Of the 64 cases of primary lactic acidemias diagnosed (high lactic aciduria andlactic acidemia) detected on three consecutive occasions, only a few of them had thebiochemical and/or the molecular defect defined (including deficiencies ofglucose-6-phosphatase deficiency, fructose-1-6-biphosphatase, pyruvatedehydrogenase, and pyruvate carboxylase), indicating the difficulty of establishingthe biochemical cause in this group of disorders. This evidence concerns the gene PC and hyperinsulinemic hypoglycemia, familial, 4.