Helping the World Achieve Sustainable Development Goals: The Role of PNPs and Pediatric-Focused Providers.

In 2015 the United Nations created the Agenda for Sustainable Development and a list of 17 sustainable development goals (SDGs) for 2030. This year is the halfway mark toward meeting the goals, and the results reported by the World Health Organization in 2023 are not as positive as hoped, as progress has stagnated. The third SDG primarily focuses on the health and well-being of all ages to prevent unavoidable deaths in children aged < 5 years. Pediatric nurse practitioners are uniquely positioned to support programs building toward the health and well-being of children. Becoming aware of opportunities will help pediatric nurse practitioners use their voices toward success in meeting the SDGs.

Enhanced mitochondrial genome analysis: bioinformatic and long-read sequencing advances and their diagnostic implications.

INTRODUCTION: Primary mitochondrial diseases (PMDs) comprise a large and heterogeneous group of genetic diseases that result from pathogenic variants in either nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). Widespread adoption of next-generation sequencing (NGS) has improved the efficiency and accuracy of mtDNA diagnoses; however, several challenges remain. AREAS COVERED: In this review, we briefly summarize the current state of the art in molecular diagnostics for mtDNA and consider the implications of improved whole genome sequencing (WGS), bioinformatic techniques, and the adoption of long-read sequencing, for PMD diagnostics. EXPERT OPINION: We anticipate that the application of PCR-free WGS from blood DNA will increase in diagnostic laboratories, while for adults with myopathic presentations, WGS from muscle DNA may become more widespread. Improved bioinformatic strategies will enhance WGS data interrogation, with more accurate delineation of mtDNA and NUMTs (nuclear mitochondrial DNA segments) in WGS data, superior coverage uniformity, indirect measurement of mtDNA copy number, and more accurate interpretation of heteroplasmic large-scale rearrangements (LSRs). Separately, the adoption of diagnostic long-read sequencing could offer greater resolution of complex LSRs and the opportunity to phase heteroplasmic variants.

Mitochondria generate our bodies' energy, and they contain their own circular DNA molecules. Changes in this mitochondrial DNA can cause a wide range of genetic diseases. Improved computer processing of the sequence of this DNA and new techniques that can read the full DNA sequence in one experiment may enhance our ability to understand these genetic variants.

Genetic testing for mitochondrial disease: the United Kingdom best practice guidelines.

Primary mitochondrial disease describes a diverse group of neuro-metabolic disorders characterised by impaired oxidative phosphorylation. Diagnosis is challenging; >350 genes, both nuclear and mitochondrial DNA (mtDNA) encoded, are known to cause mitochondrial disease, leading to all possible inheritance patterns and further complicated by heteroplasmy of the multicopy mitochondrial genome. Technological advances, particularly next-generation sequencing, have driven a shift in diagnostic practice from 'biopsy first' to genome-wide analyses of blood and/or urine DNA. This has led to the need for a reference framework for laboratories involved in mitochondrial genetic testing to facilitate a consistent high-quality service. In the United Kingdom, consensus guidelines have been prepared by a working group of Clinical Scientists from the NHS Highly Specialised Service followed by national laboratory consultation. These guidelines summarise current recommended technologies and methodologies for the analysis of mtDNA and nuclear-encoded genes in patients with suspected mitochondrial disease. Genetic testing strategies for diagnosis, family testing and reproductive options including prenatal diagnosis are outlined. Importantly, recommendations for the minimum levels of mtDNA testing for the most common referral reasons are included, as well as guidance on appropriate referrals and information on the minimal appropriate gene content of panels when analysing nuclear mitochondrial genes. Finally, variant interpretation and recommendations for reporting of results are discussed, focussing particularly on the challenges of interpreting and reporting mtDNA variants.

Specialist multidisciplinary input maximises rare disease diagnoses from whole genome sequencing.

Diagnostic whole genome sequencing (WGS) is increasingly used in rare diseases. However, standard, semi-automated WGS analysis may overlook diagnoses in complex disorders. Here, we show that specialist multidisciplinary analysis of WGS, following an initial 'no primary findings' (NPF) report, improves diagnostic rates and alters management. We undertook WGS in 102 adults with diagnostically challenging primary mitochondrial disease phenotypes. NPF cases were reviewed by a genomic medicine team, thus enabling bespoke informatic approaches, co-ordinated phenotypic validation, and functional work. We enhanced the diagnostic rate from 16.7% to 31.4%, with management implications for all new diagnoses, and detected strong candidate disease-causing variants in a further 3.9% of patients. This approach presents a standardised model of care that supports mainstream clinicians and enhances diagnostic equity for complex disorders, thereby facilitating access to the potential benefits of genomic healthcare. This research was made possible through access to the data and findings generated by the 100,000 Genomes Project: http://www.genomicsengland.co.uk .

Mitochondrial Strokes: Diagnostic Challenges and Chameleons.

Mitochondrial stroke-like episodes (SLEs) are a hallmark of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). They should be suspected in anyone with an acute/subacute onset of focal neurological symptoms at any age and are usually driven by seizures. Suggestive features of an underlying mitochondrial pathology include evolving MRI lesions, often originating within the posterior brain regions, the presence of multisystemic involvement, including diabetes, deafness, or cardiomyopathy, and a positive family history. The diagnosis of MELAS has important implications for those affected and their relatives, given it enables early initiation of appropriate treatment and genetic counselling. However, the diagnosis is frequently challenging, particularly during the acute phase of an event. We describe four cases of mitochondrial strokes to highlight the considerable overlap that exists with other neurological disorders, including viral and autoimmune encephalitis, ischemic stroke, and central nervous system (CNS) vasculitis, and discuss the clinical, laboratory, and imaging features that can help distinguish MELAS from these differential diagnoses.

Diagnosing Mitochondrial Disorders Remains Challenging in the Omics Era.

OBJECTIVE: We hypothesized that novel investigative pathways are needed to decrease diagnostic odysseys in pediatric mitochondrial disease and sought to determine the utility of clinical exome sequencing in a large cohort with suspected mitochondrial disease and to explore whether any of the traditional indicators of mitochondrial disease predict a confirmed genetic diagnosis. METHODS: We investigated a cohort of 85 pediatric patients using clinical exome sequencing and compared the results with the outcome of traditional diagnostic tests, including biochemical testing of routine parameters (lactate, alanine, and proline), neuroimaging, and muscle biopsy with histology and respiratory chain enzyme activity studies. RESULTS: We established a genetic diagnosis in 36.5% of the cohort and report 20 novel disease-causing variants (1 mitochondrial DNA). Counterintuitively, routine biochemical markers were more predictive of mitochondrial disease than more invasive and elaborate muscle studies. CONCLUSIONS: We propose using biochemical markers to support the clinical suspicion of mitochondrial disease and then apply first-line clinical exome sequencing to identify a definite diagnosis. Muscle biopsy studies should only be used in clinically urgent situations or to confirm an inconclusive genetic result. CLASSIFICATION OF EVIDENCE: This is a Class II diagnostic accuracy study showing that the combination of CSF and plasma biochemical tests plus neuroimaging could predict the presence or absence of exome sequencing confirmed mitochondrial disorders.

Mitochondrial DNA Analysis from Exome Sequencing Data Improves Diagnostic Yield in Neurological Diseases.

A rapidly expanding catalog of neurogenetic disorders has encouraged a diagnostic shift towards early clinical whole exome sequencing (WES). Adult primary mitochondrial diseases (PMDs) frequently exhibit neurological manifestations that overlap with other nervous system disorders. However, mitochondrial DNA (mtDNA) is not routinely analyzed in standard clinical WES bioinformatic pipelines. We reanalyzed 11,424 exomes, enriched with neurological diseases, for pathogenic mtDNA variants. Twenty-four different mtDNA mutations were detected in 64 exomes, 11 of which were considered disease causing based on the associated clinical phenotypes. These findings highlight the diagnostic uplifts gained by analyzing mtDNA from WES data in neurological diseases. ANN NEUROL 2021;89:1240-1247.

A Quality Improvement Initiative to Reduce Surgical Site Infections in Patients Undergoing Delayed Sternal Closure After Pediatric Cardiac Surgery.

Sternal wound infections (SWI) in delayed sternal closure (DSC) patients are a healthcare burden after congenital heart surgery. There are no guidelines specific for pediatric DSC patients to prevent this costly complication. The hypothesis was that the modifications to a bundled approach for DSC patients would decrease the SWI rate. For this prospective cohort study, DSC patients were postoperatively admitted to a pediatric cardiac care unit from February 2017 to January 2018. Using a modified protocol for prevention of SWI, the infection rates pre- and post-modified protocol were compared. The primary outcome measure was SWI. Secondary outcome measures were compliance with modifications. Retrospective review of cases in pre-protocol modification era from January 1, 2014 to December 31, 2016 showed 377 pediatric cardiopulmonary bypass cases and 39 (10.4%) underwent DSC. During the post-protocol modification era, there were 129 cardiopulmonary bypass cases and 17 (13%) DSC cases. The SWI rate in DSC were 7.7% and 0% for pre-intervention and post-intervention, respectively (p = 0.52). The Bayesian confidence interval with Jeffreys prior gives a 95% confidence interval of 1.5% to 18.3% for pre-intervention and 0 to 13.5% for post-intervention. Compliance with the protocol bundle during the post protocol era was 93-100%. Although preliminary results are not statistically significant due to cohort size, the economic burden and increased LOS for each SWI is clinically significant. The early results of reduced infections for DSC patients using a modified bundle approach appear promising. Continued study and a multicenter project would be beneficial.

Efforts to Reduce Infections in Delayed Sternal Closure Patients: A Survey of Pediatric Practice.

BACKGROUND: Pediatric patients with sternum left open after cardiac surgery experience a higher risk for sternal wound infection (SWI). These infections are costly for programs, payers, and patients and their families. Despite efforts by individual programs to reduce infections in patients undergoing delayed sternal closure (DSC), there are no established guidelines that address preventive procedures. The purpose of this study was to determine the practice of pediatric cardiac surgery programs to prevent infection in their DSC patients and if preventive measures were associated with less infections. METHODS: A 33 question survey on institutional practices was sent to chief surgeons at pediatric cardiac surgery programs in the United States. RESULTS: Twenty-eight (35%) surgical programs responded. The mean number of pediatric cardiac bypass operations performed by programs in 2016 was 227 (range: 69-872). Data represented 6,484 patients <18 years of age who underwent cardiac surgery with 807 (12%) of those undergoing DSC. One hundred fifty-eight (2.4%) of all patients and 51 (6.3%) of the DSC patients developed a SWI. Patients with DSC who received preoperative baths were less likely to become infected (5.9% vs 15.8%; P = .015). Patients in programs with feeding protocols had fewer infections (5.7% vs 14.8%; P = .008). CONCLUSIONS: The results of this survey of children's cardiac surgery programs describe their practices to reduce infection rates in DSC patients. A multicenter project on wound care and closure techniques that might impact this costly complication is needed.

Expanding the molecular and phenotypic spectrum of truncating MT-ATP6 mutations.

OBJECTIVE: To describe the clinical and functional consequences of 1 novel and 1 previously reported truncating MT-ATP6 mutation. METHODS: Three unrelated probands with mitochondrial encephalomyopathy harboring truncating MT-ATP6 mutations are reported. Transmitochondrial cybrid cell studies were used to confirm pathogenicity of 1 novel variant, and the effects of all 3 mutations on ATPase 6 and complex V structure and function were investigated. RESULTS: Patient 1 presented with adult-onset cerebellar ataxia, chronic kidney disease, and diabetes, whereas patient 2 had myoclonic epilepsy and cerebellar ataxia; both harbored the novel m.8782G>A; p.(Gly86*) mutation. Patient 3 exhibited cognitive decline, with posterior white matter abnormalities on brain MRI, and severely impaired renal function requiring transplantation. The m.8618dup; p.(Thr33Hisfs*32) mutation, previously associated with neurogenic muscle weakness, ataxia, and retinitis pigmentosa, was identified. All 3 probands demonstrated a broad range of heteroplasmy across different tissue types. Blue-native gel electrophoresis of cultured fibroblasts and skeletal muscle tissue confirmed multiple bands, suggestive of impaired complex V assembly. Microscale oxygraphy showed reduced basal respiration and adenosine triphosphate synthesis, while reactive oxygen species generation was increased. Transmitochondrial cybrid cell lines studies confirmed the deleterious effects of the novel m.8782 G>A; p.(Gly86*) mutation. CONCLUSIONS: We expand the clinical and molecular spectrum of MT-ATP6-related mitochondrial disorders to include leukodystrophy, renal disease, and myoclonic epilepsy with cerebellar ataxia. Truncating MT-ATP6 mutations may exhibit highly variable mutant levels across different tissue types, an important consideration during genetic counseling.

Utility of Whole Blood Thiamine Pyrophosphate Evaluation in TPK1-Related Diseases.

TPK1 mutations are a rare, but potentially treatable, cause of thiamine deficiency. Diagnosis is challenging given the phenotypic overlap that exists with other metabolic and neurological disorders. We report a case of TPK1-related disease presenting with Leigh-like syndrome and review the diagnostic utility of thiamine pyrophosphate (TPP) blood measurement. The proband, a 35-year-old male, presented at four months of age with recurrent episodes of post-infectious encephalopathy. He subsequently developed epilepsy, learning difficulties, sensorineural hearing loss, spasticity, and dysphagia. There was a positive family history for Leigh syndrome in an older brother. Plasma lactate was elevated (3.51 mmol/L) and brain MRI showed bilateral basal ganglia hyperintensities, indicative of Leigh syndrome. Histochemical and spectrophotometric analysis of mitochondrial respiratory chain complexes I, II+III, and IV was normal. Genetic analysis of muscle mitochondrial DNA was negative. Whole exome sequencing of the proband confirmed compound heterozygous variants in TPK1: c. 426G>C (p. Leu142Phe) and c. 258+1G>A (p.?). Blood TPP levels were reduced, providing functional evidence for the deleterious effects of the variants. We highlight the clinical and bioinformatics challenges to diagnosing rare genetic disorders and the continued utility of biochemical analyses, despite major advances in DNA sequencing technology, when investigating novel, potentially disease-causing, genetic variants. Blood TPP measurement represents a fast and cost-effective diagnostic tool in TPK1-related diseases.

Pathogenic variants in MT-ATP6: A United Kingdom-based mitochondrial disease cohort study.

Distinct clinical syndromes have been associated with pathogenic MT-ATP6 variants. In this cohort study, we identified 125 individuals (60 families) including 88 clinically affected individuals and 37 asymptomatic carriers. Thirty-one individuals presented with Leigh syndrome and 7 with neuropathy ataxia retinitis pigmentosa. The remaining 50 patients presented with variable nonsyndromic features including ataxia, neuropathy, and learning disability. We confirmed maternal inheritance in 39 families and demonstrated that tissue segregation patterns and phenotypic threshold are variant dependent. Our findings suggest that MT-ATP6-related mitochondrial DNA disease is best conceptualized as a mitochondrial disease spectrum disorder and should be routinely included in genetic ataxia and neuropathy gene panels. ANN NEUROL 2019;86:310-315.

MRPS25 mutations impair mitochondrial translation and cause encephalomyopathy.

Mitochondrial disorders are clinically and genetically heterogeneous and are associated with a variety of disease mechanisms. Defects of mitochondrial protein synthesis account for the largest subgroup of disorders manifesting with impaired respiratory chain capacity; yet, only a few have been linked to dysfunction in the protein components of the mitochondrial ribosomes. Here, we report a subject presenting with dyskinetic cerebral palsy and partial agenesis of the corpus callosum, while histochemical and biochemical analyses of skeletal muscle revealed signs of mitochondrial myopathy. Using exome sequencing, we identified a homozygous variant c.215C>T in MRPS25, which encodes for a structural component of the 28S small subunit of the mitochondrial ribosome (mS25). The variant segregated with the disease and substitutes a highly conserved proline residue with leucine (p.P72L) that, based on the high-resolution structure of the 28S ribosome, is predicted to compromise inter-protein contacts and destabilize the small subunit. Concordant with the in silico analysis, patient's fibroblasts showed decreased levels of MRPS25 and other components of the 28S subunit. Moreover, assembled 28S subunits were scarce in the fibroblasts with mutant mS25 leading to impaired mitochondrial translation and decreased levels of multiple respiratory chain subunits. Crucially, these abnormalities were rescued by transgenic expression of wild-type MRPS25 in the mutant fibroblasts. Collectively, our data demonstrate the pathogenicity of the p.P72L variant and identify MRPS25 mutations as a new cause of mitochondrial translation defect.

Adult-onset Leigh syndrome linked to the novel stop codon mutation m.6579G>A in MT-CO1.

Adult-onset Leigh syndrome is a rare but important manifestation of mitochondrial disease. We report a 17 year old female who presented with subacute encephalopathy, brainstem and extrapyramidal signs, raised CSF lactate, and symmetrical hyperintensities in the basal ganglia on T2-weighted cerebral MRI. The presence of cytochrome c oxidase deficient fibres in muscle tissue prompted sequencing of the entire mitochondrial genome which revealed the novel stop codon mutation m.6579G>A; p.Gly226X in MT-CO1. Here we present the case and review the clinicopathological and molecular spectrum of previously reported MT-CO1 truncating mutations.

Multicenter Quality Improvement Project to Prevent Sternal Wound Infections in Pediatric Cardiac Surgery Patients.

BACKGROUND: Children undergoing cardiac surgery are at risk for sternal wound infections (SWIs) leading to increased morbidity and mortality. Single-center quality improvement (QI) initiatives have demonstrated decreased infection rates utilizing a bundled approach. This multicenter project was designed to assess the efficacy of a protocolized approach to decrease SWI. METHODS: Pediatric cardiac programs joined a collaborative effort to prevent SWI. Programs implemented the protocol, collected compliance data, and provided data points from local clinical registries using Society of Thoracic Surgery Congenital Heart Surgery Database harvest-compliant software or from other registries. RESULTS: Nine programs prospectively collected compliance data on 4,198 children. Days between infections were extended from 68.2 days (range: 25-82) to 130 days (range: 43-412). Protocol compliance increased from 76.7% (first quarter) to 91.3% (final quarter). Ninety (1.9%) children developed an SWI preprotocol and 64 (1.5%) postprotocol, P = .18. The 657 (15%) delayed sternal closure patients had a 5% infection rate with 18 (5.7%) in year 1 and 14 (4.3%) in year 2 P = .43. Delayed sternal closure patients demonstrated a trend toward increased risk for SWI of 1.046 for each day the sternum remained open, P = .067. Children who received appropriately timed preop antibiotics developed less infections than those who did not, 1.9% versus 4.1%, P = .007. CONCLUSION: A multicenter QI project to reduce pediatric SWIs demonstrated an extension of days between infections and a decrease in SWIs. Patients who received preop antibiotics on time had lower SWI rates than those who did not.

Clinicopathologic and molecular spectrum of RNASEH1-related mitochondrial disease.

OBJECTIVE: Pathologic ribonuclease H1 (RNase H1) causes aberrant mitochondrial DNA (mtDNA) segregation and is associated with multiple mtDNA deletions. We aimed to determine the prevalence of RNase H1 gene (RNASEH1) mutations among patients with mitochondrial disease and establish clinically meaningful genotype-phenotype correlations. METHODS: RNASEH1 was analyzed in patients with (1) multiple deletions/depletion of muscle mtDNA and (2) mendelian progressive external ophthalmoplegia (PEO) with neuropathologic evidence of mitochondrial dysfunction, but no detectable multiple deletions/depletion of muscle mtDNA. Clinicopathologic and molecular evaluation of the newly identified and previously reported patients harboring RNASEH1 mutations was subsequently undertaken. RESULTS: Pathogenic c.424G>A p.Val142Ile RNASEH1 mutations were detected in 3 pedigrees among the 74 probands screened. Given that all 3 families had Indian ancestry, RNASEH1 genetic analysis was undertaken in 50 additional Indian probands with variable clinical presentations associated with multiple mtDNA deletions, but no further RNASEH1 mutations were confirmed. RNASEH1-related mitochondrial disease was characterized by PEO (100%), cerebellar ataxia (57%), and dysphagia (50%). The ataxia neuropathy spectrum phenotype was observed in 1 patient. Although the c.424G>A p.Val142Ile mutation underpins all reported RNASEH1-related mitochondrial disease, haplotype analysis suggested an independent origin, rather than a founder event, for the variant in our families. CONCLUSIONS: In our cohort, RNASEH1 mutations represent the fourth most common cause of adult mendelian PEO associated with multiple mtDNA deletions, following mutations in POLG, RRM2B, and TWNK. RNASEH1 genetic analysis should also be considered in all patients with POLG-negative ataxia neuropathy spectrum. The pathophysiologic mechanisms by which the c.424G>A p.Val142Ile mutation impairs human RNase H1 warrant further investigation.