HPRT1 and hypoxanthine-guanine phosphoribosyltransferase deficiency: Although the switch from neuronal to glial gene expression might be expected to affect the generation or distribution of glial cells and altered myelination and ensheathment functions in HPRT deficiency, there have been until now no major neuronal or glial cyto-architectural aberrations described in HPRT-knockout mice and only occasional but unconfirmed demonstrations of glial or myelination disturbances with peripheral neuropathy in human LND patients [23], [24].