Ethnicity-related DMD Genotype Landscapes in European and Non-European Countries

Objective

Genetic diagnosis and mutation identification are now compulsory for Duchenne (DMD) and Becker muscular dystrophies (BMD), which are due to dystrophin (DMD) gene mutations, either for disease prevention or personalized therapies. To evaluate the ethnic-related genetic assortments of DMD mutations, which may impact on DMD genetic diagnosis pipelines, we studied 328 patients with DMD and BMD from non-European countries.

Methods

We performed a full DMD mutation detection in 328 patients from 10 Eastern European countries (Poland, Hungary, Lithuania, Romania, Serbia, Croatia, Bosnia, Bulgaria, Ukraine, and Russia) and 2 non-European countries (Cyprus and Algeria). We used both conventional methods (multiplex ligation-dependent probe amplification [MLPA] followed by gene-specific sequencing) and whole-exome sequencing (WES) as a pivotal study ran in 28 patients where DMD mutations were already identified by standard techniques. WES output was also interrogated for DMD gene modifiers.

Results

We identified DMD gene mutations in 222 male patients. We identified a remarkable allele heterogeneity among different populations with a mutation landscape often country specific. We also showed that WES is effective for picking up all DMD deletions and small mutations and its adoption could allow a detection rate close to 90% of all occurring mutations. Gene modifiers haplotypes were identified with some ethnic-specific configurations.

Conclusions

Our data provide unreported mutation landscapes in different countries, suggesting that ethnicity may orient genetic diagnosis flowchart, which can be adjusted depending on the mutation type frequency, with impact in drug eligibility.

Acute Myocardial Injury in a Child with Duchenne Muscular Dystrophy: Pulse Steroid Therapy?

Heart implication in Duchenne muscular dystrophy usually is present in the form of dilated cardiomyopathy, manifested as heart failure and arrhythmias. To delay progression, including heart deterioration, prednisone is recommended as preventive treatment. We report the case of an 11-year-old boy diagnosed with Duchenne muscular dystrophy at the age of seven, who was on preventive treatment with oral prednisone (0.75 mg/kg/day) and beta blocker (metoprolol, 1 mg/kg/day). Suddenly, the patient presented acute chest pain, vomiting and sweating. The electrocardiogram showed ST elevation in inferior leads. Troponin T was increased to 30814 pg/ml (normal values <14 pg/mL). The echocardiography revealed reduced contractility of the posteroinferior wall of the left ventricle. After excluding coronary implications by coronary angiography, we increased the oral prednisone to 1.4 mg/kg/day for five days and added enalapril (0.5 mg/kg/day, po). The response was positive, with a rapid decrease of the troponin T value to 3186 pg/mL in five days and gradual recovery of myocardial contractility afterwards.

Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea

The neuromuscular junction (NMJ) is one of the best-studied cholinergic synapses. Inherited defects of peripheral neurotransmission result in congenital myasthenic syndromes (CMSs), a clinically and genetically heterogeneous group of rare diseases with fluctuating fatigable muscle weakness as the clinical hallmark. Whole-exome sequencing and Sanger sequencing in six unrelated families identified compound heterozygous and homozygous mutations in SLC5A7 encoding the presynaptic sodium-dependent high-affinity choline transporter 1 (CHT), which is known to be mutated in one dominant form of distal motor neuronopathy (DHMN7A). We identified 11 recessive mutations in SLC5A7 that were associated with a spectrum of severe muscle weakness ranging from a lethal antenatal form of arthrogryposis and severe hypotonia to a neonatal form of CMS with episodic apnea and a favorable prognosis when well managed at the clinical level. As expected given the critical role of CHT for multisystemic cholinergic neurotransmission, autonomic dysfunctions were reported in the antenatal form and cognitive impairment was noticed in half of the persons with the neonatal form. The missense mutations induced a near complete loss of function of CHT activity in cell models. At the human NMJ, a delay in synaptic maturation and an altered maintenance were observed in the antenatal and neonatal forms, respectively. Increased synaptic expression of butyrylcholinesterase was also observed, exposing the dysfunction of cholinergic metabolism when CHT is deficient in vivo. This work broadens the clinical spectrum of human diseases resulting from reduced CHT activity and highlights the complexity of cholinergic metabolism at the synapse.

Intellectual disability and epilepsy in down syndrome

Down Syndrome (DS) is the most common genetic cause of mental retardation, with a reported frequency of epilepsy between 1.4-17% (1). There is a paucity of data in the literature regarding epilepsy in Down syndrome and its relation to intellectual disability.

OBJECTIVES

The purpose of this article is to analyze the association of epilepsy in children with DS - frequency and type of seizures, treatment, outcome and to compare cognitive impairment of children with DS and epilepsy and DS without epilepsy from our cohort.

METHODS

A four years systematic retrospective analysis of the database of the Pediatric Neurology Clinic (January 2010 - December 2013) identified a cohort of 39 pediatric cases with DS and neurological symptoms, 9 of them (23%) associating epileptic seizures. Following data were analysed: clinical and neurological examination, type/s of seizures, electroencephalography (EEG), cerebral magnetic resonance imaging (MRI), psychological examination, psychiatric evaluation in selected cases, electrocardiography (ECG), cardiac ultrasonography, ophthalmologic examination.

RESULTS

23% (9 patients) of the children with DS of our cohort presented epilepsy. Five patients had epileptic spasms (56%), one of these further developed astatic seizures. Focal seizures were observed in three patients (33%) and absence with eyelid myoclonias in one patient (11%). Two of the nine patients with DS and epilepsy had generalized seizures, both with very good response to levetiracetam (LEV). EEG was abnormal at seizure onset, and was improved after treatment. Of the nine children with DS and epilepsy, two (22%) presented mild mental retardation and seven (78%) had moderate to severe cognitive delay. Of the 30 children with DS and without epilepsy, 21 (70%) had mild mental retardation and 9 (30%) had moderate to severe cognitive impairment.

CONCLUSIONS

The most frequent epileptic syndrome associated with DS is West syndrome, with good response to specific antiepileptics. All children with DS from our cohort have intelectual disability, more severe in those with epilepsy. Slight improvement of intelectual and language capabilities were seen after seizures control.

Mapping the differences in care for 5,000 spinal muscular atrophy patients, a survey of 24 national registries in North America, Australasia and Europe

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder characterised by the degeneration of motor neurons and progressive muscle weakness. It is caused by homozygous deletions in the survival motor neuron gene on chromosome 5. SMA shows a wide range of clinical severity, with SMA type I patients often dying before 2 years of age, whereas type III patients experience less severe clinical manifestations and can have a normal life span. Here, we describe the design, setup and utilisation of the TREAT-NMD national SMA patient registries characterised by a small, but fully standardised set of registry items and by genetic confirmation in all patients. We analyse a selection of clinical items from the SMA registries in order to provide a snapshot of the clinical data stratified by SMA subtype, and compare these results with published recommendations on standards of care. Our study included 5,068 SMA patients in 25 countries. A total of 615 patients were ventilated, either invasively (178) or non-invasively (437), 439 received tube feeding and 455 had had scoliosis surgery. Some of these interventions were not available to patients in all countries, but differences were also noted among high-income countries with comparable wealth and health care systems. This study provides the basis for further research, such as quality of life in ventilated SMA patients, and will inform clinical trial planning.

The TREAT-NMD Duchenne muscular dystrophy registries: conception, design, and utilization by industry and academia

Duchenne muscular dystrophy (DMD) is an X-linked genetic disease, caused by the absence of the dystrophin protein. Although many novel therapies are under development for DMD, there is currently no cure and affected individuals are often confined to a wheelchair by their teens and die in their twenties/thirties. DMD is a rare disease (prevalence <5/10,000). Even the largest countries do not have enough affected patients to rigorously assess novel therapies, unravel genetic complexities, and determine patient outcomes. TREAT-NMD is a worldwide network for neuromuscular diseases that provides an infrastructure to support the delivery of promising new therapies for patients. The harmonized implementation of national and ultimately global patient registries has been central to the success of TREAT-NMD. For the DMD registries within TREAT-NMD, individual countries have chosen to collect patient information in the form of standardized patient registries to increase the overall patient population on which clinical outcomes and new technologies can be assessed. The registries comprise more than 13,500 patients from 31 different countries. Here, we describe how the TREAT-NMD national patient registries for DMD were established. We look at their continued growth and assess how successful they have been at fostering collaboration between academia, patient organizations, and industry.

Preliminary results in a study regarding the relationship between perlecan gene polymorphism and spinal muscular atrophy type I disease

Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by weakness and atrophy of proximal muscles. Despite the fact that the disease transmission suggests an autosomal recessive trait, the wide spectrum of clinical manifestations indicates that other genes may contribute to the SMA phenotype. To identify possible modifier genes, the aim of our study was to investigate the relationship between BamH1 perlecan gene polymorphism and SMA type I, the classical severe form of the disease. We genotyped 40 patients with SMA type I disease and 50 subjects without personal or heredo-colateral neuromuscular problems, using the polymerase chain reaction-restriction fragment length polymorphism method. After statistical analysis of the observed genotypes, a significant difference (p = 0.03) could be observed regarding the incidence of TT genotype and T allele in boys with SMA type I compared with affected girls. However, this result cannot be assessed because of the small and unequal number of subjects. We concluded that there might be no association between perlecan gene polymorphism and SMA type I disease.