VPS11 and Pelizeaus-Merzbacher spectrum disorder: CSF cerebrospinal fluid, HMD hypomyelinating disease, LSD lysosomal storage disease, MR magnetic resonance, NCV nerve conduction velocity, NGS next generation sequencing, P3 3rd percentile, PMD Pelizaeus-Merzbacher disease, TLC thin layer chromatography, T2w T2-weighted image, V11D VPS11 deficiency