 - Children with a proven mitochondrial cytopathy documented on biopsies by histology, histoenzymology, ultrastructure and enzyme assay andor on body fluids by laboratory markers including lactacidemia, metabolic acidosis, increased CSF lactate, lactatepyruvate and beta-hydroxybutyrateacetoacetate ratios, paradoxical postprandial ketonemia, alaninemia, citrullinemia, plasma acylcarnitines. 