Phenotypical, Clinical, and Molecular Aspects of Adults and Children With Homozygous Familial Hypercholesterolemia in Iberoamerica.

OBJECTIVE: Characterize homozygous familial hypercholesterolemia (HoFH) individuals from Iberoamerica. Approach and Results: In a cross-sectional retrospective evaluation 134 individuals with a HoFH phenotype, 71 adults (age 39.3±15.8 years, 38.0% males), and 63 children (age 8.8±4.0 years, 50.8% males) were studied. Genetic characterization was available in 129 (96%). The majority (91%) were true homozygotes (true HoFH, n=79, 43.0% children, 46.8% males) or compound heterozygotes (compound heterozygous familial hypercholesterolemia, n=39, 51.3% children, 46.2% males) with putative pathogenic variants in the LDLR. True HoFH due to LDLR variants had higher total (P=0.015) and LDL (low-density lipoprotein)-cholesterol (P=0.008) compared with compound heterozygous familial hypercholesterolemia. Children with true HoFH (n=34) tended to be diagnosed earlier (P=0.051) and had a greater frequency of xanthomas (P=0.016) than those with compound heterozygous familial hypercholesterolemia (n=20). Previous major cardiovascular events were present in 25 (48%) of 52 children (missing information in 2 cases), and in 43 (67%) of 64 adults with LDLR variants. Children who are true HoFH had higher frequency of major cardiovascular events (P=0.02), coronary heart (P=0.013), and aortic/supra-aortic valve diseases (P=0.022) than compound heterozygous familial hypercholesterolemia. In adults, no differences were observed in major cardiovascular events according to type of LDLR variant. From 118 subjects with LDLR variants, 76 (64%) had 2 likely pathogenic or pathogenic variants. In 89 subjects with 2 LDLR variants, those with at least one null allele were younger (P=0.003) and had a greater frequency of major cardiovascular events (P=0.038) occurring at an earlier age (P=0.001). CONCLUSIONS: There was a high frequency of cardiovascular disease even in children. Phenotype and cardiovascular complications were heterogeneous and associated with the type of molecular defect.

Unusual genetic variants associated with hypercholesterolemia in Argentina.

BACKGROUND AND AIMS: Marked hypercholesterolemia, defined as low density lipoprotein cholesterol (LDL-C) levels ≥ 190 mg/dL, may be due to LDLR, APOB, and PCSK9 variants. In a recent analysis, only 1.7% of cases had such variants. Our goal was to identify other potential genetic causes of hypercholesterolemia. METHODS: In a total of 51,253 subjects with lipid testing, 3.8% had elevated total cholesterol >300 mg/dL and/or LDL-C≥190 mg/dL. Of these, 246 were further studied, and 69 without kidney, liver, or thyroid disease and who met Dutch Lipid Clinic Network criteria of ≥6 points had DNA sequencing done at the LDLR, APOB, PCSK9, APOE, LDLRAP1, STAP1, ABCG5, ABCG8, CYP27A1, LIPA, LIPC, LIPG, LPL, and SCARB1 gene loci and also had 10 SNP analysis for a weighted high LDL-C genetic risk score. RESULTS: In the 69 subjects with genetic analyses, the following variants were observed in 37 subjects (53.6%): LDLR (n = 20, 2 novel), ABCG5/8 (n = 7, 2 novel), APOB (n = 3, 1 novel), CYP27A1 (n = 3, 1 novel), LIPA (n = 2, 1 novel), APOE (n = 2), LIPC (n = 1, novel), LIPG (n = 1, novel), and SCARB1 (n = 1); 14 subjects (20.3%) had a high polygenic score, with 4 (5.8%) having no variants. CONCLUSIONS: Our data indicate that in addition to variants in LDLR, APOB, PCSK9, APOE, LDLRAP1, and STAP1, variants in ABCG5/8, CYP27A1, LIPA, LIPC, and LIPG may be associated with hypercholesterolemia and such information should be used to optimize therapy.

Preliminary spectrum of genetic variants in familial hypercholesterolemia in Argentina.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated low-density lipoprotein cholesterol and early cardiovascular disease. As cardiovascular disease is a leading cause of mortality in Argentina, early identification of patients with FH is of great public health importance. OBJECTIVE: The aim of our study was to identify families with FH and to approximate to the characterization of the genetic spectrum mutations of FH in Argentina. METHODS: Thirty-three not related index cases were selected with clinical diagnosis of FH. Genetic analysis was performed by sequencing, multiplex ligation-dependent probe amplification, and bioinformatics tools. RESULTS: Twenty genetic variants were identified among 24 cases (73%), 95% on the low-density lipoprotein receptor gene. The only variant on APOB was the R3527Q. Four were novel variants: c.-135C>A, c.170A>C p.(Asp57Ala), c.684G>C p.(Glu228Asp), and c.1895A>T p.(Asn632Ile); the bioinformatics' analysis revealed clear destabilizing effects for 2 of them. The exon 14 presented the highest number of variants (32%). Four variants were observed in more than 1 case and the c.2043C>A p.(Cys681*) was carried by 18% of index cases. Two true homozygotes, 3 compound heterozygotes, and 1 double heterozygote were identified. CONCLUSION: This study characterizes for the first time in Argentina genetic variants associated with FH and suggest that the allelic heterogeneity of the FH in the country could have 1 relative common low-density lipoprotein receptor mutation. This knowledge is important for the genotype-phenotype correlation and for optimizing both cholesterol-lowering therapies and mutational analysis protocols. In addition, these data contribute to the understanding of the molecular basis of FH in Argentina.

Clinical and molecular aspects of familial hypercholesterolemia in Ibero-American countries.

BACKGROUND: There is little information about familial hypercholesterolemia (FH) epidemiology and care in Ibero-American countries. The Ibero-American FH network aims at reducing the gap on diagnosis and treatment of this disease in the region. OBJECTIVE: To describe clinical, molecular, and organizational characteristics of FH diagnosis in Argentina, Brazil, Chile, Colombia, Mexico, Portugal, Spain, and Uruguay. METHODS: Descriptive analysis of country data related to FH cascade screening, molecular diagnosis, clinical practice guidelines, and patient organization presence in Ibero-America. RESULTS: From a conservative estimation of an FH prevalence of 1 of 500 individuals, there should be 1.2 million heterozygous FH individuals in Ibero-America and roughly 27,400 were diagnosed so far. Only Spain, Brazil, Portugal, and Uruguay have active cascade screening programs. The prevalence of cardiovascular disease ranged from 10% to 42% in member countries, and the highest molecular identification rates are seen in Spain, 8.3%, followed by Portugal, 3.8%, and Uruguay with 2.5%. In the 3 countries with more FH patients identified (Spain, Portugal, and Brazil) between 10 and 15 mutations are responsible for 30% to 47% of all FH cases. Spain and Portugal share 5 of the 10 most common mutations (4 in low density lipoprotein receptor [LDLR] and the APOB3527). Spain and Spanish-speaking Latin American countries share 6 of the most common LDLR mutations and the APOB3527. LDL apheresis is available only in Spain and Portugal and not all countries have specific FH diagnostic and treatment guidelines as well as patient organizations. CONCLUSIONS: Ibero-American countries share similar mutations and gaps in FH care.

APOE -491 T allele may reduce the risk of atherosclerotic lesions among middle-aged women.

Genetic variability of the APOE gene confers susceptibility to coronary artery disease (CAD). Beyond variability on the coding region, polymorphisms in the regulatory region of the APOE gene have been associated with variation on plasma cholesterol levels. It has also been demonstrated a complex and multifactorial association between, APOE gene polymorphisms, gender, plasma lipids levels and risk of CAD. In the present case-control study, we examined polymorphisms -427 T/C and -491 A/T in the promoter region of APOE in relation to lipid profile and the coronary atherosclerosis, in a sample of Argentinean adults with (cases) and without (controls) atherosclerotic injuries regarding gender and age. In females below 60 years APOE -491 T allele was less prevalent in cases than in controls (OR 0.12, 95% CI 0.04-0.76). Among females cases the T allele was more frequent with increasing age (OR 0.49, 95% CI 0.27-0.90). Female up to 45 years who were carriers of the T allele showed lower levels of total (P = 0.01) and LDL cholesterol (P = 0.02) compared with non-carriers. Levels of total and LDL cholesterol increased with the age only in female carriers (P < 0.01 and P < 0.01). No differences were observed for HDL and TG levels. Allele C of polymorphism APOE -427 was associated with higher levels of triglycerides (P < 0.01). We conclude that, in middle-aged women, APOE -491 T allele contributes keeping lower levels of LDL cholesterol in the population studied, and would have a putative protective effect for the development of CAD.

Association between the APOE*4 allele and atherosclerosis is age dependent among Argentine males.

Several studies have shown evidence of an association between the *4 allele of apolipoprotein E (APOE) and coronary heart disease (CHD) in different populations. We determined the APOE genotype and total cholesterol (TC), triglycerides (TG), and high-density lipoprotein cholesterol (HDLC) values in 189 patients with angiographically evaluated atherosclerosis. The APOE*4 allele was found to be statistically significantly more frequent (odds ratio, 1.93; 95% confidence interval, 1.12-3.32) among male patients than in a randomly chosen population-based sample. No significant difference was found when female patients were compared to the general population. The APOE*4 allele was found primarily among young (30-45-year-old) male patients (p < 0.04). Despite the ascending linear tendency of the mean TC values for genotypes APOE*2/*3, APOE*3/*3, and APOE*3/ *4 reported in our case population, no differences were observed among our patients. We conclude that the APOE*4 allele is associated with an increased risk for atherosclerotic vascular disease, that this association has an age-dependent effect, and that it acts as a genetic factor that increases susceptibility to developing the disease in young to middle-aged male adults in our population.

Ultimos avances en el síndrome de fragilidad del cromosoma X / Last advances in fragile X chromosome syndrome

The Fragile X syndrome is one of the most frequent forms of mental retardation. The responsible mutation is an unstable repetitive sequence. Since the mutations discovery, the knowledge about the gene, its protein, function, expression, laboratory detection, phenotype-genotype relationship and risk of expansion, has enormously increased. This work pretends to review the recent advances in this syndrome in all its aspects.(AU)

Ultimos avances en el síndrome de fragilidad del cromosoma X / Last advances in fragile X chromosome syndrome

The Fragile X syndrome is one of the most frequent forms of mental retardation. The responsible mutation is an unstable repetitive sequence. Since the mutation's discovery, the knowledge about the gene, its protein, function, expression, laboratory detection, phenotype-genotype relationship and risk of expansion, has enormously increased. This work pretends to review the recent advances in this syndrome in all its aspects.