Background: Benign infantile cytochrome c oxidase deficiency myopathy is a mitochondrial disorder with reversible cytochrome c oxidase (COX) deficiency that presents in infants and is characteristic because spontaneous recovery can occur if affected in infants survive the first few months of life. This is because the enzyme defect in this condition is thought to be reversible. Recently, the m.14674T>C mt-tRNAGlu mutation has been associated with this condition.
Patient and methods: We report female patient who suffered muscle weakness as a newborn. She was admitted to hospital at the age of six months for investigation with a muscle biopsy. After two months she improved and was discharged. She remained well until the age of 34 years when she re-presented with symptoms of muscle weakness. She had a moderately elevated CK (308 U/L, normal <190) and EMG showed myopathic changes. A repeat muscle biopsy was performed.
Results: Her initial muscle biopsy showed numerous ragged red fibres with a variation of muscle fibre size (10-30mM in diameter). No COX staining was performed at the time of initial testing. Her repeat muscle biopsy showed sub-sarcolemmal mitochondrial accumulations and 2% COX negative fibres. Sequencing identified the homoplasmic mt-tRNAGlu mutation m.14674T>C.
Conclusions: We report the longitudinal course of a 34 year-old patient who had the clinical features, muscle biopsy changes and molecular analysis consistent with benign infantile COX deficiency myopathy in childhood. This patient illustrates that this condition, may not be entirely reversible and highlights the importance of providing patients with ongoing care beyond childhood.