The screening for X-linked Emery-Dreifuss muscular dystrophy amongst young patients with idiopathic heart conduction system disease treated by a pacemaker implant

Genotype-Phenotype Correlations in Human Diseases Caused by Mutations of LINC Complex-Associated Genes: A Systematic Review and Meta-Summary

Mutations in genes encoding proteins associated with the linker of nucleoskeleton and cytoskeleton (LINC) complex within the nuclear envelope cause different diseases with varying phenotypes including skeletal muscle, cardiac, metabolic, or nervous system pathologies. There is some understanding of the structure of LINC complex-associated proteins and how they interact, but it is unclear how mutations in genes encoding them can cause the same disease, and different diseases with different phenotypes. Here, published mutations in LINC complex-associated proteins were systematically reviewed and analyzed to ascertain whether patterns exist between the genetic sequence variants and clinical phenotypes. This revealed LMNA is the only LINC complex-associated gene in which mutations commonly cause distinct conditions, and there are no clear genotype-phenotype correlations. Clusters of LMNA variants causing striated muscle disease are located in exons 1 and 6, and metabolic disease-associated LMNA variants are frequently found in the tail of lamin A/C. Additionally, exon 6 of the emerin gene, EMD, may be a mutation "hot-spot", and diseases related to SYNE1, encoding nesprin-1, are most often caused by nonsense type mutations. These results provide insight into the diverse roles of LINC-complex proteins in human disease and provide direction for future gene-targeted therapy development.

2022 HRS expert consensus statement on evaluation and management of arrhythmic risk in neuromuscular disorders

This international multidisciplinary document is intended to guide electrophysiologists, cardiologists, other clinicians, and health care professionals in caring for patients with arrhythmic complications of neuromuscular disorders (NMDs). The document presents an overview of arrhythmias in NMDs followed by detailed sections on specific disorders: Duchenne muscular dystrophy, Becker muscular dystrophy, and limb-girdle muscular dystrophy type 2; myotonic dystrophy type 1 and type 2; Emery-Dreifuss muscular dystrophy and limb-girdle muscular dystrophy type 1B; facioscapulohumeral muscular dystrophy; and mitochondrial myopathies, including Friedreich ataxia and Kearns-Sayre syndrome, with an emphasis on managing arrhythmic cardiac manifestations. End-of-life management of arrhythmias in patients with NMDs is also covered. The document sections were drafted by the writing committee members according to their area of expertise. The recommendations represent the consensus opinion of the expert writing group, graded by class of recommendation and level of evidence utilizing defined criteria. The recommendations were made available for public comment; the document underwent review by the Heart Rhythm Society Scientific and Clinical Documents Committee and external review and endorsement by the partner and collaborating societies. Changes were incorporated based on these reviews. By using a breadth of accumulated available evidence, the document is designed to provide practical and actionable clinical information and recommendations for the diagnosis and management of arrhythmias and thus improve the care of patients with NMDs.

Case Reports: Emery-Dreifuss Muscular Dystrophy Presenting as a Heart Rhythm Disorders in Children

Emery-Dreifuss muscular dystrophy (EDMD) is inherited muscle dystrophy often accompanied by cardiac abnormalities in the form of supraventricular arrhythmias, conduction defects and sinus node dysfunction. Cardiac phenotype typically arises years after skeletal muscle presentation, though, could be severe and life-threatening. The defined clinical manifestation with joint contractures, progressive muscle weakness and atrophy, as well as cardiac symptoms are observed by the third decade of life. Still, clinical course and sequence of muscle and cardiac signs may be variable and depends on the genotype. Cardiac abnormalities in patients with EDMD in pediatric age are not commonly seen. Here we describe five patients with different forms of EDMD (X-linked and autosomal-dominant) caused by the mutations in EMD and LMNA genes, presented with early onset of cardiac abnormalities and no prominent skeletal muscle phenotype. The predominant forms of cardiac pathology were atrial arrhythmias and conduction disturbances that progress over time. The presented cases discussed in the light of therapeutic strategy, including radiofrequency ablation and antiarrhythmic devices implantation, and the importance of thorough neurological and genetic screening in pediatric patients presenting with complex heart rhythm disorders.

Neuromuscular Disease: Cardiac Manifestations and Sudden Death Risk

Cardiovascular complications of neuromuscular diseases disproportionately affect the cardiac conduction system. Cardiomyopathy and cardiac arrhythmias produce significant morbidity and mortality. Patients with neuromuscular diseases should be carefully and frequently evaluated for the presence of bradycardia, heart block, and tachyarrhythmias. Preemptive treatment with permanent pacemakers or implanted defibrillators is appropriate in patients with conduction system disease or who are at risk for ventricular arrhythmias.

Partial deficiency of emerin caused by a splice site mutation in EMD

Emery-Dreifuss muscular dystrophy (EDMD) is caused by mutations in the EMD gene on the X chromosome, which codes for emerin, an inner nuclear membrane protein. Monoclonal antibodies against the N-terminus of emerin protein are used to screen for emerin deficiency in clinical practice. However, these tests may not accurately reflect the disease in some cases. We herein describe the identification of a splice site mutation in the EMD gene in a Japanese patient who suffered from complete atrioventricular conduction block, mild muscle weakness and joint contracture, and a persistently elevated serum creatine kinase level. We used multiple antibodies to confirm the presence of a novel truncating mutation in emerin without the transmembrane region and C-terminus in the skeletal muscle.

[Cardiac sinus node dysfunction due to a new mutation of the SCN5A gene]

A 10-year-old child was hospitalized for bradycardia during a viral infection with chikungunya. His history showed unexplored episodes of bradycardia. Cardiologic explorations revealed cardiac sinus node dysfunction (SD). Mutational screening of the SCN5A gene showed that this case was a compound heterozygote for p.Ala735Val and p.Asp1792Asn missense mutants. Five years later, the child underwent a pacemaker insertion after an electrophysiological study performed during an atrial flutter access.

Isolated sinus node dysfunction in an infant with developmental delay

We present a case of an infant with developmental delay, a structurally normal heart, and prolonged sinus pauses that suffered an unmonitored cardiac arrest while in the hospital. An investigation into the etiology of her sinus pauses did not reveal a definitive cause, and she continued to have pauses up to 15 s in duration. Her history of the cardiac arrest and the duration of the pauses guided the physicians' recommendations and the family's decision to undergo pacemaker implantation prior to discharge from the hospital.