Phase III Trial of Coenzyme Q10 in Mitochondrial Disease

Inclusion Criteria: * Age 12 m - 17 y * Biochemical proof of a deficiency of complex I, III or IV of the RC or a molecular genetic proof of a mutation in mtDNA, or an nDNA mutation in a gene known to be associated with dysfunction of the electron transport chain (e.g., SURF1) * Willingness to stop all other medication regimens and supplements other than what the Steering and Planning Committee deems medically necessary Exclusion Criteria: * A genetic mitochondrial disease other than those stipulated under inclusion criteria * Intractable epilepsy, defined as grand mal seizures occurring with a frequency \> 4/month, despite treatment with conventional antiepileptic drugs * Primary, defined organic acidurias other than lactic acidosis (e.g., propionic aciduria * Primary disorders of amino acid metabolism * Primary disorders of fatty acid oxidation * Secondary lactic acidosis due to impaired oxygenation or circulation (e.g., due to severe cardiomyopathy or congenital heart defects) * Severe anemia, defined as a hematocrit \<30% * Malabsorption syndromes associated with D-lactic acidosis * Renal insufficiency, defined as (1) a requirement for chronic dialysis or (2) serum creatinine ≥ 1.2 mg/dl or creatinine clearance \<60 ml/min * Primary hepatic disease unrelated to mitochondrial disease * Allergy to CoQ10 or placebo ingredients * Pregnancy