Newborn screening of neuromuscular diseases

Systematic Review of Newborn Screening Programmes for Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic neuromuscular disorder causing the degeneration of motor neurons in the spinal cord. Recent studies suggest greater effectiveness of treatment in the presymptomatic stage. This systematic review synthesises findings from 37 studies (and 3 overviews) of newborn screening for SMA published up to November 2023 across 17 countries to understand the methodologies used; test accuracy performance; and timing, logistics and feasibility of screening. All studies screened for the homozygous deletion of SMN1 exon 7. Most (28 studies) used RT-PCR as the initial test on dried blood spots (DBSs), while nine studies also reported second-tier tests on DBSs for screen-positive cases. Babies testing positive on DBSs were referred for confirmatory testing via a range of methods. Observed SMA birth prevalence ranged from 1 in 4000 to 1 in 20,000. Most studies reported no false-negative or false-positive cases (therefore had a sensitivity and specificity of 100%). Five studies reported either one or two false-negative cases each (total of six cases; three compound heterozygotes and three due to system errors), although some false-negatives may have been missed due to lack of follow-up of negative results. Eleven studies reported false-positive cases, some being heterozygous carriers or potentially related to heparin use. Time to testing and treatment varied between studies. In conclusion, several countries have implemented newborn screening for SMA in the last 5 years using a variety of methods. Implementation considerations include processes for timely initial and confirmatory testing, partnerships between screening and neuromuscular centres, and timely treatment initiation.

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

The Importance of Early Treatment of Inherited Neuromuscular Conditions

There has been tremendous progress in treatment of neuromuscular diseases over the last 20 years, which has transformed the natural history of these severely debilitating conditions. Although the factors that determine the response to therapy are many and in some instance remain to be fully elucidated, early treatment clearly has a major impact on patient outcomes across a number of inherited neuromuscular conditions. To improve patient care and outcomes, clinicians should be aware of neuromuscular conditions that require prompt treatment initiation. This review describes data that underscore the importance of early treatment of children with inherited neuromuscular conditions with an emphasis on data resulting from newborn screening efforts.

Molecular genetic screening of full-term small for gestational age

OBJECTIVE

To examine the clinical application of genomic screening in newborns small for gestational age (SGA), hoping to provide an efficient technique for early discovery of neonatal diseases, which is necessary to elevate survival rates and the quality of life in infants.

METHODS

Totally 93 full-term SGA newborns were assessed. Dried blood spot (DBS) samples were obtained at 72 h after birth, and tandem mass spectrometry (TMS) and Angel Care genomic screening (GS, using Targeted next generation sequencing) were carried out.

RESULTS

All 93 subjects were examined by Angel Care GS and TMS. No children showing inborn errors of metabolism (IEM) were detected by TMS, while 2 pediatric cases (2.15%, 2/93) were confirmed as thyroid dyshormonogenesis 6 (TDH6) by Angel Care GS. Additionally, 45 pediatric cases (48.4%) had one or more variants conferring a carrier status for recessive childhood-onset disorders, with 31 genes and 42 variants associated with 26 diseases. The top three gene-related diseases with carrier status were autosomal recessive deafness (DFNB), abnormal thyroid hormone and Krabbe disease.

CONCLUSIONS

SGA is tightly associated with genetic variation. Molecular Genetic Screening allows early detection of congenital hypothyroidism and may be a potent genomic sequencing technique for screening newborns.

Room to improve: The diagnostic journey of Spinal Muscular Atrophy

AIMS

To highlight the current diagnostic pathway for children with Spinal Muscular Atrophy (SMA) in Ireland. We look to identify points along the diagnostic pathway that may impede a timely diagnosis, and argue that newborn screening for SMA is the single best measure to remediate these delays.

METHODS

Through retrospective chart review and an online questionnaire, we gathered SMA patient data outlining clinical characteristics and the route to diagnosis of the SMA cohort attending the National SMA Treatment centre at Children's Health Ireland.

RESULTS

We found that 32 children were diagnosed with SMA in Ireland in the 15-years from 2007 to 2021, with twelve cases of SMA type I. Muscle weakness is the most commonly reported initial sign, and the GP is usually the first health provider to address parental concerns. Patients commonly experience delays in diagnosis due to factors such as varied SMA clinical phenotypes, and a lack of experience or awareness of SMA amongst community based health care practitioners. In spite of this, when patients do gain early access to tertiary diagnostics through prenatal or neonatal genetic testing, they then report rapid diagnosis and initiation of disease modifying therapy in the crucial pre-symptomatic window.

CONCLUSION

We conclude that delays to diagnosis inherent within the current Irish system are pervasive and arise prior to engagement with tertiary services. All of these delays are remediable through the establishment of a dedicated SMA newborn screening programme.

Improving Recognition of Treatable Rare Neuromuscular Disorders in Primary Care: A Pilot Feasibility Study

Innovative targeted treatments for neuromuscular disorders (NMDs) can dramatically improve the course of illness. Diagnostic delay, however, is a major impediment. Here, we present a pilot project aimed at assessing the feasibility of a screening program to identify children at high risk for NMDs within the first 30 months of life. The Promoting Early Diagnosis for Neuromuscular Disorders (PEDINE) project implemented a three-step sequential screening in an area of about 300,000 people with (1) an assessment of the motor development milestones to identify “red flags” for NMDs by primary care pediatricians (PCPs) as part of the routine Health Status Check visits; (2) for the children who screened positive, a community neuropsychiatric assessment, with further referral of suspected NMD cases to (3) a hospital-based specialized tertiary care center. In the first-year feasibility study, a total of 10,032 PCP visits were conducted, and twenty children (0.2% of the total Health Status Check visits) screened positive and were referred to the community neuropsychiatrist. Of these, four had elevated creatine kinase (CK) serum levels. This pilot study shows that screening for NMDs in primary care settings is feasible and allows children at high risk for muscular disorder to be promptly identified.

Neonatal presentations of neuromuscular disorders

The term 'neuromuscular diseases' defines disorders of the extended motor unit. Newborns with disorders of peripheral nervous system (PNS) (motor neurons, nerve roots, plexuses, peripheral nerves, neuromuscular junction, and skeletal muscles) present most frequently with hypotonia, weakness, contractures, respiratory and feeding difficulties. Challenge in the newborn period is, hypotonia may also occur with more common central causes such as; electrolyte disturbances, sepsis, hypoxic-ischemic encephalopathy (HIE), congestive heart failure, and inborn errors of metabolism. Moreover, newborns with PNS involvement and/or genetic neuromuscular disorders (NMD) can also be prone to intrapartum asphyxia which further masks an underlying condition. This is why, NMD is also described as one of the 'HIE-mimics'. Genetic counseling, individualized treatment strategies, standards of care require accurate diagnosis. Neuromuscular field is moving to screening programs and pre-symptomatic diagnosis with promising disease-modifying treatments. The aim of this paper is to discuss approach to NMD within the newborn period in line with clinical history, examination findings, and diagnostic tests.

A case for genomic medicine in South African paediatric patients with neuromuscular disease

Paediatric neuromuscular diseases are under-recognised and under-diagnosed in Africa, especially those of genetic origin. This may be attributable to various factors, inclusive of socioeconomic barriers, high burden of communicable and non-communicable diseases, resource constraints, lack of expertise in specialised fields and paucity of genetic testing facilities and biobanks in the African population, making access to and interpretation of results more challenging. As new treatments become available that are effective for specific sub-phenotypes, it is even more important to confirm a genetic diagnosis for affected children to be eligible for drug trials and potential treatments. This perspective article aims to create awareness of the major neuromuscular diseases clinically diagnosed in the South African paediatric populations, as well as the current challenges and possible solutions. With this in mind, we introduce a multi-centred research platform (ICGNMD), which aims to address the limited knowledge on NMD aetiology and to improve genetic diagnostic capacities in South African and other African populations.