Spontaneous recovery of a childhood onset mitochondrial myopathy caused by a stop mutation in the mitochondrial cytochrome c oxidase III gene.

I n general, the clinical course of patients suffering from different types of mtDNA mediated neurodegenerative disorders progresses with age. The clinical progression of muscle weakness has been reported to correlate with an increase in cytochrome c oxidase (COX) negative fibres or with an increase of mutant mtDNA in skeletal muscle. In a recent issue we reported on a patient with mitochondrial myopathy with ragged red fibres (RRF), lactic acidosis, exercise intolerance, and delayed growth, with a heteroplasmic G9379A nonsense mutation (W58X) in the mtDNA encoded COIII subunit gene. A follow up examination of the patient showed significant improvement of the neurological symptoms. Here we present the results of detailed clinical, histological, immunohistological, biochemical, and genetic investigations of a repeated muscle biopsy, which all confirm a spontaneous regression of the disease.