Molecular basis of infantile reversible cytochrome c oxidase deficiency myopathy

Area of Science:

• Genetics
• Mitochondrial Biology
• Pediatric Neurology

Background:

• Childhood mitochondrial encephalomyopathies are typically severe and progressive.
• A rare infantile form, 'benign cytochrome c oxidase deficiency myopathy,' shows spontaneous recovery, posing diagnostic challenges.

Purpose of the Study:

• To identify the molecular basis of benign infantile mitochondrial myopathy.
• To develop a genetic test for predicting prognosis in affected infants.

Main Methods:

• Genetic analysis of 17 patients from 12 families.
• Identification of a specific mitochondrial DNA mutation (m.14674T>C in mt-tRNA(Glu)).
• Functional studies to confirm mutation pathogenicity.

Main Results:

• A homoplasmic m.14674T>C mutation in the mitochondrial tRNA(Glu) gene was identified as the cause.
• This mutation was found in all tested patients with the benign form.
• Evidence suggests tissue-specific mechanisms contribute to spontaneous recovery.

Conclusions:

• The m.14674T>C mutation is the principal molecular cause of this benign mitochondrial myopathy.
• A simple genetic test can now differentiate infants with a good prognosis.
• This finding aids in clinical decision-making regarding intensive supportive care.