Selective muscle MRI changes in a patient with a rare mitochondrial DNA variant causing myoclonic epilepsy with...

Area of Science:

• Genetics
• Mitochondrial Biology
• Neuromuscular Disorders

Background:

• Primary mitochondrial diseases are genetic disorders affecting oxidative phosphorylation due to nuclear or mitochondrial DNA mutations.
• These conditions can manifest with diverse clinical symptoms impacting multiple organ systems.

Observation:

• A young female patient presented with significant muscle weakness (myopathy) and acute heart failure.
• Lower limb MRI showed characteristic fatty infiltration and edema in specific muscles.
• Skeletal muscle biopsy revealed histopathological signs of mitochondrial dysfunction, including multiple respiratory chain deficiencies.

Findings:

• Whole mitochondrial genome sequencing identified a rare, likely pathogenic variant (m.8362T>G) in the MT-TK gene.
• This variant was present at high heteroplasmy levels.
• The variant was confirmed to be maternally inherited.

Implications:

• This case highlights the importance of considering mitochondrial genetics in patients with unexplained myopathy and cardiac issues.
• The identified MT-TK gene variant expands the spectrum of known mutations causing primary mitochondrial disease.
• Understanding the inheritance pattern is crucial for genetic counseling and family planning.