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Unraveling the genetic background of individuals with a clinical familial hypercholesterolemia phenotype

Publication . Medeiros, Ana Margarida; Alves, Ana Catarina; Miranda, Beatriz; Chora, Joana Rita; Bourbon, Mafalda; investigators of the Portuguese FH Study

Familial hypercholesterolemia (FH) is a common genetic disorder of lipid metabolism caused by pathogenic/likely pathogenic variants in LDLR, APOB, and PCSK9 genes. Variants in FH-phenocopy genes (LDLRAP1, APOE, LIPA, ABCG5, and ABCG8), polygenic hypercholesterolemia, and hyperlipoprotein (a) [Lp(a)] can also mimic a clinical FH phenotype. We aim to present a new diagnostic tool to unravel the genetic background of clinical FH phenotype. Biochemical and genetic study was performed in 1,005 individuals with clinical diagnosis of FH, referred to the Portuguese FH Study. A next-generation sequencing panel, covering eight genes and eight SNPs to determine LDL-C polygenic risk score and LPA genetic score, was validated, and used in this study. FH was genetically confirmed in 417 index cases: 408 heterozygotes and 9 homozygotes. Cascade screening increased the identification to 1,000 FH individuals, including 11 homozygotes. FH-negative individuals (phenotype positive and genotype negative) have Lp(a) >50 mg/dl (30%), high polygenic risk score (16%), other monogenic lipid metabolism disorders (1%), and heterozygous pathogenic variants in FH-phenocopy genes (2%). Heterozygous variants of uncertain significance were identified in primary genes (12%) and phenocopy genes (7%). Overall, 42% of our cohort was genetically confirmed with FH. In the remaining individuals, other causes for high LDL-C were identified in 68%. Hyper-Lp(a) or polygenic hypercholesterolemia may be the cause of the clinical FH phenotype in almost half of FH-negative individuals. A small part has pathogenic variants in ABCG5/ABCG8 in heterozygosity that can cause hypercholesterolemia and should be further investigated. This extended next-generation sequencing panel identifies individuals with FH and FH-phenocopies, allowing to personalize each person's treatment according to the affected pathway.

2023-12-18Journal article

Open access

Development and Validation of Screening Methods Applied to Familial Hypercholesterolemia Diagnosis

Publication . Albuquerque, João; Antunes, Marília; Antunes, Marília; Bourbon, Mafalda; Soares, Raquel

Familial hypercholesterolemia (FH) is an inherited disorder of lipid metabolism, characterized by increased low density lipoprotein cholesterol (LDLc) levels. If untreated, the severe dyslipidemia from birth leads to the early development of atherosclerosis, representing a major risk factor for cardiovascular disease (CVD). The early diagnosis of FH is associated with a signi cant reduction in CVD risk, supporting the introduction of risk mitigation strategies, such as cascade screening of rst degree relatives, and adequate lipid lowering therapy (LLT) as precociously as possible. The importance of genetic testing is emphasized by evidence that individuals with a con rmed pathogenic variant possess a signi cant increase in the risk of CVD when compared to subjects with FH-like phenotype for whom a causative variant is not detected. Nevertheless, molecular testing is still not available as a rst line diagnosis tool, and previous selection and strati cation of subjects to undergo this procedure should be made. Currently used clinical criteria, typically based on LDLc levels, family history of hypercholesterolemia and/ or premature CVD and presence of physical signs like tendon xanthomas, present the limitation of retaining a high number of false positive cases. This may constitute a heavy burden in terms of healthcare costs, and limits the access to the genetic study of a larger universe of true FH cases. The main purpose of this work was to develop alternative classi cation methods for FH diagnosis, based on di erent biochemical and clinical indicators, with improved ability to screen for FH cases in comparison to traditional clinical criteria. The metrics used for comparison range from the areas under the receiver operating characteristics (AUROC) and precision-recall (AUPRC) curves, to several operating characteristics (OC), to agreement tests, among others

2023-07-11Doctoral thesis

Restricted access