Any impairment in pyruvate oxidation, whether it be due to a deficit in mitochondrial pyruvate import as in our study, decreased PDH activity [29] or defects in the TCA cycle or the respiratory chain [31], would be expected to result in increased reduction of pyruvate to lactic acid by the LDH, greater release of lactic acid into the extracellular medium and consequently to metabolic acidosis. The gene discussed is PDP1; the disease is acidosis disorder.