Newborn screening for Duchenne muscular dystrophy in China: follow-up diagnosis and subsequent treatment

Comprehensive analysis of 2097 patients with dystrophinopathy based on a database from 2011 to 2021

BACKGROUND

An increasing number of clinical trials for new therapeutic strategies are underway or being considered for dystrophinopathy. Having detailed data on the natural progression of this condition is crucial for assessing the effectiveness of new drugs. However, there's a lack of data regarding the long-term data on the natural course and how it's managed in China. In this study, we offer a comprehensive overview of clinical and molecular findings, as well as treatment outcomes in the Chinese population.

METHODS

Institutional data on all patients with dystrophinopathy from August 2011 to August 2021 were retrospectively reviewed. The data included geographic distribution, age at diagnosis, molecular findings, and treatment options, such as corticosteroids, cardiac interventions, and clinical outcomes.

RESULTS

In total, 2097 patients with dystrophinopathy, including 1703 cases of Duchenne muscular dystrophy (DMD), 311 cases of Becker muscular dystrophy (BMD), 46 cases of intermediate muscular dystrophy (IMD), and 37 cases categorized as "pending" (individuals with an undetermined phenotype), were registered in the Children's Hospital of Fudan University database for dystrophinopathy from August 2011 to August 2021. The spectrum of identified variants included exonic deletions (66.6%), exonic duplications (10.7%), nonsense variants (10.3%), splice-site variants (4.5%), small deletions (3.5%), small insertions/duplications (1.8%), and missense variants (0.9%). Four deep intronic variants and two inversion variants were identified. Regarding treatment, glucocorticoids were administered to 54.4% of DMD patients and 39.1% of IMD patients. The median age at loss of ambulation was 2.5 years later in DMD patients who received glucocorticoid treatment. Overall, one cardiac medicine at least was prescribed to 7.4% of DMD patients, 8.3% of IMD patients, and 2.6% of BMD patients. Additionally, ventilator support was required by four DMD patients. Eligibility for exon skipping therapy was found in 55.3% of DMD patients, with 12.9%, 10%, and 9.6% of these patients being eligible for skipping exons 51, 53, and 45, respectively.

CONCLUSIONS

This is one of the largest studies to have evaluated the natural history of dystrophinopathy in China, which is particularly conducive to the recruitment of eligible patients for clinical trials and the provision of real-world data to support drug development.

Age-Related Blood Levels of Creatine Kinase-MM in Newborns and Patients with Duchenne Muscular Dystrophy: Considerations for the Development of Newborn Screening Algorithms

Duchenne muscular dystrophy (DMD) is an X-linked progressive disorder and the most common type of muscular dystrophy in children. As newborn screening (NBS) for DMD undergoes evaluation for the Recommended Uniform Screening Panel and is already mandated in multiple states, refining NBS algorithms is of utmost importance. NBS for DMD involves measuring creatine kinase-MM (CK-MM) concentration-a biomarker of muscle damage-in dried blood spots. The current test is FDA-approved for samples obtained less than 72 h after birth. Separate reference ranges are needed for samples collected later than 72 h after birth. In this study, we investigated the relationship between age and CK-MM in presumed healthy newborns to inform NBS algorithm designs. In patients with DMD, CK-MM is persistently elevated in childhood and adolescence, while it may be transiently elevated for other reasons in healthy newborns. CK-MM decrease over time was demonstrated by a population sample of 20,306 presumed healthy newborns tested between 0 and 60 days of life and repeat testing of 53 newborns on two separate days. In the population sample, CK-MM concentration was highest in the second 12 h period of life (median = 318 ng/mL) when only 57.6% of newborns tested below 360 ng/mL, the lowest previously published cutoff. By 72 h of age, median CK-MM concentration was 97 ng/mL, and 96.0% of infants had concentrations below 360 ng/mL. Between 72 h and 60 days, median CK-MM concentration ranged from 32 to 37 ng/mL. Establishing age-related cutoffs is crucial for optimizing the sensitivity and specificity of NBS for DMD.

Creatine Kinase-MM/Proto-oncogene Tyrosine-Protein Kinase Receptor as a Sensitive Indicator for Duchenne Muscular Dystrophy Carriers

Duchenne muscular dystrophy (DMD), a lethal X-linked recessive genetic disease, is characterized by progressive muscle wasting which will lead to premature death by cardiorespiratory complications in their late twenties. And 2.5-19% DMD carriers that also suffer from skeletal muscle damage or dilated cardiomyopathy when diagnosed as soon as possible is meaningful for prenatal diagnosis and advance warning for self-health. The current DMD carrier screening mainly relies on detecting serum creatine kinase activity, covering only 50-70% DMD carriers which will cause many false negatives and require the discovery of highly effective biomarker and simple detection procedure for DMD carriers. In this article, we have compiled a comprehensive summary of all documented biomarkers associated with DMD and categorized them based on their expression patterns. We specifically pinpointed novel DMD biomarkers, previously unreported in DMD carriers, and conducted further investigations to explore their potential. Compared to creatine kinase activity alone in DMD carriers, creatine kinase-MM can improve the specificity from 73 to 81%. And our investigation revealed another promising protein: proto-oncogene tyrosine-protein kinase receptor (RET). When combined with creatine kinase-MM (creatine kinase-MM/RET ratio), it significantly enhances the specificity (from 81 to 83%) and sensitivity (from 71.4 to 93%) of detecting DMD carriers in serum. Moreover, we successfully devised an efficient method for extracting RET from dried blood spots. This breakthrough allowed us to detect both creatine kinase-MM and RET using dried blood spots without compromising the detection rate.

Diagnostic Accuracy of Creatine Kinase Isoenzyme-MM Test in Newborn Screening for Duchenne Muscular Dystrophy: A Systematic Review and Meta-Analysis

BACKGROUND

To systematically evaluate the diagnostic accuracy of the creatine kinase isoenzyme-MM (CK-MM) test in newborn screening for Duchenne muscular dystrophy (DMD).

METHODS

A comprehensive literature search was conducted up to October 31, 2022, in PubMed, Embase, Cochrane Library, Web of Science, and Scopus Database. To evaluate the diagnostic value, the sensitivity (SEN), specificity (SPE), positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), area under the curve (AUC), and Q∗ index were pooled. Threshold effect followed by subgroup analysis and meta-regression were performed to explore the source of heterogeneity. Sensitivity analysis was used to verify the robustness of the findings.

RESULTS

A total seven studies with 248,853 newborns was included in our meta-analysis. The pooled SEN and SPE were 1.00 (95% confidence interval [CI]: 0.89∼1.00) and 1.00 (95% CI: 1.00 to 1.00), respectively; the PLR and NLR were 1004.59 (95% CI: 251.37∼4014.91) and 0.13 (95% CI: 0.05∼0.34), respectively; the DOR was 877.96 (95% CI: 983.24∼78,366.32); the AUC and Q index were 0.8683 and 0.9326, respectively. Sensitivity analysis showed that two studies had an impact on the pooled results and mainly contributed to the heterogeneity.

CONCLUSIONS

CK-MM test demonstrated high accuracy in newborn screening for DMD and may be a valuable alternative in the early diagnosis of the disease followed by confirmatory genetic testing.

Detecting early signs in Duchenne muscular dystrophy: comprehensive review and diagnostic implications

Despite the early onset of clinical signs suggestive of Duchenne muscular dystrophy (DMD), a diagnosis is often not made until four years of age or older, with a diagnostic delay of up to two years from the appearance of the first symptoms. As disease-modifying therapies for DMD become available that are ideally started early before irreversible muscle damage occurs, the importance of avoiding diagnostic delay increases. Shortening the time to a definite diagnosis in DMD allows timely genetic counseling and assessment of carrier status, initiation of multidisciplinary standard care, timely initiation of appropriate treatments, and precise genetic mutation characterization to assess suitability for access to drugs targeted at specific mutations while reducing the emotional and psychological family burden of the disease. This comprehensive literature review describes the early signs of impairment in DMD and highlights the bottlenecks related to the different diagnostic steps. In summary, the evidence suggests that the best mitigation strategy for improving the age at diagnosis is to increase awareness of the early symptoms of DMD and encourage early clinical screening with an inexpensive and sensitive serum creatine kinase test in all boys who present signs of developmental delay and specific motor test abnormality at routine pediatrician visits.

Newborn screening for Duchenne muscular dystrophy: A two-year pilot study

OBJECTIVE

Duchenne muscular dystrophy (DMD) is an X-linked disorder resulting in progressive muscle weakness and atrophy, cardiomyopathy, and in late stages, cardiorespiratory impairment, and death. As treatments for DMD have expanded, a DMD newborn screening (NBS) pilot study was conducted in New York State to evaluate the feasibility and benefit of NBS for DMD and to provide an early pre-symptomatic diagnosis.

METHODS

At participating hospitals, newborns were recruited to the pilot study, and consent was obtained to screen the newborn for DMD. The first-tier screen measured creatine kinase-MM (CK-MM) in dried blood spot specimens submitted for routine NBS. Newborns with elevated CK-MM were referred for genetic counseling and genetic testing. The latter included deletion/duplication analysis and next-generation sequencing (NGS) of the DMD gene followed by NGS for a panel of neuromuscular conditions if no pathogenic variants were detected in the DMD gene.

RESULTS

In the two-year pilot study, 36,781 newborns were screened with CK-MM. Forty-two newborns (25 male and 17 female) were screen positive and referred for genetic testing. Deletions or duplications in the DMD gene were detected in four male infants consistent with DMD or Becker muscular dystrophy. One female DMD carrier was identified.

INTERPRETATION

This study demonstrated that the state NBS program infrastructure and screening technologies we used are feasible to perform NBS for DMD. With an increasing number of treatment options, the clinical utility of early identification for affected newborns and their families lends support for NBS for this severe disease.

Multi-Laboratory Evaluation of Prototype Dried Blood Spot Quality Control Materials for Creatine Kinase-MM Newborn Screening Assays

Pilot studies to detect newborns with Duchenne Muscular Dystrophy (DMD) by newborn bloodspot screening (NBS) have been conducted under the New York State Newborn Screening Program (NYS) and are currently in progress as part of the Early Check Program at Research Triangle Institute (RTI) International. The Newborn Screening Quality Assurance Program (NSQAP) at the U.S. Centers for Disease Control and Prevention (CDC) produced a set of seven prototype dried blood spot (DBS) reference materials spiked with varying levels of creatine kinase MM isoform (CK-MM). These DBS were evaluated over a 3-week period by CDC, NYS, and RTI, all using the same CK-MM isoform-specific fluoroimmunoassay. Results from each laboratory were highly correlated with the relative proportion of CK-MM added to each of the six spiked pools. Based on reference ranges established by NYS and RTI for their pilot studies, these contrived DBS collectively spanned the CK-MM ranges found in typical newborns and the elevated ranges associated with DMD. This set allows quality assessment over the wide range of fluctuating CK-MM levels in typical and DMD-affected newborns.

Newborn Screening for the Diagnosis and Treatment of Duchenne Muscular Dystrophy

A pilot newborn screening (NBS) program for Duchenne muscular dystrophy (DMD) study proposes to assess the feasibility of the screening procedure, temporal course of the various steps of screening, and the public acceptability of the program. This is particularly vital to ascertain as DMD is considered a 'non-treatable' disease and thus does not fit the traditional criteria for newborn screening. However, modern perspectives of NBS for DMD are changing and point to possible net benefits for children and their families undertaking NBS for DMD. The aim of this workshop was to establish pathways for the successful implementation and evaluation of a pilot NBS for DMD program in Australia. Consensus was reached as to the rationale for, potential benefits, risks, barriers and facilitators of screening, alongside the establishment of screening protocols and clinical referral pathways.

Biomarkers in Duchenne Muscular Dystrophy: Current Status and Future Directions

 Duchenne muscular dystrophy is a severe, X-linked disease characterized by decreased muscle mass and function in children. Genetic and biochemical research over the years has led to the characterization of the cause and the pathophysiology of the disease. Moreover, the elucidation of genetic mechanisms underlining Duchenne muscular dystrophy has allowed for the design of innovative personalized therapies.The identification of specific, accurate, and sensitive biomarkers is becoming crucial for evaluating muscle disease progression and response to therapies, disease monitoring, and the acceleration of drug development and related regulatory processes.This review illustrated the up-to-date progress in the development of candidate biomarkers in DMD at the level of proteins, metabolites, micro-RNAs (miRNAs) and genetic modifiers also highlighting the complexity of translating research results to clinical practice.We highlighted the challenges encountered in translating biomarkers into the clinical context and the existing bottlenecks hampering the adoption of biomarkers as surrogate endpoints. These challenges could be overcome by national and international collaborative efforts, multicenter data sharing, definition of public biobanks and patients' registries, and creation of large cohorts of patients. Novel statistical tools/ models suitable to analyze small patient numbers are also required.Finally, collaborations with pharmaceutical companies would greatly benefit biomarker discovery and their translation in clinical trials.

A pilot study of newborn screening for Duchenne muscular dystrophy in Guangzhou

Background

To estimate the overall situation of Duchenne muscular dystrophy (DMD) screening in newborns in Guangzhou, China.

Method

A total of 62553 newborns including 44268 males and 18285 females were screened for DMD by measuring muscle specific creatine kinase isoform (CK-MM) concentrations using the GSP® Neonatal CK-MM kit based on time-resolved immunofluorescence. We recalled positive cases and recollected dried blood spots (DBS) for retest of CK-MM. The newborns with retest positive result were recalled again for serum creatine kinase (CK) and multiplex ligation-dependent probe amplification (MLPA) test. Whole exon sequencing was performed when MLPA test was negative.

Results

Four males were diagnosed with DMD. The incidence of males was 1/11067. No DMD patient was found in female. There were significant differences of CK-MM concentration between male and female newborns. Among gestational age (GA), birth weight (BW) and age at sampling, linear regression analysis showed that CK-MM concentration was much more closely correlated with GA and age at sampling.

Conclusions

CK-MM concentration is affected by gender, GA, BW and age at sampling. The efficiency of DMD screening might be improved by adjusting a multitier cut-off value according to GA and age at sampling. DMD newborn screening should be male priority.

•

A total of 62553 newborns including 44268 males and 18285 females were screened for DMD in Guangzhou.

•

Four males were diagnosed with DMD. The incidence of males was 1/11067. No DMD patient found in female.

•

DMD newborn screening should be male priority.

•

The efficiency of DMD screening might be improved by adjusting a multitier cut-off value according to GA and age at sampling.

Electrocardiographic features of children with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a clinically common X-linked recessive myopathy, which is caused by mutation of the gene encoding dystrophin on chromosome Xp21. The onset of heart injury in children with DMD is inconspicuous, and the prognosis is poor once it develops to the stage of heart failure. Cardiovascular complications remain an important cause of death in this patient population. At present, population and animal studies have suggested that Electrocardiogram (ECG) changes may be the initial manifestation of cardiac involvement in children with DMD. Relevant clinical studies have also confirmed that significant abnormal ECG changes already exist in DMD patients before cardiomegaly and/or LVEF decrease. With increases in age and decreases in cardiac function, the proportion of ECG abnormalities in DMD patients increase significantly. Some characteristic ECG changes, such as ST-segment changes, T wave inversion, Q wave at the inferolateral leads, LBBB and SDANN, have a certain correlation with the indexes of cardiac remodeling or impaired cardiac function in DMD patients, while VT and LBBB have demonstrated relatively good predictive value for the occurrence of long-term DCM and/or adverse cardiovascular events or even death in DMD patients. The present review discusses the electrocardiographic features in children with DMD.

Creatine kinase-MM concentration in dried blood spots from newborns and implications for newborn screening for Duchenne muscular dystrophy

Introduction/Aims

Creatine kinase‐MM (CK‐MM) is a marker of skeletal muscle damage. Detection of elevated levels of CK‐MM in newborns can enable an early suspicion of the diagnosis of Duchenne muscular dystrophy (DMD) before symptom onset. Our aim was to investigate CK‐MM levels in DMD‐affected and unaffected newborns using an immunoassay that measures CK‐MM concentration in dried blood spots collected for routine newborn screening.

Methods

To validate the assay in our laboratory, CK‐MM measurements and newborn demographic information were collected for 8584 de‐identified specimens and 15 confirmed DMD patients. After analyzing validation data, CK‐MM normal ranges were determined based on age of newborn at specimen collection. Subsequently, the assay was used to measure CK‐MM concentration in 26 135 newborns as part of a consented pilot study to screen for DMD in New York State. Mean and median levels of CK‐MM based on age of collection, in addition to the 2.5th, 50th, 97.5th, and 99.5th percentiles, were recalculated using the validation and screening data sets.

Results

Median CK‐MM within 1 hour of birth was 109 ng/mL, rose to a high of 499 ng/mL at 25 hours of age, and then declined to 200 ng/mL at 2 days of life. The median continued to decline more slowly and then stabilized at approximately 40 ng/mL at 1 week of life.

Discussion

Because of the marked variability and elevated CK‐MM levels observed within the first days of life, it is important to set multiple CK‐MM age‐related cut‐offs when screening for DMD in newborns.

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.

Application of a next-generation sequencing (NGS) panel in newborn screening efficiently identifies inborn disorders of neonates

Background

Newborn screening (NBS) has been implemented for neonatal inborn disorders using various technology platforms, but false-positive and false-negative results are still common. In addition, target diseases of NBS are limited by suitable biomarkers. Here we sought to assess the feasibility of further improving the screening using next-generation sequencing technology.

Methods

We designed a newborn genetic sequencing (NBGS) panel based on multiplex PCR and next generation sequencing to analyze 134 genes of 74 inborn disorders, that were validated in 287 samples with previously known mutations. A retrospective cohort of 4986 newborns was analyzed and compared with the biochemical results to evaluate the performance of this panel.

Results

The accuracy of the panel was 99.65% with all samples, and 154 mutations from 287 samples were 100% detected. In 4986 newborns, a total of 113 newborns were detected with biallelic or hemizygous mutations, of which 36 newborns were positive for the same disorder by both NBGS and conventional NBS (C-NBS) and 77 individuals were NBGS positive/C-NBS negative. Importantly, 4 of the 77 newborns were diagnosed currently including 1 newborn with methylmalonic acidemia, 1 newborn with primary systemic carnitine deficiency and 2 newborns with Wilson’s disease. A total of 1326 newborns were found to be carriers with an overall carrier rate of 26.6%.

Conclusion

Analysis based on next generation sequencing could effectively identify neonates affected with more congenital disorders. Combined with C-NBS, this approach may improve the early and accurate identification of neonates with inborn disorders. Our study lays the foundation for prospective studies and for implementing NGS-based analysis in NBS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02231-x.

Evaluation of the GSP Creatine Kinase-MM Assay and Assessment of CK-MM Stability in Newborn, Patient, and Contrived Dried Blood Spots for Newborn Screening for Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a fatal X-linked disorder with a birth prevalence of 19.8:100,000 males worldwide. Elevated concentration of the muscle enzyme creatine kinase-MM (CK-MM) allows for presymptomatic screening of newborns using Dried Blood Spots (DBS). We evaluated imprecision and carryover of the FDA-approved PerkinElmer GSP Neonatal CK-MM kit over multiple runs, days, and operators, followed by quantification of CK-MM loss in stored newborn, contrived, and non-newborn patient DBS resulting from exposure to ambient versus low humidity (50-day trial), and high humidity and high temperature (8-day trial). Imprecision %CV was ≤14% for all verification comparisons and over 6 months of testing. On average, the mean CK-MM recovery after 50 days was >80% of initial concentration for all sample types stored in low humidity and <80% in ambient humidity. After 8 days of storage in high humidity and high temperature, the mean recovery for newborn samples was <80%. Verification results for the GSP Neonatal CK-MM assay were concordant with kit parameters and the assay performed consistently over 6 months. CK-MM degradation in ambient storage can be mitigated by reducing exposure to humidity. Assessment of DBS shipping and storage conditions is recommended prior to implementing DMD screening.

Current diagnosis and management of rare pediatric diseases in China

This review categorizes and summarizes the rare pediatric diseases that have been included in the First List of Rare Diseases that was jointly published by the National Health Commission and four other government departments in China in 2018. In total, 58 diseases that develop during childhood are included. These diseases involve nine organ systems, including the musculoskeletal, respiratory, immune, endocrine and metabolic, nervous, cardiovascular, hematological, urinary, and integumentary systems. Affected children often have multiorgan involvement with various presentations. Severe diseases can cause acute symptoms starting in the neonatal period that lead to increased morbidity and mortality without prompt management. Early diagnosis and treatment can significantly change the course of a disease and improve its prognosis. This work systemically reviews the status of rare pediatric diseases with a relatively high incidence in the First List of Rare Diseases.

Newborn screening of neuromuscular diseases

Neuromuscular diseases represent an heterogenous group of more than 400 diseases, with a very broad phenotypic spectrum. Given their rarity and complexity, neuromuscular diseases are often diagnosed with a very significant delay after which irreversible muscle damage may limit the efficacy of treatments when available. In this context, neonatal screening could constitute a solution for early detection and treatment. A systematic review of the literature in PubMed up to May 1, 2021, was conducted according to PRISMA guidelines, including classical neuromuscular diseases and diseases with a clear peripheral nervous system involvement (including central nervous system disease with severe neuropathy). We found seven diseases for which newborn screening data were reported: spinal muscular atrophy (9), Duchenne muscular dystrophy (9), Pompe disease (8), X-linked adrenoleukodystrophy (5), Krabbe disease (4), myotonic dystrophy type 1 (1), metachromatic leukodystrophy (1). The future of newborn screening for neuromuscular disorders pass through a global technological switch, from a biochemical to a genetic-based approach. The rapid development of therapy also requires the possibility to quickly adapt the list of treated conditions, to allow innovative therapies to achieve their best efficacy.

Comparison of Carrier and de novo Pathogenic Variants in a Chinese DMD/BMD Cohort

Background: Duchenne and Becker muscular dystrophy (DMD/BMD) are X-linked recessively inherited neuromuscular disorders caused by deletions, duplications, or small mutations in the DMD gene. With advances in prenatal diagnosis decreasing the number of affected offspring from carrier mothers, the frequency of de novo variants could increase. Therefore, determining the differences between the carrier and de novo variants of the DMD gene, which are rarely explored, is important for trial planning and genetic diagnosis in the future.

Methods: A total of 440 patients, 349 of whom had DMD and 91 had BMD, diagnosed in our department between 2012 and 2019, along with their respective mothers, were included in this study. Multiplex ligation-dependent probe amplification was used to detected deletions and duplications in patients and their mothers. Small mutations were detected using next-generation sequencing in the patients, followed by Sanger sequencing in the mothers.

Results: Deletions, duplications, and small mutations were identified in 204, 46, and 99 of the 349 patients with DMD and in 50, 10, and 31 of the 91 patients with BMD, respectively. De novo deletions were more concentrated in hotspot regions than carrier deletions of DMD/BMD. No clear bias was observed in the variant distribution between carriers, de novo duplications, and small mutations in DMD/BMD. The carrier frequency of DMD (61.6%) was lower than that of BMD (69.2%), but the difference was not statistically significant. The carrier frequency of deletions of the DMD gene (51.2%) was significantly lower than those of duplications (75%) and small mutations (81.5%).

Conclusion: Compared to de novo deletions, deletions from carrier mothers had a wider distribution. Moreover, there was no significant difference between the carrier frequencies of DMD and BMD. Duplications and small mutations were more commonly inherited, while deletions were present de novo.

Genotype characterization and delayed loss of ambulation by glucocorticoids in a large cohort of patients with Duchenne muscular dystrophy

Background

Duchenne muscular dystrophy (DMD) is the most common genetic muscle disease in human. We aimed to describe the genotype distribution in a large cohort of Chinese DMD patients and their delayed loss of ambulation by glucocorticoid (GC) treatments. This is to facilitate protocol designs and outcome measures for the emerging DMD clinical trials.

Results

A total of 1163 patients with DMD were recruited and genotyped. Genotype variations were categorized as large deletions, large duplications, and small mutations. Large deletions were further analyzed for those amenable to exon-skipping therapies. Participants aged 5 years or older were grouped into GC-treated and GC-naïve groups. Clinical progression among different genotypes and their responses to GC treatments were measured by age at loss of ambulation (LOA). Among the mutation genotypes, large deletions, large duplications, and small mutations accounted for 68.79%, 7.14%, and 24.07%, respectively. The mean age at diagnosis was 4.59 years; the median ages at LOA for the GC-naïve, prednisone/prednisolone-treated, and deflazacort-treated groups were 10.23, 12.02, and 13.95 years, respectively. The “deletion amenable to skipping exon 44” subgroup and the nonsense-mutation subgroup had older ages at LOA than the “other deletions” subgroup. Subgroups were further analyzed by both genotypes and GC status. All genotypes showed significant beneficial responses to GC treatment. Deletions amenable to skipping exon 44 showed a lower hazard ratio (0.155). The mean age at death was 18.57 years in this DMD group.

Conclusion

Genotype variation influences clinical progression in certain DMD groups. Beneficial responses to GC treatment were observed among all DMD genotypes. Compared with other genotypes, deletions amenable to skipping exon 44 had a lower hazard ratio, which may indicate a stronger protective effect of GC treatments on this subgroup. These data are valuable for designing future clinical trials, as clinical outcomes may be influenced by the genotypes.

A Comprehensive Analysis of 2013 Dystrophinopathies in China: A Report From National Rare Disease Center

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are X-linked recessive neuromuscular disorders caused by mutations in DMD. A high-quality database of DMD/BMD is essential not only for clinical practice but also for fundamental research. Here, we aimed to build the largest Chinese national dystrophinopathy database using the National Rare Diseases Registry System of China. Peking Union Medical College Hospital (PUMCH) was the National Rare Diseases Center of China. This research involved 2013 patients with dystrophinopathies, whose diagnoses were confirmed; they were registered and followed up at PUMCH from March 2011 to December 2018. Family history, clinical signs, and treatment data were reported for patients with DMD and BMD at different rates. All six serum biochemical indexes could accurately distinguish between DMD and BMD patients. Copy number variations were the most frequent mutation type (79.2% in DMD and 84.3% in BMD), of which large deletions accounted for 88.4 and 88.6%, large duplications accounted for 11.6 and 11.4% in DMD and BMD, respectively. An exon deletion hotspot, located in exons 45-54, was observed in DMD, and intron 44 was the most frequent deletion starting point (26.5%). Duplication and single nucleotide variations appeared to be uniformly distributed among all exons. Eleven patients were identified to have ultrarare mutation types. Eleven other patients suffered from two separate mutations simultaneously, some of which may have taken place via dependent mechanisms. Thus, we have established the largest hospital-based Chinese dystrophinopathy database via the National Rare Diseases Registry System. This study provides valuable information for further diagnostic and therapeutic studies of dystrophinopathy.

Population-Wide Duchenne Muscular Dystrophy Carrier Detection by CK and Molecular Testing

Carrier screening of Duchenne muscular dystrophy (DMD) has not been widely evaluated. To identify definite DMD female carriers prior to or in early pregnancy, we studied a large population of reproductive age females and provided informed reproductive options to DMD carriers. 37268 females were recruited from the Hangzhou Family Planning Publicity and Technology Guidance Station/Hangzhou Health Service Center for Children and Women, Hangzhou, China, between October 10, 2017, and December 16, 2018. CK activity was measured with follow-up serum DMD genetic testing in subjects with hyperCKemia, defined as CK > 200 U/L. The calculated upper reference limit (97.5^th percentile) of serum creatine kinase (CK) for females aged 20-50 years in this study was near the reference limit recommended by the manufacturer (200 U/L), above which was defined as hyperCKemia. 427 females (1.2%) harbored initially elevated CK, among which 281 females (response rate of 65.8%) accepted CK retesting. DMD genetic testing was conducted on 62 subjects with sustained serum CK > 200 U/L and 16 females with a family history of DMD. Finally, 6 subjects were confirmed to be DMD definite carriers. The estimated DMD female carrier rate in this study was 1 : 4088 (adjusting for response rate), an underestimated rate, since only 50% to 70% of DMD female carriers manifest elevated serum CK, and carriers in this study may have been missed due to lack of follow-up or inability to detect all DMD pathogenic variants by current genetic testing.

Is it the right time for an infant screening for Duchenne muscular dystrophy?

Newborn screening (NBS) is an essential, preventive public health programme for early identification of disorders whose early treatment can lead to significant reduction in morbidity and mortality. NBS for Duchenne muscular dystrophy (DMD) has been a controversial matter for many years, because of false positives, the lack of effective drugs and the need of more data about screening efficacy. The still high diagnostic delay of DMD and the current availability of drugs such as steroid, ataluren, eteplirsen, golodirsen and forthcoming new drugs, improving the clinical conditions if early started, make appropriate to begin a concrete discussion between stakeholders to identify best practice for DMD screening. A two-step system CK/DNA screening programme is presented to be performed in male infants aged between 6 months and 42 months involving more than 30,000 male infants. Five to eight DMD subjects are believed to be diagnosed. The pilot project would give the opportunity to test in a small population the feasibility of an infant screening programme, which in the near future could be applicable to an entire country.

Progress in treatment and newborn screening for Duchenne muscular dystrophy and spinal muscular atrophy

BACKGROUND

Advances in treatment for Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA) hold promise for children with these disorders. Accurate genetic diagnosis, early in the disease process, will allow these treatments to be most effective. Newborn screening (NBS) for SMA has been recommended in the United States, and a pilot DMD NBS program is underway in Hangzhou, China.

DATA SOURCES

A PubMed search, limited to the past 5 years, was conducted to identify: (1) therapeutic advancements for DMD/SMA approved by the United States Food and Drug Administration or the European Medicine Agency and (2) The status of NBS for DMD/SMA.

RESULTS

We review the current state of approved treatments for DMD/SMA. We present recommendations regarding the future of NBS for these diseases, with a focus on the outcomes and challenges of SMA NBS in New York, USA, and the DMD NBS pilot program in Hangzhou, China.

CONCLUSIONS

Approved treatments for DMD and SMA may change the natural history of these diseases. Long-term studies of these treatments are underway. To avoid the known diagnostic delay associated with these disorders and provide optimal effectiveness of these treatments, early identification of patients through NBS will be necessary. Establishing comprehensive follow-up plans for positively identified patients will need to be in place for NBS programs to be successful.