Possible role of thiamine in neuromuscular transmission

Complex mitochondrial disease caused by the mutation of COX10 in a toddler: a case-report study

Introduction and importance

Cytochrome C oxidase (COX) deficiency is an uncommon inherited metabolic disorder. It is identified by a lack of the COX, also known as Complex IV. This enzyme plays a crucial role in the rate-limiting and oxygen-accepting step of the respiratory chain within the subcellular structures called mitochondria. The deficiency of COX can either be restricted to skeletal muscle tissues or can impact multiple tissues throughout the body.

Case presentation

A 3-year-old girl was admitted due to muscle weakness and a decline in developmental milestones 7 days after a significant stressor. Leukodystrophy was observed in the brain magnetic resonance imaging, and genome sequencing identified a homozygous mutation in exon 1 and 7 of chromosome 17. This mutation led to a deficiency in COX10, which is a component of mitochondrial complex IV.

Clinical discussion

In the medical field, inherited metabolic disorders can be complex to diagnose due to overlapping symptoms with other conditions. Mitochondria's oxidative phosphorylation system, including the COX enzyme complex, plays a crucial role in energy production. Mitochondrial disorders, including COX deficiency, can present at various stages of life with diverse symptoms. Treatment options focus on supportive care and potential benefits from supplements like coenzyme-Q10 and small-molecule therapies targeting mitochondrial function. Identifying genetic mutations is key for advancing treatments in this area.

Conclusion

This report presents a unique case of developmental regression and muscle weakness in a paediatric patient, which can be attributed to a rare occurrence of type 3 nuclear mitochondrial complex IV deficiency.

Inheritance of physical fitness in 10-yr-old twins and their parents

This study focuses on the quantification of genetic and environmental sources of variation in physical fitness components in 105 10-yr-old twin pairs and their parents. Nine motor tests and six skinfold measures were administered. Motor tests can be divided into those that are performance-related: static strength, explosive strength, running speed, speed of limb movement, and balance; and those that are health-related: trunk strength, functional strength, maximum oxygen uptake, and flexibility. The significance and contribution of genetic and environmental factors to variation in physical fitness were tested with model fitting. Performance-related fitness characteristics were moderately to highly heritable. The heritability estimates were slightly higher for health-related fitness characteristics. For most variables a simple model including genetic and specific environmental factors fitted the observed phenotypic variance well. Common environmental factors explained a significant part of the variation in speed components and flexibility. Assortative mating was significant and positive for speed components, balance, trunk strength, and cardiorespiratory fitness, but negative for adiposity. Static strength, explosive strength, functional strength, and cardiorespiratory fitness showed evidence for reduced genetic transmission or dominance. The hypothesis that performance-related fitness characteristics are more determined by genetic factors than health-related fitness was not supported. At this prepubertal age, genetic factors have the predominant effect on fitness.