Screening for Duchenne muscular dystrophy in Germany, 1977-2011: A personal story

Early diagnosis of Duchenne muscular dystrophy - A Treat-NMD international workshop

The diagnosis of Duchenne muscular dystrophy (DMD) is significant at any stage, however an early diagnosis in a presymptomatic or very early phase of DMD, offers unique opportunities and challenges for families and health care providers. Currently, there is limited evidence as to the optimal models of care during this stage of the condition.. To address this, in 2023, Treat-NMD facilitated the Early Diagnosis for DMD project; bringing together 42 experts from across Europe, the US and Australasia, including health care professionals, researchers, and people with lived experience to discuss the complexities of an early or newborn diagnosis of DMD, and provide recommendations regarding approaches to multidisciplinary care. A series of virtual meetings followed by a hybrid workshop resulted in broad recommendations to support clinicians in caring for children and families following an early diagnosis of DMD. The workshop did not define a cut-off for early diagnosis, however much of the discussion focused on diagnoses that occurred prior to 2 years. There is recognition that boys may first present with non-motor symptoms, such as speech delay or neurodevelopmental issues that are secondary to their dystrophinopathy, and therefore this report refers reflects that infants with DMD may be presymptomatic or early symptomatic.

A new pseudoexon activation due to ultrarare branch point formation in Duchenne muscular dystrophy

Deep-intronic variants that create or enhance a splice site are increasingly reported as a significant cause of monogenic diseases. However, deep-intronic variants that activate pseudoexons by affecting a branch point are extremely rare in monogenic diseases. Here, we describe a novel deep-intronic DMD variant that created a branch point in a Duchenne muscular dystrophy (DMD) patient. A 7.0-year-old boy was enrolled because he was suspected of DMD based on his clinical, muscle imaging, and pathological features. Routine genetic testing did not discover a pathogenic DMD variant. We then performed muscle-derived dystrophin mRNA analysis and detected an aberrant pseudoexon-containing transcript. Further genomic Sanger sequencing and bioinformatic analyses revealed a novel deep-intronic splicing variant in DMD (NM_004006.2:c.5325+1759G>T), which created a new branch point sequence and thus activated a new dystrophin pseudoexon (NM_004006.2:r.5325_5326ins5325+1779_5325+1855). Our study highlights the significant role of branch point alterations in the pathogenesis of monogenic diseases.

Duchenne muscular dystrophy

Duchenne muscular dystrophy is a severe, progressive, muscle-wasting disease that leads to difficulties with movement and, eventually, to the need for assisted ventilation and premature death. The disease is caused by mutations in DMD (encoding dystrophin) that abolish the production of dystrophin in muscle. Muscles without dystrophin are more sensitive to damage, resulting in progressive loss of muscle tissue and function, in addition to cardiomyopathy. Recent studies have greatly deepened our understanding of the primary and secondary pathogenetic mechanisms. Guidelines for the multidisciplinary care for Duchenne muscular dystrophy that address obtaining a genetic diagnosis and managing the various aspects of the disease have been established. In addition, a number of therapies that aim to restore the missing dystrophin protein or address secondary pathology have received regulatory approval and many others are in clinical development.

Newborn screening of duchenne muscular dystrophy specifically targeting deletions amenable to exon-skipping therapy

Duchenne Muscular Dystrophy (DMD) is a lethal progressive muscle-wasting disease. New treatment strategies relying on DMD gene exon-skipping therapy have recently been approved and about 30% of patients could be amenable to exon 51, 53 or 45 skipping. We evaluated the spectrum of deletions reported in DMD registries, and designed a method to screen newborns and identify DMD deletions amenable to exon 51, 53 and 45 skipping. We developed a multiplex qPCR assay identifying hemi(homo)-zygotic deletions of the flanking exons of these therapeutic targets in DMD exons (i.e. exons 44, 46, 50, 52 and 54). We conducted an evaluation of our new method in 51 male patients with a DMD phenotype, 50 female carriers of a DMD deletion and 19 controls. Studies were performed on dried blood spots with patient's consent. We analyzed qPCR amplification curves of controls, carriers, and DMD patients to discern the presence or the absence of the target exons. Analysis of the exons flanking the exon-skipping targets permitted the identification of patients that could benefit from exon-skipping. All samples were correctly genotyped, with either presence or absence of amplification of the target exon. This proof-of-concept study demonstrates that this new assay is a highly sensitive method to identify DMD patients carrying deletions that are rescuable by exon-skipping treatment. The method is easily scalable to population-based screening. This targeted screening approach could address the new management paradigm in DMD, and could help to optimize the beneficial therapeutic effect of DMD therapies by permitting pre-symptomatic care.

Significance of Asymptomatic Hyper Creatine-Kinase Emia

OBJECTIVES

Whether asymptomatic hyper-CKemia (AHCE) should prompt a thorough work-up for muscle disease or not is controversially discussed. This review aims at summarizing and discussing recent findings concerning the cause, frequency, evolution, and work-up of conditions manifesting as AHCE and normal or abnormal electromyography (EMG) respectively muscle biopsy.

METHODS

Systematic PubMed search.

RESULTS

There are numerous primary (hereditary) and acquired myopathies that manifest with permanent, recurrent, or temporary AHCE with/without myopathic EMG or muscle biopsy. AHCE particularly occurs at onset of these conditions, which include dystrophinopathies, myotilinopathies, calpainopathy, caveolinopathy, dysferlinopathy, central core disease, multicore disease, desminopathy, MD1, MD2, hypoPP, malignant hyperthermia susceptibility, Pompe disease, McArdle disease, myoadenylate deaminase-deficiency, CPT2-deficiency, mitochondrial disorders, or myopathy with tubular aggregates. Most likely, other primary myopathies manifest with AHCE as well, without having been reported. Patients with AHCE should be taken seriously and repeated CK determination must be conducted. If hyper-CKemia is persisting or recurrent, these patients should undergo an EMG and eventually muscle biopsy. If noninformative, genetic work-up by a panel or whole exome sequencing should be initiated, irrespective of the family history. Patients with AHCE should avoid excessive exercise, require sufficient hydration, require counseling with regard to the risk of malignant hyperthermia, and should inform anesthesiologists and surgeons about their condition before elective surgery.

CONCLUSIONS

Recurrent AHCE should be taken seriously and managed with conventional work-up. If noninformative, genetic work-up should follow irrespective of the family history.