bims-curels Biomed News
on Leigh syndrome
Issue of 2024‒04‒07
five papers selected by
Cure Mito Foundation

  1. Eur J Neurol. 2024 Apr 04. e16275
      BACKGROUND AND PURPOSE: Primary mitochondrial diseases (PMDs) are common inborn errors of energy metabolism, with an estimated prevalence of one in 4300. These disorders typically affect tissues with high energy requirements, including heart, muscle and brain. Epilepsy may be the presenting feature of PMD, can be difficult to treat and often represents a poor prognostic feature. The aim of this study was to develop guidelines and consensus recommendations on safe medication use and seizure management in mitochondrial epilepsy.METHODS: A panel of 24 experts in mitochondrial medicine, pharmacology and epilepsy management of adults and/or children and two patient representatives from seven countries was established. Experts were members of five different European Reference Networks, known as the Mito InterERN Working Group. A Delphi technique was used to allow the panellists to consider draft recommendations on safe medication use and seizure management in mitochondrial epilepsy, using two rounds with predetermined levels of agreement.
    RESULTS: A high level of consensus was reached regarding the safety of 14 out of all 25 drugs reviewed, resulting in endorsement of National Institute for Health and Care Excellence guidelines for seizure management, with some modifications. Exceptions including valproic acid in POLG disease, vigabatrin in patients with γ-aminobutyric acid transaminase deficiency and topiramate in patients at risk for renal tubular acidosis were highlighted.
    CONCLUSIONS: These consensus recommendations describe our intent to improve seizure control and reduce the risk of drug-related adverse events in individuals living with PMD-related epilepsy.
    Keywords:  consensus; epilepsy; management; mitochondrial diseases; recommendations
  2. Mol Genet Metab Rep. 2024 Jun;39 101078
      Leigh syndrome is a severe progressive mitochondrial disorder mainly affecting children under the age of 5 years. It is caused by pathogenic variants in any one of more than 75 known genes in the nuclear or mitochondrial genomes. A 19-week-old male infant presented with lactic acidosis and encephalopathy following a 2-week history of irritability, neuroregression and poor weight gain. He was hypotonic with pathological reflexes, impaired vision, and nystagmus. Brain MRI showed extensive bilateral symmetrical T2 hyperintense lesions in basal ganglia, thalami, and brainstem. Metabolic workup showed elevated serum alanine, and heavy lactic aciduria with increased ketones, fumarate, malate, and alpha-ketoglutarate as well as reduced succinate on urine organic acid analysis. Lactic acidemia persisted, with only a marginally elevated lactate:pyruvate ratio (16.46, ref. 0-10). He demised at age 7 months due to respiratory failure. Exome sequencing followed by virtual gene panel analysis for pyruvate metabolism and mitochondrial defects could not identify any nuclear cause for Leigh syndrome. Mitochondrial DNA (mtDNA) genome sequencing revealed 88% heteroplasmy for a novel variant, NC_012920.1(MT-ND6):m.14430A>C p.(Trp82Gly), in blood DNA. This variant was absent from the unaffected mother's blood, fibroblast, and urine DNA, and detected at a level of 5% in her muscle DNA. Mitochondrial respiratory chain analysis revealed markedly reduced mitochondrial complex I activity in patient fibroblasts (34% of parent and control cells), and reduced NADH-linked respirometry (less than half of parental and control cells), while complex II driven respirometry remained intact. The combined clinical, genetic, and biochemical findings suggest that the novel MT-ND6 variant is the likely cause of Leigh syndrome in this patient. The mitochondrial ND6 protein is a subunit of complex I. An interesting finding was the absence of a significantly elevated lactate:pyruvate ratio in the presence of severe lactatemia, which directed initial diagnostic efforts towards excluding a pyruvate metabolism defect. This case highlights the value of a multidisciplinary approach and complete genetic workup to diagnosing mitochondrial disorders in South African patients.
    Keywords:  Complex I deficiency; Leigh syndrome; MT-DN6; Novel mtDNA variant
  3. J Genet Couns. 2024 Apr 01.
      Ultra rare disorders are being diagnosed at an unprecedented rate, due to genomic sequencing. These diagnoses are often a new gene association, for which little is known, and few share the diagnosis. For these diagnoses, we use the term emerging-ultrarare disorder (E-URD), defined as <100 diagnosed individuals. We contacted 20 parents of children diagnosed with an E-URD through the Duke University Research Sequencing Clinic. Seventeen completed semi-structured interviews exploring parental perspectives (7/17 had children in publications describing the phenotype; 4/17 had children in the first publication establishing a new disorder). Data were analyzed using a directed content approach informed by an empowerment framework. Parents reported a range of responses, including benefits of a diagnosis and challenges of facing the unknown, some described feeling lost and confused, while others expressed empowerment. Empowerment characteristics were hope for the future, positive emotions, engagement, and confidence/self-efficacy to connect with similar others, partner with healthcare providers, and seek new knowledge. We identified a subset of parents who proactively engaged researchers, supported research and publications, and created patient advocacy and support organizations to connect with and bolster similarly diagnosed families. Other parents reported challenges of low social support, low tolerance for uncertainty, limited knowledge about their child's disorder, as well as difficulty partnering with HCPs and connecting to an E-URD community. An overarching classification was developed to describe parental actions taken after an E-URD diagnosis: adjusting, managing, and pioneering. These classifications may help genetic counselors identify and facilitate positive steps with parents of a child with an E-URD.
    Keywords:  empowerment; genome and exome sequencing; parents; ultrarare genetic disorder
  4. Cell Death Dis. 2024 Apr 03. 15(4): 243
      The etiopathology of Parkinson's disease has been associated with mitochondrial defects at genetic, laboratory, epidemiological, and clinical levels. These converging lines of evidence suggest that mitochondrial defects are systemic and causative factors in the pathophysiology of PD, rather than being mere correlates. Understanding mitochondrial biology in PD at a granular level is therefore crucial from both basic science and translational perspectives. In a recent study, we investigated mitochondrial alterations in fibroblasts obtained from PD patients assessing mitochondrial function in relation to clinical measures. Our findings demonstrated that the magnitude of mitochondrial alterations parallels disease severity. In this study, we extend these investigations to blood cells and dopamine neurons derived from induced pluripotent stem cells reprogrammed from PD patients. To overcome the inherent metabolic heterogeneity of blood cells, we focused our analyses on metabolically homogeneous, accessible, and expandable erythroblasts. Our results confirm the presence of mitochondrial anomalies in erythroblasts and induced dopamine neurons. Consistent with our previous findings in fibroblasts, we observed that mitochondrial alterations are reversible, as evidenced by enhanced mitochondrial respiration when PD erythroblasts were cultured in a galactose medium that restricts glycolysis. This observation indicates that suppression of mitochondrial respiration may constitute a protective, adaptive response in PD pathogenesis. Notably, this effect was not observed in induced dopamine neurons, suggesting their distinct bioenergetic behavior. In summary, we provide additional evidence for the involvement of mitochondria in the disease process by demonstrating mitochondrial abnormalities in additional cell types relevant to PD. These findings contribute to our understanding of PD pathophysiology and may have implications for the development of novel biomarkers and therapeutic strategies.
  5. Pharmacoepidemiol Drug Saf. 2024 Apr;33(4): e5778
      PURPOSE: In rare diseases, real-world evidence (RWE) generation is often restricted due to small patient numbers and global geographic distribution. A federated data network (FDN) approach brings together multiple data sources harmonized for collaboration to increase the power of observational research. In this paper, we review how to increase reproducibility and transparency of RWE studies in rare diseases through disease-specific FDNs.METHOD: To be successful, a multiple stakeholder scientific FDN collaboration requires a strong governance model in place. In such a model, each database owner remains in full control regarding the use of and access to patient-level data and is responsible for data privacy, ethical, and legal compliance. Provided that all this is well documented and good database descriptions are in place, such a governance model results in increased transparency, while reproducibility is achieved through data curation and harmonization, and distributed analytical methods.
    RESULTS: Leveraging the OHDSI community set of methods and tools, two rare disease-specific FDNs are discussed in more detail. For multiple myeloma, HONEUR-the Haematology Outcomes Network in Europe-has built a strong community among the data partners dedicated to scientific exchange and research. To advance scientific knowledge in pulmonary hypertension (PH) an FDN, called PHederation, was established to form a partnership of research institutions with PH databases coming from diverse origins.
    Keywords:  common data model; federated data network; governance; rare disease; real‐world evidence; reproducibility; transparency