Intramyelin splitting in the spongiform lesions of Leigh syndrome.

A 5-month-old male infant, diagnosed as Leigh syndrome, presented with developmental delay, episodic apnea, metabolic acidosis, and myoclonic seizures. The magnetic resonance image of brain showed multiple symmetric low signals over the putamen in the T1-weighted axial view and linear high signal over the brainstem in the T2-weighted sagittal view. On electron microscopy, subsarcolemmal aggregation of abnormal mitochondria in muscle cells were found via biopsy. Small samples of myocardium, liver and brainstem, obtained via necropsy, were subjected to pathological examinations. On light microscopy, vacuoles were found in the myocardium and hepatocytes, while spongiform lesions in the neuropils, round cell infiltration, and vascular proliferation were observed in the brainstem. On electron microscopy, intramyelin splittings were observed in the spongiform lesions. We believe that intramyelin splitting must play an important role in the pathogenesis of spongiform lesions in Leigh syndrome.