The hepatic mitochondrial DNA depletion syndrome: Ultrastructural changes in liver biopsies

Authors

  • Hanna Mandel,

    1. Metabolic Disease Unit, and B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
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  • Corina Hartman,

    1. Pediatric Gastroenterology Unit, Rambam Medical Center; the B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
    2. Electron Microscopy Unit, B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
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  • Drora Berkowitz,

    1. Pediatric Gastroenterology Unit, Rambam Medical Center; the B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
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  • Orli N. Elpeleg,

    1. Metabolic Disease Unit, Shaare Zedek Medical Center, Jerusalem; and
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  • Irena Manov,

    1. Electron Microscopy Unit, B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
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  • Theodore C. Iancu M.D.

    Corresponding author
    1. Electron Microscopy Unit, B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
    • Pediatric Research and Electron Microscopy Unit, B. Rappaport Faculty of Medicine, P.O.Box 9649, Haifa, 31096, Israel. fax: (972) 4-851-4285
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Abstract

Mitochondrial respiratory chain disorders are an established cause of liver failure in early childhood. In some patients, the levels of mitochondrial DNA are markedly reduced, a condition referred to as mtDNA depletion syndrome (MDS). We report here on the ultrastructural changes in the livers of 10 infants with the hepatic form of this syndrome. All patients displayed progressive liver failure, neurological abnormalities, hypoglycemia, and lactic acidosis that warranted investigation of respiratory chain disorder in liver tissue, specifically expressing the disease. Decreased activity of respiratory chain complexes containing mtDNA-encoded subunits (complexes I, III, IV) was shown in 5 patients. Mitochondrial DNA depletion was confirmed by Southern blot analysis in the livers of 6 patients. We found hepatocytes filled with mitochondria having aspects of “oncocytic transformation,” associated with numerous changes in shape, size, cristae, and matrix. The changes were virtually identical in all specimens. In many hepatocytes, microvesicular steatosis was the salient feature. Additional findings included cholestasis and focal cytoplasmic biliary necrosis (CBN), as well as cytosiderosis in hepatocytes and sinusoidal cells. In some hepatocytes the damage appeared extreme, but fibrosis was identified only in the few patients who died beyond 6 months of age. Although individual ultrastructural findings are not specific, when taken together, they show a diagnostic pattern highly suggestive of a respiratory chain disorder. In the appropriate clinical context, these findings can direct the clinician towards the diagnosis of hepatic MDS.

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