Mitochondrial encephalomyopathies preceded by de-Toni-Debré-Fanconi syndrome or focal segmental glomerulosclerosis

We report two rare cases of mitochondrial encephalomyopathies which were preceded by renal diseases. One occurred in an 11-year-old girl diagnosed with Kearns-Sayre syndrome, which was preceded by de-Toni-Debré-Fanconi syndrome 8 years previously. The other occurred in a 14-year-old girl diagnosed with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes, who developed focal segmental glomerulosclerosis 3 years prior to confirmation of the diagnosis. Tissue from both patient demonstrated morphological abnormalities of the mitochondria in the distal renal tubular epithelium and leiomyocytes of the small renal artery. The present cases illustrate various clinical and morphologic evidence of renal diseases which may further our understanding of mitochondrial encephalomyopathies.