Prevalence and health care costs of mitochondrial disease in Ontario, Canada: A population-based cohort study

HPDL Variant Type Correlates With Clinical Disease Onset and Severity

OBJECTIVE

Recently, a mitochondrial encephalopathy due to biallelic HPDL variants was described, associated with a broad range of clinical manifestations ranging from severe, infantile-onset neurodegeneration to adolescence-onset hereditary spastic paraplegia. HPDL converts 4-hydroxyphenylpyruvate acid (4-HPPA) into 4-hydroxymandelate (4-HMA), necessary for the synthesis of the mitochondrial electron transporter CoQ10. This suggests a possible bypass of the metabolic block by 4-HMA treatment; however, genotype-phenotype correlations are lacking.

METHODS

We established an HPDL Patient Registry to prepare for a future clinical trial. Here we report the clinical features of 13 enrolled participants and compare them with 86 previously reported patients. We establish three major clinical classes: severe, intermediate, and mild, presenting onset in early infancy, childhood, and adolescence, respectively. The biallelic genotypes were classified into truncating/truncating, truncating/missense, and missense/missense variants, mapped onto the predicted 3D protein structure, and correlated with severity.

RESULTS

Patients with biallelic truncating variants presented with severe phenotypes and earlier ages of onset. Missense variants were often associated with milder phenotypes, except those with variants predominantly located in or near the VOC2 domain containing iron-binding sites or the C-terminus, which had more severe phenotypes. In addition, p.Met1? variants were also correlated with more severe phenotypes.

INTERPRETATION

This study demonstrates the correlation of age of onset and disease severity with genotype for HPDL-related conditions. Patients with truncating variants and specific missense variants correlated with severe, early-onset features, whereas the presence of at least one missense variant located outside of the iron-binding sites correlated with milder presentations.

TRIAL REGISTRATION

Clinicaltrials.gov HPDL registry: https://clinicaltrials.gov/study/NCT05848271.

A population-based cohort study of mitochondrial disease and mental health conditions in Ontario, Canada

BACKGROUND

Mitochondrial disease has been linked to mental health disorder in clinical cohorts and post-mortem studies. However, a lack of population-level studies examining the relationship between mitochondrial disease and mental health has resulted in an evidence gap and creates a challenge for identifying and addressing care needs for the mitochondrial disease population. Using multiple linked population health databases in a single-payer health system that covers the full population, this study aimed to investigate the prevalence of mood disorders and other mental health conditions in patients with mitochondrial disease and to examine the joint impact of mitochondrial disease and mental health conditions on healthcare use and health system costs. To contextualize these findings, a clinical comparator cohort of multiple sclerosis (MS) patients was analyzed.

RESULTS

Overall, co-prevalent mental health conditions are common in the mitochondrial population. Double the proportion of patients in the mitochondrial disease cohort had a co-prevalent mental health illness as compared to the MS population (18% vs 9%). Healthcare utilization was highest among patients with co-prevalent mitochondrial disease and mental illness, with 49% hospitalized within 1 year prior to cohort entry (compared to 12% of MS patients with no mental health condition). Costs were likewise highest among mitochondrial disease patients with mental health conditions.

CONCLUSIONS

This study presents the first comprehensive, population-wide cohort study of mitochondrial disease and co-prevalent mental health conditions. Our findings demonstrate a high burden of mental health conditions among mitochondrial disease patients, with high associated health care needs. We also find that patients with concurrent mental illness and mitochondrial disease represent a high-burden, high-cost population in a single-payer health insurance setting.

Preliminary investigation on the economic cost of mitochondrial disease in Chinese children

BACKGROUND

The prevalence of mitochondrial diseases is increasing, leading to a significant economic burden on families and society. However, nationwide cost data on their effects on China's economy remain limited. This study aimed to investigate the economic cost of mitochondrial diseases in Chinese children, analyse the relevant influencing factors, and provide a foundation for strategies to reduce the healthcare burden.

METHODS

In this single-centre, cross-sectional study, an online questionnaire was randomly administered to paediatric patients diagnosed with mitochondrial diseases between January 2012 and January 2022. The questionnaire included questions regarding demographic data, clinical information, and expenditure-related costs. Multivariate analysis of economic cost was performed using a generalised linear gamma conjugate model (A1).

RESULTS

The responses to 102 questionnaires were analysed. The median direct economic cost incurred for the diagnosis of mitochondrial disease was $8,520.19, with direct medical and non-medical costs of $6,769.06 and $2,092.98, respectively, and an indirect cost of $3,162.93. Healthcare insurance covers 27.29% of direct medical expenses. Multivariate analysis showed that the economic cost of diagnosing mitochondrial diseases was significantly correlated with the year of disease onset (P < 0.001). The median annual economic cost for treatment and symptom management after diagnosis was $12,292.79, with direct medical and non-medical costs of $10,887.53 and $1,360.44, respectively, and an indirect cost of $5,442.21. Healthcare insurance covered only 15.16% of direct medical expenses. No significant differences were observed between the subgroups after diagnosis and the annual economic costs of treatment or symptom management.

CONCLUSION

The study findings indicated that the economic burden of both the diagnosis and treatment of patients with mitochondrial diseases was substantial. Increased emphasis should be placed on primary and secondary prevention strategies to further reduce the overall economic burden of rare genetic diseases, such as mitochondrial diseases.

Atf3 controls transitioning in female mitochondrial cardiomyopathy as identified by spatial and single-cell transcriptomics

Oxidative phosphorylation defects result in now intractable mitochondrial diseases (MD) with cardiac involvement markedly affecting prognosis. The mechanisms underlying the transition from compensation to dysfunction in response to metabolic deficiency remain unclear. Here, we used spatially resolved transcriptomics and single-nucleus RNA sequencing (snRNA-seq) on the heart of a patient with mitochondrial cardiomyopathy (MCM), combined with an MCM mouse model with cardiac-specific Ndufs6 knockdown (FS6KD). Cardiomyocytes demonstrated the most heterogeneous expression landscape among cell types caused by metabolic perturbation, and pseudotime trajectory analysis revealed dynamic cellular states transitioning from compensation to severe compromise. This progression coincided with the transient up-regulation of a transcription factor, ATF3. Genetic ablation of Atf3 in FS6KD corroborated its pivotal role, effectively delaying cardiomyopathy progression in a female-specific manner. Our findings highlight a fate-determining role of ATF3 in female MCM progression and that the latest transcriptomic analysis will help decipher the mechanisms underlying MD progression.

Improving acute care for Primary Mitochondrial Disease: Development of a publicly available clinical care pathway

Primary mitochondrial diseases (PMD) are an increasingly recognized cause of multi-system organ dysfunction. Children frequently require acute care in an inpatient setting, though many hospitals do not have access to metabolic specialists. We developed a publicly available, evidenced-based clinical pathway utilizing expert consensus guidelines to guide the care of PMD patients during an emergency department visit and/or hospitalization. Utilization of the pathway may help improve triage time, clarify therapeutic options, and help initiate disease-specific screening.

Clinical features and treatment of stroke-like episodes in mitochondrial disease: a cohort-based study

BACKGROUND

Stroke-like episode (SLE) is a subacute evolving brain syndrome in patients with primary mitochondrial diseases. Despite previous research, the understanding of the clinical spectrum, treatment, and outcomes of mitochondrial SLEs is far from complete. In this single centre study, we report the clinical symptoms and radiological findings as well as the medical treatment and outcomes of SLEs in patients with mitochondrial disease.

METHODS

This retrospective, observational study during years 2000-2023 was based on a cohort of patients diagnosed with mitochondrial disease at Turku University Hospital (TUH; Turku, Finland) in the region of Southwest Finland. Data were obtained from the hospital electronic medical record system.

RESULTS

The investigated cohort consisted of 76 patients (37 men, 39 women) with a diagnosis of mitochondrial disease. Among these, 12 patients had a history of at least one SLE; the total number of SLEs was 20. The most common genetic aetiology among patients with SLEs was m.3243A > G (N = 7). The mean age at first SLE was 40 years (range: 5-66 years), and the mean interval between episodes was 4.8 years (range: 4 months-10 years). The duration of episodes varied between 1 and 193 days (median 14 days, mean 37 days); 10 patients needed intensive care unit (ICU) treatment. The mean survival time between the first SLE and death was 3.6 years (range: 0-16 years).

CONCLUSION

Our study highlights the importance of early recognition and prompt management of SLE symptoms, especially epileptic seizures, in this life-threatening entity.

Understanding coenzyme Q

Coenzyme Q (CoQ), also known as ubiquinone, comprises a benzoquinone head group and a long isoprenoid side chain. It is thus extremely hydrophobic and resides in membranes. It is best known for its complex function as an electron transporter in the mitochondrial electron transport chain (ETC) but is also required for several other crucial cellular processes. In fact, CoQ appears to be central to the entire redox balance of the cell. Remarkably, its structure and therefore its properties have not changed from bacteria to vertebrates. In metazoans, it is synthesized in all cells and is found in most, and maybe all, biological membranes. CoQ is also known as a nutritional supplement, mostly because of its involvement with antioxidant defenses. However, whether there is any health benefit from oral consumption of CoQ is not well established. Here we review the function of CoQ as a redox-active molecule in the ETC and other enzymatic systems, its role as a prooxidant in reactive oxygen species generation, and its separate involvement in antioxidant mechanisms. We also review CoQ biosynthesis, which is particularly complex because of its extreme hydrophobicity, as well as the biological consequences of primary and secondary CoQ deficiency, including in human patients. Primary CoQ deficiency is a rare inborn condition due to mutation in CoQ biosynthetic genes. Secondary CoQ deficiency is much more common, as it accompanies a variety of pathological conditions, including mitochondrial disorders as well as aging. In this context, we discuss the importance, but also the great difficulty, of alleviating CoQ deficiency by CoQ supplementation.

Demographic characteristics, diagnostic challenges, treatment patterns, and caregiver burden of mitochondrial diseases: a retrospective cross-sectional study

BACKGROUND

This study aimed to explore the demographic characteristics, diagnostic challenges, treatment patterns, and caregiver burden of mitochondrial diseases.

METHODS

This retrospective cross-sectional study enrolled patients diagnosed with mitochondrial diseases from the Department of Neurology at Peking University First Hospital between January 2010 and December 2021. A questionnaire covering demographic characteristics, diagnostic dilemma, treatment, economic aspects, and caregiver stress was administered, and disability was assessed using the modified Rankin Scale (mRS).

RESULTS

A total of 183 patients (mean age: 16 (IQR: 12-25), 49.72% males) were enrolled, including 124 pediatric patients and 59 adult patients. MELAS (106. 57.92%) and Leigh syndrome (37, 20.22%) were predominant among the mitochondrial disease subtypes. Among them, 132 (72.13%) patients were initially misdiagnosed with other diseases, 58 (31.69%) patients visited 2 hospitals before confirmed as mitochondrial disease, and 39 (21.31%) patients visited 3 hospitals before confirmed as mitochondrial disease. Metabolic modifiers were the most common type of drugs used, including several dietary supplements such as L-carnitine (117, 63.93%), Coenzyme Q10 (102, 55.74%), idebenone (82, 44.81%), and vitamins (99, 54.10%) for proper mitochondrial function. Mothers are the primary caregivers for both children (36.29%) and adults (38.98%). The mRS score ranged from 0 to 5, 92.35% of the patients had different degrees of disability due to mitochondrial disease. The average monthly treatment cost was 3000 RMB for children and 3100 RMB for adults.

CONCLUSIONS

This study provided valuable insights into the characteristics and challenges of mitochondrial diseases, which underscores the need for improved awareness, diagnostic efficiency, and comprehensive support for patients and caregivers.

Epidemiology and natural history of POLG disease in Norway: a nationwide cohort study

OBJECTIVE

To investigate the prevalence and natural history of POLG disease in the Norwegian population.

METHODS

A national, population-based, retrospective study using demographic, clinical, and genetic data of patients with genetically confirmed POLG disease. The patients were diagnosed between 2002 and 2022, and were included into the Norwegian POLG Patient Registry. Patients were stratified according to age at disease onset (early <12 years, juvenile to adult 12-40 years, late ≥40 years) and resident region.

RESULTS

Ninety-one patients were included. The point prevalence of POLG disease was 1:149,253. Birth prevalence was 1:48,780. Median age at clinical onset was 16 years (range: 2 months to 70 years). Onset occurred early in 35% (32 out of 91), juvenile-adult in 55% (50 out of 91) and late in 10% (9 out of 91). A distinct seasonal pattern in disease onset was observed, with 57% (52 out of 91) presenting between May and August. Forty-five patients (49%) had acute exacerbations that required intensive care, and this affected 72% of those in the early-onset group. The mortality rate was 54% (49 out of 91), with a median time from disease onset to death of 3 years (range: 1 month to 36 years).

INTERPRETATION

We provide the point prevalence and birth prevalence of POLG disease in the first nationwide study in which epidemiological and clinical data were integrated. Seasonal variations in clinical onset may offer valuable insights into disease mechanisms and modifying factors. The findings from this study are crucial for quantifying the disease burden, and contribute to evidence-based healthcare planning.

Clinical drivers of hospitalisation in patients with mitochondrial diseases

Background

Mitochondrial diseases in adults are generally chronic conditions with a wide spectrum of severity contributing to disease burden and healthcare resource utilisation. Data on healthcare resource utilisation in mitochondrial diseases are limited.

Objectives

We performed a retrospective longitudinal study to investigate the clinical drivers of hospitalisation in adult patients with mitochondrial diseases to better understand healthcare resource utilisation.

Methods

We recruited participants from our specialised Mitochondrial Disease Clinic in Sydney, Australia between September 2018 and December 2021. We performed a retrospective chart review for the period 2013-2022 considering emergency department (ED) and/or hospital admission notes, as well as discharge summaries. We used multiple linear regression models to examine the association between the type of presenting symptom(s) and duration of hospital stay and frequency of admissions, while adjusting for relevant covariates.

Results

Of the 99 patients considered, the duration of hospitalisation ranged from 0 to 116 days per participant and the number of admissions ranged from 0 to 21 per participant. Participants with one or more mitochondrial disease-associated admissions constituted 52% of the study cohort. 13% of the participants presented to the ED without requiring an admission and 35% never attended the ED or required a hospital admission during this period. Neurological (p<0.0001), gastroenterological (p=0.01) and symptoms categorised as 'other' (p<0.0001) were the main presentations driving the total number of days admitted to hospital. A statistically significant association was evident for the number of admissions and all types of presenting symptoms (p<0.0001).

Conclusion

There are variable reasons for hospitalisation in adults with mitochondrial diseases, with neurological and gastroenterological presentations being associated with prolonged and complex hospitalisation. A better understanding of clinical drivers such as these allows for better informed and well-coordinated management aimed at optimising healthcare resource utilisation.

Hydrogen sulfide supplementation as a potential treatment for primary mitochondrial diseases

Primary mitochondrial diseases (PMD) are amongst the most common inborn errors of metabolism causing fatal outcomes within the first decade of life. With marked heterogeneity in both inheritance patterns and physiological manifestations, these conditions present distinct challenges for targeted drug therapy, where effective therapeutic countermeasures remain elusive within the clinic. Hydrogen sulfide (H2S)-based therapeutics may offer a new option for patient treatment, having been proposed as a conserved mitochondrial substrate and post-translational regulator across species, displaying therapeutic effects in age-related mitochondrial dysfunction and neurodegenerative models of mitochondrial disease. H2S can stimulate mitochondrial respiration at sites downstream of common PMD-defective subunits, augmenting energy production, mitochondrial function and reducing cell death. Here, we highlight the primary signalling mechanisms of H2S in mitochondria relevant for PMD and outline key cytoprotective proteins/pathways amenable to post-translational restoration via H2S-mediated persulfidation. The mechanisms proposed here, combined with the advent of potent mitochondria-targeted sulfide delivery molecules, could provide a framework for H2S as a countermeasure for PMD disease progression.

Current management of primary mitochondrial disorders in EU countries: the European Reference Networks survey

BACKGROUND AND PURPOSE

Primary mitochondrial diseases (PMDs) are rare diseases for which diagnosis is challenging, and management and training programs are not well defined in Europe. To capture and assess care needs, five different European Reference Networks have conducted an exploratory survey.

METHODS

The survey covering multiple topics relating to PMDs was sent to all ERNs healthcare providers (HCPs) in Europe.

RESULTS

We have collected answers from 220 members based in 24/27 European member states and seven non-European member states. Even though most of the responders are aware of neurogenetic diseases, difficulties arise in the ability to deliver comprehensive genetic testing. While single gene analysis is widely available in Europe, whole exome and genome sequencing are not easily accessible, with considerable variation between countries and average waiting time for results frequently above 6 months. Only 12.7% of responders were happy with the ICD-10 codes for classifying patients with PMDs discharged from the hospital, and more than 70% of them consider that PMDs deserve specific ICD codes to improve clinical management, including tailored healthcare, and for reimbursement reasons. Finally, 90% of responders declared that there is a need for further education and training in these diseases.

CONCLUSIONS

This survey provides information on the current difficulties in the care of PMDs in Europe. We believe that the results of this survey are important to help rare disease stakeholders in European countries identify key care and research priorities.

The burden of mitochondrial disease with associated seizures: systematic literature reviews of health-related quality of life, utilities, costs and healthcare resource use data

BACKGROUND

Mitochondrial disease is a degenerative, progressive, heterogeneous group of genetic disorders affecting children and adults. Mitochondrial disease is associated with morbidity and mortality, with predominantly neurological and neuromuscular symptoms including dystonia, weakness, encephalopathy, developmental delay and seizures. Seizures are one of the most common and severe manifestations of mitochondrial disease. These seizures are typically refractory to common anti-seizure therapies. There are no approved disease-modifying treatments for mitochondrial disease. Our objective was to conduct two systematic literature reviews to identify health-related quality of life (HRQoL), utilities, costs and healthcare resource use data in mitochondrial disease with associated seizures.

METHODS

A range of databases and information sources were searched up to July 2022 to identify eligible studies. Search strategies included a range of variant terms for mitochondrial disease and HRQoL, utilities, cost and healthcare resource use outcomes. Two reviewers independently assessed articles against the eligibility criteria; studies were extracted by one reviewer and checked by a second. Risk of bias was assessed for studies reporting HRQoL data. Results were narratively assessed.

RESULTS

Seven studies were eligible for the HRQoL and utilities review. The studies used different tools to report data, and despite the variability in methods, HRQoL scores across the studies showed moderate/severe disease in patients with mitochondrial disease with associated seizures. Parents of patients with mitochondrial disease with associated seizures were characterised by high total parenting stress. No studies reported utilities data. Two case reports and one retrospective review of medical records of children who died in hospital were eligible for the costs and resource use review. These provided limited information on the duration of hospital stay, in an intensive care unit (ICU), on mechanical ventilation. No studies reported costs data.

CONCLUSION

These reviews highlight the limited HRQoL, utilities, costs and resource use data and the variability of instruments used in mitochondrial disease with associated seizures. However, the data available indicate that mitochondrial disease with associated seizures affects patients' and caregivers' HRQoL alike. No robust conclusion can be drawn on the impact of mitochondrial disease with associated seizures on hospital or ICU length of stay. Trial registration PROSPERO: CRD42022345005.

Mitochondrial Properties in Skeletal Muscle Fiber

Mitochondria are the primary source of energy production and are implicated in a wide range of biological processes in most eukaryotic cells. Skeletal muscle heavily relies on mitochondria for energy supplements. In addition to being a powerhouse, mitochondria evoke many functions in skeletal muscle, including regulating calcium and reactive oxygen species levels. A healthy mitochondria population is necessary for the preservation of skeletal muscle homeostasis, while mitochondria dysregulation is linked to numerous myopathies. In this review, we summarize the recent studies on mitochondria function and quality control in skeletal muscle, focusing mainly on in vivo studies of rodents and human subjects. With an emphasis on the interplay between mitochondrial functions concerning the muscle fiber type-specific phenotypes, we also discuss the effect of aging and exercise on the remodeling of skeletal muscle and mitochondria properties.

Healthcare resource utilization of patients with mitochondrial disease in an outpatient hospital setting

BACKGROUND AND OBJECTIVES

Mitochondrial diseases present as multi-system disorders requiring a comprehensive multidisciplinary approach. The data on healthcare resource utilization associated with mitochondrial diseases and the clinical drivers of these costs are limited including for the out-patient setting where the majority of the clinical care for mitochondrial disease patients occurs. We performed a cross-sectional retrospective study of out-patient healthcare resource utilization and costs for patients with a confirmed diagnosis of mitochondrial disease.

METHODS

We recruited participants from the Mitochondrial Disease Clinic in Sydney and stratified them into three groups: those with mitochondrial DNA (mtDNA) mutations (Group 1), those with nuclear DNA (nDNA) mutations and the predominant phenotype of chronic progressive external ophthalmoplegia (CPEO) or optic atrophy (Group 2) and those without a confirmed genetic diagnosis but clinical criteria and muscle biopsy findings supportive of a diagnosis of mitochondrial disease (Group 3). Data was collected through retrospective chart review and out-patient costs were calculated using the Medicare Benefits Schedule.

RESULTS

We analyzed the data from 91 participants and found that Group 1 had the greatest average out-patient costs per person per annum ($838.02; SD 809.72). Neurological investigations were the largest driver of outpatient healthcare costs in all groups (average costs per person per annum:-Group 1: $364.11; SD 340.93, Group 2: $247.83; SD 113.86 and Group 3: $239.57; SD 145.69) consistent with the high frequency (94.5%) of neurological symptoms. Gastroenterological and cardiac-related out-patient costs were also major contributors to out-patient healthcare resource utilization in Groups 1 and 3. In Group 2, ophthalmology was the second-most resource intensive specialty ($136.85; SD 173.35). The Group 3 had the greatest average healthcare resource utilization per person over the entire duration of out-patient clinic care ($5815.86; SD 3520.40) most likely due to the lack of a molecular diagnosis and a less customized management approach.

CONCLUSION

The drivers of healthcare resource utilization are dependent on the phenotype-genotype characteristics. Neurological, cardiac, and gastroenterological costs were the top three drivers in the out-patient clinics unless the patient had nDNA mutations with predominant phenotype of CPEO and/or optic atrophy wherein ophthalmological-related costs were the second most resource intensive driver.