SLC2A1 and Global developmental delay: In fact, IEMs as those linked to impaired glucose or pyruvate oxidation, such as mutations in glucose transporter 1 (GLUT-1), with reduced brain GLUT1 (G1D syndrome), mutations in pyruvate dehydrogenase (PDH) or in the mitochondrial pyruvate carrier (MPC deficiency) are currently associated with developmental delay, abnormalities of muscle tone, cerebral hypomyelination and hyperexcitability with refractory epileptogenic activity [102,103,104].