Pure myopathy associated with a novel mitochondrial tRNA gene mutation

Area of Science:

• Mitochondrial genetics
• Molecular biology
• Neuromuscular disorders

Background:

• Mitochondrial diseases are a heterogeneous group of disorders caused by mutations in mitochondrial or nuclear DNA.
• Mitochondrial myopathies are a common manifestation, often presenting with proximal muscle weakness and elevated creatine kinase.
• Identifying the genetic basis of these myopathies is crucial for diagnosis and understanding disease mechanisms.

Observation:

• A 47-year-old man presented with proximal muscle weakness, myalgia, and elevated creatine kinase, exhibiting a pure myopathic syndrome.
• Investigation revealed a novel mutation, a 5591G>A transition, in the mitochondrial tRNA(Ala) gene.
• This mutation was heteroplasmic and segregated with cytochrome c oxidase deficiency in muscle fibers.

Findings:

• The identified 5591G>A transition in the mitochondrial tRNA(Ala) gene meets established criteria for pathogenicity.
• The mutation is heteroplasmic, meaning it is present in a variable proportion of mitochondrial DNA molecules.
• Segregation analysis confirmed a link between the mutation and reduced activity of cytochrome c oxidase, a key enzyme in mitochondrial respiration.

Implications:

• This case highlights the significant clinical variability of mitochondrial diseases.
• The identification of this novel mutation expands the known genetic causes of mitochondrial myopathy.
• Understanding such mutations aids in the diagnosis and potential therapeutic strategies for mitochondrial disorders.