Homozygous Familial Hypercholesterolemia

Advancements in the Treatment of Homozygous Familial Hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH) is a rare genetic disorder with extreme elevations of low-density lipoprotein cholesterol (LDL-C) leading to premature atherosclerotic cardiovascular disease (ASCVD) as early as in childhood. Management of HoFH centers around aggressive and adequate reduction of LDL-C levels to slow the trajectory of ASCVD development. Historically, lowering LDL-C levels in HoFH has been challenging because of both the markedly elevated LDL-C levels (often ＞400 mg/dL) and reduced response to treatment options, such as statins, for which the mechanism of action requires a functional LDL receptor. However, the treatment landscape for HoFH has rapidly progressed over the last decade. While statins and ezetimibe remain first-line treatment, patients often require addition of multiple therapies to achieve goal LDL-C levels. The PCSK9 inhibitors are an important recent addition to the available treatment options, along with lomitapide, bile acid sequestrants, and, possibly, bempedoic acid. Additionally, ANGPTL3 has emerged as an important therapeutic target, with evinacumab being the first available ANGPTL3 inhibitor on the market for the treatment of patients with HoFH. For patients who cannot achieve adequate LDL-C reduction, lipoprotein apheresis may be necessary, with the added benefit of reducing lipoprotein(a) levels that carries an added risk if also elevated in patients with HoFH. Finally, gene therapy and genome editing using CRISPR/Cas-9 are moving through clinical development and may dramatically alter the future landscape of treatment for HoFH.

Effects of Different Types of Pathogenic Variants on Phenotypes of Familial Hypercholesterolemia

Objective: It has been shown that pathogenic variants are associated with poor clinical outcomes in patients with familial hypercholesterolemia (FH). However, data on the effect of different types of pathogenic variants on FH phenotype is limited.

Methods: We retrospectively investigated the associations between genotypes and phenotypes, including low-density lipoprotein (LDL) cholesterol level and the occurrence of major adverse cardiac events (MACEs), defined as cardiovascular death, myocardial infarction, unstable angina, or coronary artery revascularization, in patients with FH (N = 1,050, male/female = 490/560). Based on genotype, the patients were divided into the following three groups: patients without pathogenic variants, patients with missense variants, and patients with protein-truncating variants (PTVs). Cox proportional hazard model was used to identify the factors associated with MACEs.

Results: The median follow-up duration was 12.6 years (interquartile range = 9.5–17.9 years). There were 665 patients with FH-mutation (277 patients with missense variants and 388 patients with PTVs) and 385 patients without FH-mutation. Over the follow-up duration, 175 MACEs were observed. We identified 89 different pathogenic variants in the 665 patients with FH. LDL cholesterol level was found to be significantly higher in patients with PTVs (256 mg/dl) than in patients with missense variants (236 mg/dl) and patients without pathogenic variants (216 mg/dl). It was also found that PTVs and missense variants are significantly associated with MACEs (hazard ratio [HR] = 1.58, 95% confidence interval [CI] = 1.08–2.08, p = 0.0033 and HR = 3.24, 95% CI = 2.12–4.40, p = 3.9 × 10⁻⁶, respectively), independent of classical risk factors.

Conclusion: Pathogenic variants, especially PTVs, are significantly associated with poor outcomes in patients with FH. Genetic testing is useful for the diagnosis and risk stratification of patients with FH.

Individualized Treatment for Patients With Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is one of the most common and, therefore, important inherited disorders in preventive cardiology. This disease is mainly caused by a single pathogenic mutation in the low-density lipoprotein receptor or its associated genes. Moreover, it is correlated with a high risk of cardiovascular disease. However, the phenotype severity even in this monogenic disease significantly varies. Thus, the current study aimed to describe FH and its importance and the factors (inherited and acquired) contributing to differences in phenotype severity. Different lipid-modification therapies according to these factors can lead to individualized treatments, which are also essential in the general populations.

The Assessment of Carotid Atherosclerotic Plaque among Young Patients with Familial Hypercholesterolemia

Objective Few data exist regarding when atherosclerotic changes occur among patients with familial hypercholesterolemia (FH). Carotid ultrasonography is a non-invasive method of evaluating this issue. The present study (1) compared the clinical utilities of carotid intima-media thickness (cIMT) and carotid plaque score (cPS) and (2) estimated the onset and progression of carotid atherosclerosis among patients with heterozygous FH (HeFH). Methods We retrospectively analyzed 511 patients under 30 years old who underwent carotid ultrasonography at our hospital from 2006 to 2019. We classified them into the HeFH group (n=78, 21.4±5.9 years old) and non-FH group (n=433, 23.4±6.0 years old) based on the clinical diagnosis and compared their cIMT and cPS values. In addition, we estimated the onset and progression of carotid atherosclerosis among young HeFH patients. Results There was no significant difference in the cIMT between the HeFH and non-FH groups (0.44 mm vs. 0.42 mm, p=0.25). In contrast, the cPS was significantly higher in the HeFH group than in the non-FH group (1.11 vs. 0.26, p=0.002). The regression equation for cPS of HeFH group was Y=-2.05+0.15X (r=0.37, p<0.001). Conclusion An assessment based on the cPS rather than the cIMT appears to be better to capture the progress of carotid atherosclerosis among young HeFH patients. Carotid atherosclerosis may start to develop at 14 years old in patients with HeFH.

A Comprehensive Review of PCSK9 Inhibitors

Cardiovascular disease (CVD) is the leading cause of death in the United States and worldwide. A major risk factor for this condition is increased serum low-density lipoprotein cholesterol (LDL-C) levels for which statins have been successful in reducing serum LDL-C to healthy concentrations. However, patients who are statin intolerant or those who do not achieve their treatment goals while on high-intensity statin therapy, such as those with familial hypercholesterolemia, remain at risk. With the discovery of PCSK9 inhibitors, the ability to provide more aggressive treatment for patients with homozygous and heterozygous familial hypercholesterolemia has increased. Ezetimibe reduces LDL-C by 15%-20% when combined with statin.^2,3 Protein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been found to achieve profound reductions in LDL-C (54%-74%) when added to statins. They have shown dramatic effects at lowering major adverse cardiovascular events (MACE) in high-risk patients⁴ with LDL-C levels ≥70 mg/dL and can be used in populations that are statin intolerant or not at goal levels with maximally tolerated statin therapy. PCSK9 inhibitors also produce minimal side effects. Myopathy, a common side effect for patients on statins, has been rare in patients on PCSK9 inhibitors. Randomized trials have shown that reduction in LDL-C has translated to clinical benefits even in patients who have not achieved their LDL-C target.

Whole Exome Sequencing Insufficient for a Definitive Diagnosis of a Patient with Compound Heterozygous Familial Hypercholesterolemia

Homozygous familial hypercholesterolemia (HoFH) is a rare genetic disorder, and a genetic analysis is important to make a definitive diagnosis. A comprehensive genetic analysis using next generation sequencing (NGS) and whole exome sequencing (WES) is feasible. However, the application of NGS in the assessment of genomic structural variations is generally limited, and a substantial number of control samples are needed for such assessments. Thus, NGS alone is unlikely to detect genomic structural variations in a "singleton." We present the case of a patient with compound HeFH (heterozygous FH), whose causative mutations in the LDLR gene could not be identified by WES, necessitating the application of the multiplex ligation-dependent probe amplification (MLPA) technique.

First case series of Polish patients with cerebrotendinous xanthomatosis and systematic review of cases from the 21st century

Cerebrotendinous xanthomatosis (CTX) is an inborn error of metabolism caused by recessive variants in the cytochrome P450 CYP27A1 gene. CTX is said to manifest with childhood-onset chronic diarrhea and the classic triad of juvenile-onset cataracts, Achilles tendons xanthomas, and progressive ataxia. It is currently one of the few inherited neurometabolic disorders amenable to a specific treatment. The diagnosis may be significantly delayed resulting in permanent neurological impairment. A retrospective review of the clinical characteristics and diagnostic findings in case series of six Polish patients with CTX. Additional retrospective review of symptoms and pathogenic variants of 568 CTX available cases and case series from the past 20 years. To the best of our knowledge, this is the widest review of CTX cases reported in years 2000-2021. We report the largest cohort of Polish patients ever published, with the identification of two hot-spot mutations. During the review of available 568 cases, we found significant differences in the clinical phenotypes and the localization of variants within the gene between Asian and non-Asian populations. These findings may facilitate molecular testing in the Polish and Asian populations. Invariably better screening for CTX and wider awareness is needed.

Prospective Registry Study of Primary Dyslipidemia (PROLIPID): Rationale and Study Design

Introduction: Primary dyslipidemias are inherited disorders in plasma lipoprotein metabolism that lead to serious cardiovascular and other complications. The Japanese Ministry of Health, Labor and Welfare (MHLW) covers medical expenses, under the Research Program on Rare and Intractable Diseases, for homozygous familial hypercholesterolemia (FH), familial chylomicronemia, sitosterolemia, cerebrotendinous xanthomatosis, lecithin:cholesterol acyltransferase deficiency, Tangier disease, and abetalipoproteinemia. Apolipoprotein A1 deficiency, heterozygous FH, and type III hyperlipoproteinemia are covered by the MHLW Pediatric Chronic Disease Program. Heterozygous FH and type III hyperlipoproteinemia are also important for their relatively common prevalence and, accordingly, high impact on Japanese public health by significant contribution to the overall prevalence of cardiovascular diseases. Therefore, a systemic survey of these diseases is mandatory to estimate their actual situation, such as prevalence, clinical manifestations, and prognoses among the Japanese population. The impact of these rare and intractable diseases on cardiovascular and other complications will likely be higher among Japanese people than other ethnicities because the general Japanese population has many cardioprotective aspects. The current study intends to conduct a multicenter registry of these diseases to assess their demographics and clinical features comprehensively.

Methods and Analysis: The Prospective Registry Study of Primary Dyslipidemia is a registry-based prospective, observational, multicenter cohort study in Japan, enrolling patients who fulfill the Japanese clinical criteria of the primary dyslipidemias listed above, from 26 participating institutes from August 2015 to March 2023. A total of 1,000 patients will be enrolled in the study and followed for 10 years. Clinical parameters are collected, including physical and laboratory findings, genetic analysis, drugs, lifestyle management, and clinical events, especially cardiovascular events. The primary endpoint of this study is the new onset of cardiovascular disease and acute pancreatitis, and the secondary endpoint is death from any causes.

Ethics and Dissemination: This study complies with the Declaration of Helsinki, the Ethical Guidelines for Medical and Health Research Involving Human Subjects, and all other applicable laws and guidelines in Japan. The institutional review boards have approved this study protocol at all participating institutes. The final results are to be published at appropriate international conferences and in peer-reviewed journals.