Cardiac Involvement in Women With Pathogenic Dystrophin Gene Variants

Failure to Resolve Inflammation Contributes to Juvenile-Onset Cardiomyopathy in a Mouse Model of Duchenne Muscular Dystrophy

The absence of dystrophin protein causes cardiac dysfunction in boys with Duchenne Muscular Dystrophy (DMD). However, the common mouse model of DMD (B10-mdx) does not manifest cardiac deficits until late adulthood limiting our understanding of the mechanism and therapeutic approaches to target the pediatric-onset cardiac pathology in DMD. We show the mdx mouse model on the DBA/2J genetic background (D2-mdx) displays juvenile-onset cardiomyopathy. Molecular and histological analysis revealed heightened leukocyte chemotactic signaling and failure to resolve inflammation, leading to chronic inflammation and extracellular matrix (ECM) fibrosis, causing cardiac pathology in juvenile D2-mdx mice. We show that pharmacologically activating the N-formyl peptide receptor 2 (FPR2) - a receptor that physiologically resolves acute inflammation, mitigated chronic cardiac inflammation and fibrosis, and prevented juvenile onset cardiomyopathy in the D2-mdx mice. These studies offer insights into pediatric onset of cardiac damage in DMD, a new therapeutic target, and identify a drug-based potential therapy.

Systemic Treatment of Body-Wide Duchenne Muscular Dystrophy Symptoms

Duchenne muscular dystrophy (DMD) is a fatal X-linked disease that leads to premature death due to the loss of dystrophin. Current strategies predominantly focus on the therapeutic treatment of affected skeletal muscle tissue. However, certain results point to the fact that with successful treatment of skeletal muscle, DMD-exposed latent phenotypes in tissues, such as cardiac and smooth muscle, might lead to adverse effects and even death. Likewise, it is now clear that the absence of dystrophin affects the function of the nervous system, and that this phenotype is more pronounced when shorter dystrophins are absent, in addition to the full-length dystrophin that is present predominantly in the muscle. Here, I focus on the systemic aspects of DMD, highlighting the ubiquitous expression of the dystrophin gene in human tissues. Furthermore, I describe therapeutic strategies that have been tested in the clinic and point to unresolved questions regarding the function of distinct dystrophin isoforms, and the possibility of current therapeutic strategies to tackle phenotypes that relate to their absence.

Genetic counseling for the dystrophinopathies-Practice resource of the National Society of Genetic Counselors

The dystrophinopathies encompass the phenotypically variable forms of muscular dystrophy caused by pathogenic variants in the DMD gene. The dystrophinopathies include the most common inherited muscular dystrophy among 46,XY individuals, Duchenne muscular dystrophy, as well as Becker muscular dystrophy and other less common phenotypic variants. With increased access to and utilization of genetic testing in the diagnostic and carrier setting, genetic counselors and clinicians in diverse specialty areas may care for individuals with and carriers of dystrophinopathy. This practice resource was developed as a tool for genetic counselors and other health care professionals to support counseling regarding dystrophinopathies, including diagnosis, health risks and management, psychosocial needs, reproductive options, clinical trials, and treatment. Genetic testing efforts have enabled genotype/phenotype correlation in the dystrophinopathies, but have also revealed unexpected findings, further complicating genetic counseling for this group of conditions. Additionally, the therapeutic landscape for dystrophinopathies has dramatically changed with several FDA-approved therapeutics, an expansive research pathway, and numerous clinical trials. Genotype-phenotype correlations are especially complex and genetic counselors' unique skill sets are useful in exploring and explaining this to families. Given the recent advances in diagnostic testing and therapeutics related to dystrophinopathies, this practice resource is a timely update for genetic counselors and other healthcare professionals involved in the diagnosis and care of individuals with dystrophinopathies.

Arrhythmias and cardiac MRI associations in patients with established cardiac dystrophinopathy

AIMS

Some patients with cardiac dystrophinopathy die suddenly. Whether such deaths are preventable by specific antiarrhythmic management or simply indicate heart failure overwhelming medical therapies is uncertain. The aim of this prospective, cohort study was to describe the occurrence and nature of cardiac arrhythmias recorded during prolonged continuous ECG rhythm surveillance in patients with established cardiac dystrophinopathy and relate them to abnormalities on cardiac MRI.

METHODS AND RESULTS

A cohort of 10 patients (36.3 years; 3 female) with LVEF<40% due to Duchenne (3) or Becker muscular (4) dystrophy or Duchenne muscular dystrophy-gene carrying effects in females (3) were recruited, had cardiac MRI, ECG signal-averaging and ECG loop-recorder implants. All were on standard of care heart medications and none had prior history of arrhythmias.No deaths or brady arrhythmias occurred during median follow-up 30 months (range 13-35). Self-limiting episodes of asymptomatic tachyarrhythmia (range 1-29) were confirmed in 8 (80%) patients (ventricular only 2; ventricular and atrial 6). Higher ventricular arrhythmia burden correlated with extent of myocardial fibrosis (extracellular volume%, p=0.029; native T1, p=0.49; late gadolinium enhancement, p=0.49), but not with LVEF% (p=1.0) on MRI and atrial arrhythmias with left atrial dilatation. Features of VT episodes suggested various underlying arrhythmia mechanisms.

CONCLUSIONS

The overall prevalence of arrhythmias was low. Even in such a small sample size, higher arrhythmia counts occurred in those with larger scar burden and greater ventricular volume, suggesting key roles for myocardial stretch as well as disease progression in arrhythmogenesis. These features overlap with the stage of left ventricular dysfunction when heart failure also becomes overt. The findings of this pilot study should help inform the design of a definitive study of specific antiarrhythmic management in dystrophinopathy.

TRIAL REGISTRATION NUMBER

ISRCTN15622536.

Heart in Disguise: Unmasking a Novel Gene Deletion in Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is an underrecognized condition with a myriad of etiologies, but it is often labeled idiopathic. However, genetic mutations are emerging as a more common cause of idiopathic DCM than previously believed. Herein, we present a case of a previously healthy 45-year-old woman who presented with three weeks of exertional dyspnea and orthopnea. An echocardiogram showed DCM with severely reduced systolic function and diastolic dysfunction. She was extensively worked up for potential etiologies of her heart failure which included HIV testing, parasite smear, viral serologies, autoimmune testing, cardiac MRI for infiltrative diseases, and coronary catheterization. She was ultimately tested for genetic mutations which revealed a 49-51 exon deletion of the dystrophin (Duchenne muscular dystrophy (DMD)) gene. This case highlights the guideline-based evaluation and management of new-onset heart failure in a healthy 45-year-old female without known predisposing risk factors or family history. It also sheds light on the expansive genetic etiologies that have only recently been identified in those with idiopathic cardiomyopathy. Further research is crucial to improve our understanding of genetic associations of cardiomyopathy.

The Early Care (0-3 Years) In Duchenne Muscular Dystrophy Meeting Report

Objective

This report summarizes the key discussions from the "Early Care (0-3 years) in Duchenne Muscular Dystrophy" meeting, which aimed to address the challenges and opportunities in the diagnosis and care of Duchenne muscular dystrophy (DMD) and female carriers within the 0-3-year age group.

Methods

The meeting brought together experts and healthcare providers who shared insights, discussed advancements in DMD care, and identified research needs. Presentations covered diagnostic challenges, approved therapies, clinical trials, identification of young female carriers, and the importance of clinical care and support for families.

Results

The meeting highlighted the importance of timely diagnosis and the lack of evidence-based guidelines for the care of children with DMD aged 0-3 years. Diagnostic challenges were discussed, including delays in receiving a DMD diagnosis and disparities based on ethnicity. The potential benefits and process of newborn screening were addressed.Approved therapeutic interventions, such as corticosteroids and exon-skipping drugs, were explored, with studies indicating the potential benefits of early initiation of corticosteroid therapy and the safety of exon-skipping drugs in DMD. Clinical trials involving infants and young boys were discussed, focusing on drugs like ataluren, vamorolone, and gene therapies.The meeting emphasized the importance of clinical care and support for families, including comprehensive information provision, early intervention services, and individualized support. The identification and care of young female carriers were also addressed.

Conclusion

The meeting provided a platform for experts and healthcare providers to discuss and identify key aspects of early care for children with DMD aged 0-3 years. The meeting emphasized the need for early diagnosis, evidence-based guidelines, and comprehensive care and support for affected children and their families. Further research, collaboration, and the development of consensus guidelines are needed to improve early diagnosis, treatment, and outcomes in this population.

Myocardial native T1 mapping and extracellular volume quantification in asymptomatic female carriers of Duchenne muscular dystrophy gene mutations

BACKGROUND

Female carriers of dystrophin gene mutations (DMD-FC) were previously considered non-manifesting, but in recent decades, cardiomyopathy associated with muscular dystrophy and myocardial fibrosis has been described. Our study aimed to assess prospectively myocardial fibrosis in asymptomatic DMD-FC compared to a sex-matched control group (CG) with similar age distribution using native T1 mapping and extracellular volume (ECV) quantification by cardiovascular magnetic resonance (CMR) imaging.

MATERIALS AND METHODS

38 DMD-FC with verified genetic mutation and 22 healthy volunteers were included. Using CMR, native T1 relaxation time and ECV quantification were determined in each group. Late gadolinium enhancement (LGE) was assessed in all cases.

RESULTS

There were 38 DMD-FC (mean age 39.1 ± 8.8 years) and 22 healthy volunteers (mean age 39.9 ± 12.6 years) imagined by CMR. The mean global native T1 relaxation time was similar for DMD-FC and CG (1005.1 ± 26.3 ms vs. 1003.5 ± 25.0 ms; p-value = 0.81). Likewise, the mean global ECV value was also similar between the groups (27.92 ± 2.02% vs. 27.10 ± 2.89%; p-value = 0.20). The segmental analysis of mean ECV values according to the American Heart Association classification did not show any differences between DMD-FC and CG. There was a non-significant trend towards higher mean ECV values of DMD-FC in the inferior and inferolateral segments of the myocardium (p-value = 0.075 and 0.070 respectively).

CONCLUSION

There were no statistically significant differences in the mean global and segmental native T1 relaxation times and the mean global or segmental ECV values. There was a trend towards higher segmental mean ECV values of DMD-FC in the inferior and inferolateral walls of the myocardium.

Long-term outcomes for females with early-onset dystrophinopathy

AIM

To study long-term disease course for females with early-onset dystrophinopathy, including common (female) symptoms, challenges in social participation, the need for care, and current healthcare management to support guideline development.

METHOD

Twelve females with early-onset dystrophinopathy were followed for a median period of more than 17 years (range 1-36).

RESULTS

One patient died owing to end-stage cardiac failure. Cardiac abnormalities were observed in three of the remaining 11 participants. Respiratory function was reduced in seven of 10 participants. Fatigue, myalgia, lower back pain, and arthralgia were reported in more than six of the participants. Functional status varied from exercise intolerance to wheelchair dependency. Most or all of the 10 participants reported restrictions in participation in work (n = 10), household duties (n = 10), sports (n = 9), and education (n = 8). Only a few participants received followed-up pulmonary (n = 2) or rehabilitation (n = 3) care.

INTERPRETATION

Females with early-onset dystrophinopathy experience a wide range of impairments, comorbidities, limitations in activities, and restrictions in social participation. The whole spectrum should be acknowledged in the healthcare setting. Neuromuscular and cardiac follow-up are indispensable. Additional respiratory assessment and rehabilitation care are expected to improve health status and support daily activities and participation.

WHAT THIS PAPER ADDS

No standard diagnostic procedures seem to exist for female patients suspected for dystrophinopathy. Female participants with early-onset dystrophinopathy experienced a broad scope of burdening symptoms, such as fatigue, myalgia, lower back pain, and arthralgia. None of participants worked full time, all felt restricted in paid work, and most felt restricted in education. Most participants showed decreased lung function, while only one was symptomatic. Availability of rehabilitation care may improve support for daily activities and participation for females with early-onset dystrophinopathy.

Real-World Results from Combined Screening for Monogenic Genomic Health Risks and Reproductive Risks in 300 Adults

New methods and demonstrations of feasibility guide future implementation of genomic population health screening programs. This is the first report of genomic population screening in a primary care, non-research setting using existing large carrier and health risk gene sequencing panels combined into one 432-gene test that is offered to adults of any health status. This report summarizes basic demographic data and analyses patterns of pathogenic and likely pathogenic genetic findings for the first 300 individuals tested in this real-world scenario. We devised a classification system for gene results to facilitate clear message development for our Genomic Medicine Action Plan messaging tool used to summarize and activate results for patients and primary care providers. Potential genetic health risks of various magnitudes for a broad range of disorders were identified in 16% to 34% of tested individuals. The frequency depends on criteria used for the type and penetrance of risk. 86% of individuals are carriers for one or more recessive diseases. Detecting, reporting, and guiding response to diverse genetic health risks and recessive carrier states in a single primary care genomic screening test appears feasible and effective. This is an important step toward exploring an exome or genome sequence as a multi-purpose clinical screening tool.

Newborn screening for Duchenne muscular dystrophy-early detection and diagnostic algorithm for female carriers of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common pediatric-onset form of muscular dystrophy, occurring in 1 in 5,000 live male births. DMD is a multi-system disease resulting in muscle weakness with progressive deterioration of skeletal, heart, and smooth muscle, and learning disabilities. Pathogenic/likely pathogenic (P/LP) variants in the DMD gene, which encodes dystrophin protein, cause dystrophinopathy. All males with a P/LP variant in the X-linked DMD gene are expected to be affected. Two to 20% of female heterozygotes with a P/LP variant develop symptoms of dystrophinopathy ranging from mild muscle weakness to significant disability similar to Becker muscular dystrophy. Recently, with improvements in therapies and testing methodology, there is stronger evidence supporting newborn screening (NBS) for DMD for males and females because females may also develop symptoms. A consented pilot study to screen newborns for DMD was initiated in New York State (NYS) and conducted from 2019 to 2021. The identification of female carriers and the realization of the subsequent uncertainty of providers concerning follow-up during the pilot led to the development of algorithms for screening and diagnosis of carrier females, including both NBS and cascade molecular testing of family members.