For the other 2 patients (1 with GAMT deficiency and 1 with SLC6A8 deficiency), DNA analysis was rejected by the parents and the diagnosis was confirmed by the absence of a creatine peak in brain 1H-MRS, the urinary profile and the deficiency of protein activities. This evidence concerns the gene SLC6A8 and hyperinsulinemic hypoglycemia, familial, 4.