial hypercholesterolaemia: Experience from Australia and New Zealand.

INTRODUCTION: Severe familial hypercholesterolaemia (FH) causes premature disability and death due to atherosclerotic cardiovascular disease and is refractory to standard lipid-lowering therapies. Lipoprotein apheresis (LA) has long been a standard of care for patients with severe FH, but is invasive, expensive and time-consuming for patients and their caregivers. Newer drug therapies, including the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, may reduce the need for LA. MATERIALS AND METHODS: We audited the records of 16 patients (eight homozygous, eight heterozygous) treated with LA in Australia and New Zealand, 14 of whom subsequently commenced PCSK9 inhibitor therapy. LA was performed by cascade filtration in all centres. RESULTS: LDL-cholesterol was acutely lowered by 69 ± 7% in patients with homozygous FH and by 72 ± 9% in those with heterozygous FH, representing time-averaged reductions of 36 ± 12% and 34 ± 5%, respectively. LA was well-tolerated, and patients reported comparable quality of life to population and disease-related norms. After commencement of PCSK9 inhibitors, four of seven patients with homozygous FH had meaningful biochemical responses, with a reduction in the frequency of LA permitted in one patient and complete cessation in another. Four of seven patients with heterozygous FH were able to be managed without LA after commencing PCSK9 inhibitors. CONCLUSION: While PCSK9 inhibitors have reduced the need for LA, some patients with severe FH continue to require LA, and will require it for the foreseeable future. However, emerging therapies, including angiopoetin-like 3 inhibitors, may further reduce the need for LA.

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.

Coronary artery disease and the risk-associated LPA variants, rs3798220 and rs10455872, in patients with suspected familial hypercholesterolaemia.

BACKGROUND: The rs3798220 and rs10455872 single nucleotide polymorphisms (SNPs) in LPA are associated with increased plasma concentrations of lipoprotein(a) [Lp(a)] and coronary artery disease (CAD). METHODS: We investigated the association between rs3798220 and rs10455872 and prevalent CAD in 763 patients with suspected familial hypercholesterolaemia (FH). The rs3798220 and rs10455872 SNPs in LPA were detected using a SEQUENOM platform. RESULTS: Both LPA SNPs were significantly associated with CAD, but only rs3798220 after adjustment for other risk factors (odds ratio [OR] 2.05; 95% confidence interval [CI] 1.02-4.12; p = 0.045), and neither after adjustment for Lp(a) concentrations. Both SNPs were positively and independently associated with increased Lp(a) (rs3798220: OR 1.27; 95% CI 0.96-1.57; p < 0.001. rs10455872: OR 1.41; 95% CI 1.24-1.58; p < 0.001). Plasma concentrations of Lp(a) were independently associated with prevalent CAD (OR 1.28; 95% CI 1.08-1.52, p = 0.005) after adjustment for LPA SNPs and other cardiovascular risk factors. While both the rs3798220 and rs10455872 SNPs were associated with Lp(a) concentrations and prevalent CAD in patients with suspected FH, this was not independent of Lp(a) concentration. CONCLUSIONS: Quantification of Lp(a) is more likely to be useful than assessment of these Lp(a)-associated SNPs to augment CAD risk prediction.

Design, development and deployment of a web-based patient registry for rare genetic lipid disorders.

Rare genetic lipid disorders comprise all the monogenic disorders of lipoprotein metabolism with the exception of heterozygous familial hypercholesterolaemia (FH). The creation and maintenance of patient registries is critical for disease monitoring, improving clinical best practice, facilitating research and enabling the development of novel therapeutics, but very few disease-specific rare genetic lipid disorder registries currently exist. Our aim was to design, develop and deploy a web-based patient registry for rare genetic lipid disorders. The Rare Genetic Lipid Disorders Registry is based on the FH Australasia Network (FHAN) Registry, which has been operating since 2015. The Rare Genetic Lipid Disorders Registry was deployed utilising the open-source Rare Disease Registry Framework (RDRF), which enables the efficient customisation and sustainable deployment of web-based registries. The Registry has been designed to capture longitudinal data on 13 rare genetic lipid disorders, with the ability to add more if required in the future. Recruitment of volunteers into the Registry is currently through the Royal Perth Hospital Lipid Disorders Clinic in Western Australia. Although in essence a clinic-based patient registry, the web-based design allows for expansion and distribution across Australia and beyond. Data collated by the Registry may ultimately improve the diagnosis, management and treatment of these conditions.