Clinical Profile of Cardiac Involvement in Danon Disease: A Multicenter European Registry

An International Longitudinal Natural History Study of Patients With Danon Disease: Unique Cardiac Trajectories Identified Based on Sex and Heart Failure Outcomes

BACKGROUND

Danon disease is a rare X-linked dominant cardioskeletal myopathy caused by mutations in the lysosome-associated membrane protein-2 gene. Though the severe morbidity of disease in men is well established, longitudinal studies describing the trajectory of cardiovascular disease in both sexes are lacking.

METHODS AND RESULTS

Data were from the International Danon Disease Registry and includes retrospective data on 116 patients who provided informed consent between 2005 and 2022. The analysis included 116 patients with Danon disease with a median age of diagnosis of 15.2 years (10.0-25.2 years). Trends in echocardiographic parameters over time indicate decreased left ventricular ejection fraction and increased left ventricular end diastolic dimension regardless of sex and heart failure (HF) outcome; however, rate of change was increased in patients who experienced a HF outcome in both sexes. Left ventricular wall hypertrophy continues in men who have not yet experienced a HF outcome and stabilizes before HF outcome, while females have progressive left ventricular thinning regardless of HF outcome. Stratified analysis demonstrated 2 distinct groups of females: one who experienced HF outcome before 26 years of age and another group with this HF outcome after.

CONCLUSIONS

In this largest longitudinal natural history study of Danon disease to date, we confirmed that males present on average a decade earlier and demonstrate more progressive cardiac hypertrophy and HF than females. Notably, there may be a subset of females who are phenotypically similar to males with profound left ventricular hypertrophy that appears to stabilize or regress before HF outcome. Correlations between structural cardiac dysfunction and disease progression may permit risk stratification, refinement of treatment algorithms, and inform therapeutic trial design.

REGISTRATION

URL: https://clinicaltrials.gov/; Unique Identifier: NCT03766386.

Clinical and Genetic Profile of Chinese Children With Danon Disease: A Single-Center Retrospective Cohort Study

BACKGROUND

Danon disease (DD) is a rare X-linked dominant lysosomal storage disorder. Studies on DD pediatric patients are limited owing to the small number of cases and challenges in early detection.

METHODS

We retrospectively analysed clinical and genetic data of 29 pediatric patients who visited our hospital for treatment or genetic counselling for DD from July 2014 to December 2023.

RESULTS

The mean age at diagnosis was 7.2 ± 5.9 years for boys (n = 21) and 9.4 ± 5.0 years for girls (n = 8). Asymptomatic elevated liver transaminase or creatine kinase (CK) levels were initial manifestations detected in 10 male patients (48%) and absent in female patients. Hypertrophic cardiomyopathy (HCM) was observed in 20 male patients (95%) and 7 female patients (88%), whereas dilated cardiomyopathy (DCM) was not detected. Ventricular preexcitation (VP) was observed initially in 10 patients (36%) and in 15 (54%) at latest evaluation. Patients with VP had higher left ventricular posterior wall thickness in end-diastole z-scores than those without VP (5.6 ± 2.2 vs 3.5 ± 2.1; P = 0.029). During a median 2.7 years of follow-up, 2 male patients received heart transplants. One boy and 1 girl died of heart failure and sudden cardiac arrest, respectively. Twenty-three pathogenic LAMP2 variants were identified, including 7 novel variants.

CONCLUSIONS

A retrospective review of 29 DD cases suggests an underrecognised asymptomatic period in male DD patients, characterised by elevations in serum CK and transaminases. HCM appears to be the only cardiac manifestation in pediatric female patients, unlike a high incidence of DCM in adult female patients. The incidence of VP may increase with disease progression.

Phase 1 Study of AAV9.LAMP2B Gene Therapy in Danon Disease

BACKGROUND

Danon disease is a rare, X-linked, monogenic cardiomyopathy caused by mutations in the lysosomal-associated membrane 2 gene (LAMP2), which encodes the LAMP2 protein. In male patients, the predominant phenotype is progressive cardiac hypertrophy, cardiac dysfunction, and early death. There are no directed therapies for the disease.

METHODS

In this phase 1 study, we evaluated the safety and efficacy of a single infusion of RP-A501, a recombinant adeno-associated virus serotype 9 containing the transgene LAMP2B, which encodes an isoform of LAMP2. The primary outcomes were the safety and toxic effects of RP-A501, myocardial LAMP2 transduction and protein expression, stabilization of or reduction in heart-failure symptoms, and stabilization of or improvement in cardiac structure and function. Key secondary outcomes were sustained reduction in or stabilization of symptoms, immunologic response to RP-A501, end-stage heart failure, and overall survival. Exploratory outcomes included improvement in serologic markers of cardiac disease, patient-reported outcomes, and quality-of-life assessments.

RESULTS

RP-A501 infusion was administered to seven male patients with Danon disease: five who were 15 years of age or older and two who were between 11 and 14 years of age. All the patients received a transient immunomodulatory regimen of prednisone, tacrolimus or sirolimus, and rituximab. Phase 1 data over 24 to 54 months, including interim data from a long-term follow-up study, are reported here. One patient had complement-mediated thrombotic microangiopathy (grade 4) with thrombocytopenia and acute kidney injury. Three patients had glucocorticoid-related exacerbation (grade 3) of Danon disease-related skeletal myopathy. One patient with left ventricular systolic dysfunction at baseline had progressive heart failure and underwent transplantation 5 months after infusion. In the six patients with normal left ventricular ejection fraction at baseline, we observed cardiac LAMP2 protein expression and a reduction from baseline in or stabilization of the left ventricular mass index, preservation of left ventricular ejection fraction, and reduction in or stabilization of the levels of cardiac troponin I and N-terminal pro-B-type natriuretic peptide. At 24 to 54 months, all the patients were alive, with complete resolution of side effects.

CONCLUSIONS

A single infusion of RP-A501 appeared to be safe and was associated with cardiac LAMP2 expression and evidence of clinical improvement over a period of 24 to 54 months. (Funded by Rocket Pharmaceuticals; ClinicalTrials.gov number, NCT03882437.).

Advancing the access to cardiovascular diagnosis and treatment among women with cardiovascular disease: a joint British Cardiovascular Societies' consensus document

Despite significant progress in cardiovascular pharmacotherapy and interventional strategies, cardiovascular disease (CVD), in particular ischaemic heart disease, remains the leading cause of morbidity and mortality among women in the UK and worldwide. Women are underdiagnosed, undertreated and under-represented in clinical trials directed at management strategies for CVD, making their results less applicable to this subset. Women have additional sex-specific risk factors that put them at higher risk of future cardiovascular events. Psychosocial risk factors, socioeconomic deprivation and environmental factors have an augmented impact on women's cardiovascular health, highlighting the need for a holistic approach to care that considers risk factors specifically related to female biology alongside the traditional risk factors. Importantly, in the UK, even in the context of a National Health Service, there exist significant regional variations in age-standardised mortality rates among patients with CVD. Given most CVDs are preventable, concerted efforts are necessary to address the unmet needs and ensure parity of care for women with CVD. The present consensus document, put together by the British Cardiovascular Society (BCS)'s affiliated societies, specifically portrays the current status on the sex-related differences in the diagnosis and treatment of each of the major CVD areas and proposes strategies to overcome the barriers in accessing diagnoses and treatments among women. This document aims at raising awareness of the scale of the current problem and hopes to stimulate a multifaceted approach to address sex disparities and enable future comprehensive sex- and gender-based research through collaboration across different affiliated societies within the BCS.

Management of hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy is an important cause of heart failure and arrhythmias, including sudden death, with a major impact on the healthcare system. Genetic causes and different phenotypes are now increasingly being identified for this condition. In addition, specific medications, such as myosin inhibitors, have been recently shown as potentially able to modify its symptoms, hemodynamic abnormalities and clinical course. Our article aims to provide a comprehensive outline of the epidemiology, diagnosis and treatment of hypertrophic cardiomyopathy in the current era.

Case Report: Multiple types of arrhythmias in a late-confirmed Danon disease

Introduction

Danon disease is an X-linked disorder caused by pathogenic variants in lysosome-associated membrane protein 2 (LAMP2) gene, typically characterized by the triad of hypertrophic cardiomyopathy, myopathy, and intellectual disability. However, many patients may not present the typical presentation, especially in the early stage. Electrocardiogram (ECG) abnormalities can be found in almost all patients, with Wolff-Parkinson-White (WPW) syndrome being the most common. We reported the case of a 51-year-old woman who experienced multiple types of arrhythmias over three decades and was diagnosed with Danon disease late by genetic testing.

Case summary

A 51-year-old woman with a 36-year history of intermittent palpitations was admitted due to hemodynamically stable ventricular tachycardia (VT). Her past medical history revealed multiple arrhythmias and ECG abnormalities in her 30s and 40s, including WPW syndrome with paroxysmal supraventricular tachycardia, paroxysmal atrial flutter, atrial fibrillation, ventricular tachycardia, and complete left bundle branch block. She denied any family history of cardiovascular disease or sudden death. Upon arrival, her vital signs were unremarkable. Cardiovascular magnetic resonance (CMR) imaging revealed left ventricular enlargement and late gadolinium enhancement (LGE) in the anterior, inferior, and lateral walls. Subsequent, whole-exome sequencing (WES) gene testing revealed a pathogenic heterozygous variant in LAMP2 gene (c.696T>A; p.Cys232Ter), which confirmed the diagnosis of Danon disease.

Conclusion

Genetic testing should be considered in patients who display multiple arrhythmias with LV structural abnormalities of unknown etiology for a possible Danon disease.

Hypertrophic Cardiomyopathy and Ventricular Preexcitation in the Young: Cause and Accessory Pathway Characteristics

BACKGROUND

The cause of hypertrophic cardiomyopathy (HCM) in the young is highly varied. Ventricular preexcitation (preexcitation) is well recognized, yet little is known about the specificity for any cause and the characteristics of the responsible accessory pathways (AP).

METHODS

Retrospective cohort study of patients <21 years of age with HCM/preexcitation from 2000 to 2022. The cause of HCM was defined as isolated HCM, storage disorder, metabolic disease, or genetic syndrome. Atrioventricular AP (true AP) were distinguished from fasciculoventricular fibers (FVF) using standard invasive electrophysiology study criteria. AP were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in atrial fibrillation, shortest paced preexcited cycle length, or anterograde AP effective refractory period.

RESULTS

We identified 345 patients with HCM and 28 (8%) had preexcitation (isolated HCM, 10/220; storage disorder, 8/17; metabolic disease, 5/19; and genetic syndrome, 5/89). Six (21%) patients had clinical atrial fibrillation (1 with shortest preexcited RR interval <250 ms). Twenty-two patients underwent electrophysiology study which identified 23 true AP and 16 FVF. Preexcitation was exclusively FVF mediated in 8 (36%) patients. Five (23%) patients had AP with high-risk conduction properties (including ≥1 patient in each etiologic group). Multiple AP were seen in 8 (36%) and AP plus FVF in 10 (45%) patients. Ablation was acutely successful in 13 of 14 patients with recurrence in 3. One procedure was complicated by complete heart block after ablation of a high-risk midseptal AP. There were significant differences in QRS amplitude and delta wave amplitude between groups. There were no surface ECG features that differentiated AP from FVF.

CONCLUSIONS

Young patients with HCM and preexcitation have a high likelihood of underlying storage disease or metabolic disease. Nonisolated HCM should be suspected in young patients with large QRS and delta wave amplitudes. Surface ECG is not adequate to discriminate preexcitation from a benign FVF from that secondary to potentially life-threatening AP.

International Consensus on Differential Diagnosis and Management of Patients With Danon Disease: JACC State-of-the-Art Review

Danon disease is a rare X-linked autophagic vacuolar cardioskeletal myopathy associated with severe heart failure that can be accompanied with extracardiac neurologic, skeletal, and ophthalmologic manifestations. It is caused by loss of function variants in the LAMP2 gene and is among the most severe and penetrant of the genetic cardiomyopathies. Most patients with Danon disease will experience symptomatic heart failure. Male individuals generally present earlier than women and die of either heart failure or arrhythmia or receive a heart transplant by the third decade of life. Herein, the authors review the differential diagnosis of Danon disease, diagnostic criteria, natural history, management recommendations, and recent advances in treatment of this increasingly recognized and extremely morbid cardiomyopathy.

Clinical features of pediatric Danon disease and the importance of early diagnosis

Successful therapy in a cohort with early onset Danon disease (DD) highlights the potential importance of earlier disease recognition. We present experience from the largest National Pediatric Center in Russia for cardiomyopathy patients. This report focuses on identification of early clinical features of DD in the pediatric population by detailed pedigree analysis and review of medical records. RESULTS: Nine patients (3 females) were identified with DD at the Russian National Medical Research Center of Children's Health ("National Pediatric Center") aged birth to 16 years. At presentation/evaluation: all patients had left ventricular hypertrophy (LVH), ECG features of Wolff-Parkinson-White (WPW), and an increase in hepatic enzymes (particularly lactate dehydrogenase (LDH)); three had marked increase in NT-proBNP; two had HCM with impaired LV function; one had LVH with LV noncompaction; five had arrhythmia with paroxysmal supraventricular and/or ventricular tachycardia. Two teenagers died at ages 16-17 from refractory heart failure and two underwent heart transplantation. All patients were found to have a pathogenic/likely pathogenic variant in the LAMP2 gene, six patients had no family history and a de novo evolvement was documented in 4/6 of those available for genetic tested. Retrospective review related to family background and earlier clinical evaluations revealed a definitive or highly suspicious family history of DD in 3, early clinical presentation with cardiac abnormalities (ECG, echo) in 3, and cerebral, hepatic and/or neuromuscular symptoms in 5. Abnormalities were detected 9,5 months to 5,8 years, median 3,5 years prior to referral to the National Pediatric Center. CONCLUSION: The earliest clinical manifestations of Danon disease occur in the first 12 years of life with symptoms of skeletal muscle and cerebral disease, raised hepatic enzymes, and evidence of cardiac disease on ECG/echo.

The evolving paradigm and current perception of hypertrophic cardiomyopathy: Implications for management

Recent evidence from imaging and genetic screening studies has clearly shown that hypertrophic cardiomyopathy (HCM) is more common than initially perceived, emphasizing the need to reassess its associated clinical and social burden. While clinical and academic efforts have long been focused on stratification of arrhythmic risk and management of intraventricular obstruction, progression of cardiac dysfunction and heart failure-related complications have emerged as most relevant from the epidemiological standpoint, delineating a major unmet need. Furthermore, a broader perspective of our patients' needs has become central in the care of individuals with HCM, addressing issues that are not strictly clinical but equally important to their wellbeing, such as quality of life, athletic participation, lifestyle and reproductive choices and psychological adaptation to a chronic condition often detected at a young age. The appropriate evaluation and objective assessment of disease burden associated with HCM are increasingly relevant not only to management but also to trial design and evaluation of the efficacy of emerging, targeted treatments. In this review, we discuss the evolving perception of HCM prevalence and natural history, as well as recent acquisitions regarding its true, often under-appreciated socio-economic and clinical burden.

Clinical manifestations and MRI features of Danon disease: a case series

BACKGROUND

Danon disease (DD) is an exceptionally uncommon X-linked dominant lysosomal glycogen storage disorder characterized by pronounced ventricular hypertrophy and cardiac insufficiency. The timely identification of cardiac impairment in individuals with DD holds significant clinical importance.

CASE PRESENTATION

We present a case of Danon Disease in a three-generation pedigree from Anhui Province, China. Clinical features and laboratory data were collected and analyzed for a 16-year-old male proband (III-1) and two affected female family members (II-2 and II-3). The proband exhibited Wolf-Parkinson-White syndrome, hypertrophic cardiomyopathy, abnormal cognitive function, and muscle weakness. Gene sequencing confirmed a mutation (c.963G > A) in the LAMP-2 gene.

CONCLUSION

Patients with DD may present both dilated and hypertrophic cardiomyopathy. Comprehensive myocardial tissue characterization by MRI plays a key role in the diagnosis of the disease.

Genetic Abnormalities of the Sinoatrial Node and Atrioventricular Conduction

The peculiar electrophysiological properties of the sinoatrial node and the cardiac conduction system are key components of the normal physiology of cardiac impulse generation and propagation. Multiple genes and transcription factors and metabolic proteins are involved in their development and regulation. In this review, we have summarized the genetic underlying causes, key clinical findings, and the latest available clinical evidence. We will discuss clinical diagnosis and management of the genetic conditions associated with conduction disorders that are more prevalent in clinical practice, for this reason, very rare genetic diseases presenting sinus node or cardiac conduction system abnormalities are not discussed.

Advanced searching for hypertrophic cardiomyopathy heritability in real practice tomorrow

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease associated with morbidity and mortality at any age. As studies in recent decades have shown, the genetic architecture of HCM is quite complex both in the entire population and in each patient. In the rapidly advancing era of gene therapy, we have to provide a detailed molecular diagnosis to our patients to give them the chance for better and more personalized treatment. In addition to emphasizing the importance of genetic testing in routine practice, this review aims to discuss the possibility to go a step further and create an expanded genetic panel that contains not only variants in core genes but also new candidate genes, including those located in deep intron regions, as well as structural variations. It also highlights the benefits of calculating polygenic risk scores based on a combination of rare and common genetic variants for each patient and of using non-genetic HCM markers, such as microRNAs that can enhance stratification of risk for HCM in unselected populations alongside rare genetic variants and clinical factors. While this review is focusing on HCM, the discussed issues are relevant to other cardiomyopathies.

Opportunities and drawbacks of the subcutaneous defibrillator across different clinical settings

INTRODUCTION

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an established therapy for the prevention of sudden cardiac death (SCD) and an alternative to a transvenous implantable cardioverter-defibrillator system in selected patients. Beyond randomized clinical trials, many observational studies have described the clinical performance of S-ICD across different subgroups of patients.

AREAS COVERED

Our review aimed to describe the opportunities and drawbacks of the S-ICD, focusing on their use in special populations and across different clinical settings.

EXPERT OPINION

The choice to implant S-ICD should be based on the patient's tailored approach, which takes into account the adequate S-ICD screening at rest or during stress, the infective risk, the ventricular arrhythmia susceptibility, the progressive nature of the underlying disease, the work or sports activity, and the risk of lead-related complications.

Genetic causes of heart failure with preserved ejection fraction: emerging pharmacological treatments

Heart failure with preserved ejection fraction (HFpEF) is a major driver of cardiac morbidity and mortality in developed countries, due to ageing populations and the increasing prevalence of comorbidities. While heart failure with reduced ejection fraction is dominated by left ventricular impairment, HFpEF results from a complex interplay of cardiac remodelling, peripheral circulation, and concomitant features including age, hypertension, obesity, and diabetes. In an important subset, however, HFpEF is subtended by specific diseases of the myocardium that are genetically determined, have distinct pathophysiology, and are increasingly amenable to targeted, innovative treatments. While each of these conditions is rare, they collectively represent a relevant subset within HFpEF cohorts, and their prompt recognition has major consequences for clinical practice, as access to dedicated, disease-specific treatments may radically change the quality of life and outcome. Furthermore, response to standard heart failure treatment will generally be modest for these individuals, whose inclusion in registries and trials may dilute the perceived efficacy of treatments targeting mainstream HFpEF. Finally, a better understanding of the molecular underpinnings of monogenic myocardial disease may help identify therapeutic targets and develop innovative treatments for selected HFpEF phenotypes of broader epidemiological relevance. The field of genetic cardiomyopathies is undergoing rapid transformation due to recent, groundbreaking advances in drug development, and deserves greater awareness within the heart failure community. The present review addressed existing and developing therapies for genetic causes of HFpEF, including hypertrophic cardiomyopathy, cardiac amyloidosis, and storage diseases, discussing their potential impact on management and their broader implications for our understanding of HFpEF at large.

Clinical features of Danon disease and insights gained from LAMP-2 deficiency models

Danon disease (DD) is an X-linked multisystem disorder with clinical features characterized by the triad of hypertrophic cardiomyopathy, skeletal muscle weakness, and mental retardation. Cardiac involvement can be fatal in the absence of an effective treatment option such as heart transplantation. Molecular studies have proved that LAMP-2 protein deficiency, mainly LAMP-2B isoform, resulting from LAMP2 gene mutation, is the culprit for DD. Autophagy impairment due to LAMP-2 deficiency mediated the accumulation of abnormal autophagic vacuoles in cells. While it is not ideal for mimicking DD phenotypes in humans, the emergence of LAMP-2-deficient animal models and induced pluripotent stem cells from DD patients provided powerful tools for exploring DD mechanism. In both in vitro and in vivo studies, much evidence has demonstrated that mitochondria dysfunction and fragmentation can result in DD pathology. Fundamental research contributes to the therapeutic transformation. By targeting the molecular core, several potential therapies have demonstrated promising results in partial phenotypes improvement. Among them, gene therapies anticipate inaugurate a class of symptom control and prevention drugs as their in vivo effects are promising, and one clinical trial is currently underway.

Clinical profile and outcome of cardiomyopathies in infants and children seen at a tertiary centre

INTRODUCTION

Due to their rare prevalence and marked heterogeneity, pediatric cardiomyopathies (CMPs) are little known and scarcely reported. We report the etiology, clinical profile and outcome of a consecutive cohort of children diagnosed with CMP and followed at Meyer Children's Hospital over a decade.

PATIENTS AND METHODS

We retrospectively reviewed patients consecutively referred from May 2008 to May 2019 for pediatric onset CMP (<18 years). Heart disease caused by arrhythmic disorders, toxic agents, rheumatic conditions and maternal disease were excluded.

RESULTS

We enrolled 110 patients (65 males), diagnosed at a median age of 27 [4-134] months; 35% had an infant onset (<1 year of age). A positive family history was more often associated with childhood-onset (38.8%). Hypertrophic cardiomyopathy (HCM; 48 patients) was the most frequent phenotype, followed by dilated cardiomyopathy (DCM; 35 patients). While metabolic and idiopathic etiologies were preponderant in infants, metabolic and sarcomeric diseases were most frequent in the childhood-onset group. Major adverse cardiac events (MACE) occurred in 31.8% of patients, including hospitalization for acute heart failure in 25.5% of patients, most commonly due to DCM. Overall, the most severe outcomes were documented in patients with metabolic diseases.

CONCLUSIONS

In a consecutive cohort of pediatric patients with CMP, those with infantile onset and with a metabolic etiology had the worst prognosis. Overall, MACE occurred in 41% of the entire population, most commonly associated with DCM, inborn errors of metabolism and genetic syndromes. Systematic NGS genetic testing was critical for etiological diagnosis and management.

Genetic Basis of Childhood Cardiomyopathy

BACKGROUND

The causes of cardiomyopathy in children are less well described than in adults. We evaluated the clinical diagnoses and genetic causes of childhood cardiomyopathy and outcomes of cascade genetic testing in family members.

METHODS

We recruited children from a pediatric cardiology service or genetic heart diseases clinic. We performed Sanger, gene panel, exome or genome sequencing and classified variants for pathogenicity using American College of Molecular Genetics and Genomics guidelines.

RESULTS

Cardiomyopathy was diagnosed in 221 unrelated children aged ≤18 years. Children mostly had hypertrophic cardiomyopathy (n=98, 44%) or dilated cardiomyopathy (n=89, 40%). The highest genetic testing diagnostic yields were in restrictive cardiomyopathy (n=16, 80%) and hypertrophic cardiomyopathy (n=65, 66%), and lowest in dilated cardiomyopathy (n=26, 29%) and left ventricular noncompaction (n=3, 25%). Pathogenic variants were primarily found in genes encoding sarcomere proteins, with TNNT2 and TNNI3 variants associated with more severe clinical outcomes. Ten children (4.5%) had multiple pathogenic variants. Genetic test results prompted review of clinical diagnosis in 14 families with syndromic, mitochondrial or metabolic gene variants. Cascade genetic testing in 127 families confirmed 24 de novo variants, recessive inheritance in 8 families, and supported reclassification of 12 variants.

CONCLUSIONS

Genetic testing of children with cardiomyopathy supports a precise clinical diagnosis, which may inform prognosis.

Beyond Sarcomeric Hypertrophic Cardiomyopathy: How to Diagnose and Manage Phenocopies

PURPOSE OF REVIEW

We describe the most common phenocopies of hypertrophic cardiomyopathy, their pathogenesis, and clinical presentation highlighting similarities and differences. We also suggest a step-by-step diagnostic work-up that can guide in differential diagnosis and management.

RECENT FINDINGS

In the last years, a wider application of genetic testing and the advances in cardiac imaging have significantly changed the diagnostic approach to HCM phenocopies. Different prognosis and management, with an increasing availability of disease-specific therapies, make differential diagnosis mandatory. The HCM phenotype can be the cardiac manifestation of different inherited and acquired disorders presenting different etiology, prognosis, and treatment. Differential diagnosis requires a cardiomyopathic mindset allowing to recognize red flags throughout the diagnostic work-up starting from clinical and family history and ending with advanced imaging and genetic testing. Different prognosis and management, with an increasing availability of disease-specific therapies make differential diagnosis mandatory.

Case Report: Danon Disease: Six Family Members and Literature Review

Danon disease is a rare X-linked dominant genetic disorder that manifests with a clinical triad of cardiomyopathy, skeletal myopathy, and intellectual disability. It is caused by mutations in the lysosome-associated membrane 2 (LAMP2) gene. We report one case of Danon disease and his family members, characterized by ventricular pre-excitation, ventricular hypertrophy, abnormal muscle enzymes, and aberrant liver function. All the patients were confirmed to have Danon disease through genetic screening. Relevant literature was reviewed as a reference for the diagnosis and treatment of the disease.

Sex-Related Differences in Genetic Cardiomyopathies

Cardiomyopathies are a heterogeneous collection of diseases that have in common primary functional and structural abnormalities of the heart muscle, often genetically determined. The most effective categorization of cardiomyopathies is based on the presenting phenotype, with hypertrophic, dilated, arrhythmogenic, and restrictive cardiomyopathy as the prototypes. Sex modulates the prevalence, morpho-functional manifestations and clinical course of cardiomyopathies. Aspects as diverse as ion channel expression and left ventricular remodeling differ in male and female patients with myocardial disease, although the reasons for this are poorly understood. Moreover, clinical differences may also result from complex societal/environmental discrepancies between sexes that may disadvantage women. This review provides a state-of-the-art appraisal of the influence of sex on cardiomyopathies, highlighting the many gaps in knowledge and open research questions.

Hypokinetic hypertrophic cardiomyopathy: clinical phenotype, genetics, and prognosis

Aims

To describe the phenotype, genetics, and events associated with the development of hypertrophic cardiomyopathy (HCM) with reduced ventricular function (HCMr). Heart failure in HCM is usually associated with preserved ejection fraction, yet some HCM patients develop impaired systolic function that is associated with worse outcomes.

Methods and results

Our registry included 1328 HCM patients from two centres in Spain and Israel. Patients with normal baseline ventricular function were matched, and a competing‐risk analysis was performed to find factors associated with HCMr development. Patient records were reviewed to recognize clinically significant events that occurred closely before the development of HCMr. Genetic data were collected in patients with HCMr. A composite of all‐cause mortality or ventricular assist device (VAD)/heart transplantation was assessed according to ventricular function. Median age was 56, and 34% were female patients. HCMr at evaluation was seen in 37 (2.8%) patients, and 46 (3.5%) developed HCMr during median follow up of 9 years. HCMr was associated with younger age of diagnosis, poor functional class, and ventricular arrhythmia. Atrial fibrillation, pacemaker implantation, and baseline left ventricular ejection fraction (LVEF) of ≤55% were significant predictors of future HCMr development, while LV obstruction predicted a lower risk. Genetic testing performed in 53 HCMr patients, identifying one or more pathogenic variant in 38 (72%): most commonly in myosin binding protein C (n = 20). Six of these patients had an additional pathogenic variant in one of the sarcomere genes. Patients with baseline HCMr had a higher risk (hazard ratio 6.4, 4.1–10.1) for the composite outcome and for the individual components. Patients who developed HCMr in the course of the study had similar mortality but a higher rate of VAD/heart transplantation compared with HCM with normal LVEF.

Conclusions

Hypertrophic cardiomyopathy with reduced ejection fraction is associated with heart failure and poor outcome. Arrhythmia, cardiac surgery, and device implantation were commonly documented prior to HCMr development, suggesting they may be either a trigger or the result of adverse remodelling. Future studies should focus on prediction and prevention of HCMr.

Diagnosis and Management of Rare Cardiomyopathies in Adult and Paediatric Patients. A Position Paper of the Italian Society of Cardiology (SIC) and Italian Society of Paediatric Cardiology (SICP)

Cardiomyopathies (CMPs) are myocardial diseases in which the heart muscle is structurally and functionally abnormal in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Thought for a long time to be rare diseases, it is now clear that most of the CMPs can be easily observed in clinical practice. However, there is a group of specific heart muscle diseases that are rare in nature whose clinical/echocardiographic phenotypes resemble those of the four classical morphological subgroups of hypertrophic, dilated, restrictive, arrhythmogenic CMPs. These rare CMPs, often but not solely diagnosed in infants and paediatric patients, should be more properly labelled as specific CMPs. Emerging consensus exists that these conditions require tailored investigation and management. Indeed, an appropriate understanding of these conditions is mandatory for early treatment and counselling. At present, however, the multisystemic and heterogeneous presentation of these entities is a challenge for clinicians, and time delay in diagnosis is a significant concern. The aim of this paper is to define practical recommendations for diagnosis and management of the rare CMPs in paediatric or adult age. A modified Delphi method was adopted to grade the recommendations proposed by each member of the writing committee.

Whole genome sequencing delineates regulatory, copy number, and cryptic splice variants in early onset cardiomyopathy

Cardiomyopathy (CMP) is a heritable disorder. Over 50% of cases are gene-elusive on clinical gene panel testing. The contribution of variants in non-coding DNA elements that result in cryptic splicing and regulate gene expression has not been explored. We analyzed whole-genome sequencing (WGS) data in a discovery cohort of 209 pediatric CMP patients and 1953 independent replication genomes and exomes. We searched for protein-coding variants, and non-coding variants predicted to affect the function or expression of genes. Thirty-nine percent of cases harbored pathogenic coding variants in known CMP genes, and 5% harbored high-risk loss-of-function (LoF) variants in additional candidate CMP genes. Fifteen percent harbored high-risk regulatory variants in promoters and enhancers of CMP genes (odds ratio 2.25, p = 6.70 × 10-7 versus controls). Genes involved in α-dystroglycan glycosylation (FKTN, DTNA) and desmosomal signaling (DSC2, DSG2) were most highly enriched for regulatory variants (odds ratio 6.7-58.1). Functional effects were confirmed in patient myocardium and reporter assays in human cardiomyocytes, and in zebrafish CRISPR knockouts. We provide strong evidence for the genomic contribution of functionally active variants in new genes and in regulatory elements of known CMP genes to early onset CMP.

Cardiomyopathies in Children and Systemic Disorders When Is It Useful to Look beyond the Heart?

Cardiomyopathy (CMP) is a rare disease in the pediatric population, with a high risk of morbidity and mortality. The genetic etiology of CMPs in children is extremely heterogenous. These two factors play a major role in the difficulties of establishing standard diagnostic and therapeutic protocols. Isolated CMP in children is a frequent finding, mainly caused by sarcomeric gene variants with a detection rate that can reach up to 50% of analyzed cohorts. Complex multisystemic forms of pediatric CMP are even more heterogenous. Few studies in literature take into consideration this topic as the main core since it represents a rarity (systemic CMP) within a rarity (pediatric population CMP). Identifying etiology in this cohort is essential for understanding prognosis, risk stratification, eligibility to heart transplantation and/or mechanical-assisted procedures, preventing multiorgan complications, and relatives' recurrence risk calculation. The previous points represent a cornerstone in patients' empowerment and personalized medical care approach. The aim of this work is to propose a new approach for an algorithm in the setting of the diagnostic framework of systemic pediatric CMP. On the other hand, during the literature review, we noticed a relatively common etiologic pattern in some forms of complex/multisystem CMP. In other words, certain syndromes such as Danon, Vici, Alström, Barth, and Myhre syndrome share a common pathway of directly or indirectly defective "autophagy" process, which appears to be a possible initiating/triggering factor for CMPs. This conjoint aspect could be important for possible prognostic/therapeutic implications in this category of patients. However, multicentric studies detailed functional and experimental models are needed prior to deriving conclusions.

Natural history of left ventricular hypertrophy in infants of diabetic mothers

BACKGROUND

This study sought to describe the characteristics and the natural course of left ventricular hypertrophy (LVH) in a well-characterized consecutive cohort of infants of diabetic mothers (IDMs).

METHODS

Sixty consecutive IDMs with LVH have been retrospectively identified and enrolled in the study. All IDMs were evaluated at baseline and every 6 months until LV wall thickness regression, defined as the decrease of wall thickness measurement into the normal reference range for cardiac parameters (z-score > -2 and < 2). A comprehensive assessment was performed in those patients with diagnostic markers suggestive of a different cause and/or without significant reduction of the LVH during follow-up.

RESULTS

At 1-year follow-up, all IDMs showed a significant reduction of maximal wall thickness MWT (6.00 mm [IQR 5.00-712] vs. 5.50 mm [IQR 5.00-6.00], p-value <0.001; MWT-z-score: 4.86 [IQR 3.93-7.61] vs. 1.72 [IQR 1.08-2.85], p-value <0.001) compared to baseline, and all patients showed LV wall thickness regression or residual mild or moderate LVH (57%, 28%, and 12%, respectively), except 2 patients with persistent severe LVH, that after a comprehensive clinical-genetic assessment were diagnosed as Noonan syndrome with multiple lentigines. At multivariate analysis, MWT was negatively associated with LV wall thickness regression at 1-year follow-up (MWT-mm: OR 0.48[0.29-0.79], p-value = 0.004; MWT-z-score: OR 0.71[0.56-0.90], p-value = 0.004).

CONCLUSIONS

LVH in IDMs represents a benign condition with complete regression during the first years of life. In those patients without LV wall thickness regression, combined with clinical markers suggesting a specific disease, a complete work-up is required for a definite diagnosis.

The Influence of Genotype on the Phenotype, Clinical Course, and Risk of Adverse Events in Children with Hypertrophic Cardiomyopathy

Genetic testing in children with hypertrophic cardiomyopathy (HCM) can modify clinical management and lifestyle counseling. However, predicting long-term outcome and response to management in individual patients remains challenging, because of the peculiar genetic heterogeneity of the disease in the pediatric age range. Children with HCM secondary to an inborn error of metabolism or malformation syndromes tend to have a worse outcome compared with those with the classic sarcomeric form. Among the latter, adverse genetic features are represented by the identification of a pathogenic variant in MYH7, often associated with severe hypertrophy, a complex genotype, or a de novo variant.

Genetic Abnormalities of the Sinoatrial Node and Atrioventricular Conduction

The peculiar electrophysiological properties of the sinoatrial node and the cardiac conduction system are key components of the normal physiology of cardiac impulse generation and propagation. Multiple genes and transcription factors and metabolic proteins are involved in their development and regulation. In this review, we have summarized the genetic underlying causes, key clinical findings, and the latest available clinical evidence. We will discuss clinical diagnosis and management of the genetic conditions associated with conduction disorders that are more prevalent in clinical practice, for this reason, very rare genetic diseases presenting sinus node or cardiac conduction system abnormalities are not discussed.

Pediatric Restrictive Cardiomyopathies

Restrictive cardiomyopathy (RCM) is the least frequent phenotype among pediatric heart muscle diseases, representing only 2.5-3% of all cardiomyopathies diagnosed during childhood. Pediatric RCM has a poor prognosis, high incidence of pulmonary hypertension (PH), thromboembolic events, and sudden death, is less amenable to medical or surgical treatment with high mortality rates. In this scenario, heart transplantation remains the only successful therapeutic option. Despite a shared hemodynamic profile, characterized by severe diastolic dysfunction and restrictive ventricular filling, with normal ventricle ejection fraction and wall thickness, RCM recognizes a broad etiological spectrum, consisting of genetic/familial and acquired causes, each of which has a distinct pathophysiology and natural course. Hence, the aim of this review is to cover the causes, clinical presentation, diagnostic evaluation, treatment, and prognosis of pediatric RCM.

Hypertrophic Cardiomyopathy in Children: Pathophysiology, Diagnosis, and Treatment of Non-sarcomeric Causes

Hypertrophic cardiomyopathy (HCM) is a myocardial disease characterized by left ventricular hypertrophy not solely explained by abnormal loading conditions. Despite its rare prevalence in pediatric age, HCM carries a relevant risk of mortality and morbidity in both infants and children. Pediatric HCM is a large heterogeneous group of disorders. Other than mutations in sarcomeric genes, which represent the most important cause of HCM in adults, childhood HCM includes a high prevalence of non-sarcomeric causes, including inherited errors of metabolism (i.e., glycogen storage diseases, lysosomal storage diseases, and fatty acid oxidation disorders), malformation syndromes, neuromuscular diseases, and mitochondrial disease, which globally represent up to 35% of children with HCM. The age of presentation and the underlying etiology significantly impact the prognosis of children with HCM. Moreover, in recent years, different targeted approaches for non-sarcomeric etiologies of HCM have emerged. Therefore, the etiological diagnosis is a fundamental step in designing specific management and therapy in these subjects. The present review aims to provide an overview of the non-sarcomeric causes of HCM in children, focusing on the pathophysiology, clinical features, diagnosis, and treatment of these rare disorders.