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Benign reversible muscle cytochrome c oxidase deficiency: a second case
Insights
This case study highlights a benign infantile myopathy caused by reversible cytochrome c oxidase (COX) deficiency. Early symptoms improved, demonstrating the condition
Area of Science:
- Biochemistry
- Pediatric Neurology
- Mitochondrial Diseases
Background:
- Infantile myopathies can present with severe symptoms like generalized weakness and lactic acidosis.
- Cytochrome c oxidase (COX) deficiency is a known cause of mitochondrial myopathies.
Observation:
- A 6-week-old infant experienced generalized weakness, lactic acidosis, and required assisted ventilation.
- Muscle biopsies revealed mitochondrial, lipid, and glycogen accumulation with significantly reduced COX activity.
- Clinical improvement and resolution of lactic acidosis occurred by 6 months, with ventilation discontinued at 15 months.
Findings:
- Initial COX activity was 11% of control, increasing to 57% by 11 months, indicating reversible deficiency.
- Immunocytochemistry confirmed the presence of COX enzyme protein, despite low activity.
- Severe fibrosis noted in later biopsies may correlate with slower clinical recovery.
Implications:
- This case supports the existence of benign infantile myopathy linked to reversible COX deficiency.
- Understanding the reversibility of COX deficiency is crucial for diagnosing and managing pediatric mitochondrial disorders.
- Fibrosis progression may impact long-term prognosis in mitochondrial myopathies.
Abstract:
A 6-week-old boy had generalized weakness, requiring assisted ventilation, and lactic acidosis. At 6 months, the lactic acidosis resolved, and the patient started to improve; assisted ventilation was discontinued at 15 months. Muscle biopsies at 4 and 11 months showed accumulation of mitochondria, lipid, and glycogen; cytochrome c oxidase (COX) activity was 11% of the lowest control in the first biopsy and 57% in the second. Immunocytochemistry and immunotitration showed presence of immunologically reactive enzyme protein in both biopsies. This case confirms a previous report of benign infantile myopathy due to reversible COX deficiency. The severe fibrosis in the second biopsy may explain the slower rate of clinical recovery in this child.