[P1-152] A Case of Reduced Mitochondrial Respiratory Chain Complex IV Activity with Serious Respiratory Disorder in Early Infancy
[Introduction] Mitochondrial diseases display various and nonspecific symptoms with slow or rapid progression, therefore a stepwise diagnostic approach would be rational to make a diagnosis of mitochondrial diseases, especially for the patients showing some suspicious symptoms in infancy. [Case] An infant was born at 38 weeks of gestational age without birth asphyxia. He developed inexplicable post-partum respiratory failure and required invasive mechanical ventilation for 7 days. Then he showed occasional myoclonus. ABR testing suggested the underlying sensory deafness. Since 4 months of age, apnea attacks and complex partial seizures appeared. The analysis of amino acid and acyl carnitine in blood, and urinary GC/MS demonstrated no abnormal findings. Levels of lactate and pyruvate in cerebrospinal fluid were not elevated. Developmental deterioration, such as losing eye-tracking, gradually appeared from 5 months of age. At 6 months, brain MRI detected high intensity area in bilateral subthalamic nuclei on T2WI, whereas MR spectroscopy showed no abnormal elevation of lactate in the brain. At 8 months of age, the histopathological examination of biceps muscle did not show the characteristic findings of mitochondrial diseases. Circumferential sequence analysis of mitochondrial DNA in lymphocytes showed no mutations. Finally, respiratory chain enzyme analysis of the muscle tissue demonstrated a reduced enzyme activity of complex IV (citrate synthase ratio 28.2%). [Conclusion] The non-specific but unusual symptom such as an inexplicable respiratory failure might be clue to reach diagnosis of mitochondrial disease. The laboratory or histopathological evaluation might miss the diagnosis, especially in infancy.