On the other hand, it has to point out that often GLs and RCs not even exist for several treatable disorders, including different vitamin (thiamine, riboflavine, biotine, vitamin E)-responsive diseases, the glucose transporter type 1 (Glut1) deficiency, or the cerebrotendinous xanthomatosis (CXT), among others. Here, SLC2A1 is linked to cerebrotendinous xanthomatosis.