PSMA7 and metachromatic leukodystrophy: LV HSPC gene therapy has been successfully applied in clinical trials for the treatment of metabolic diseases, such as metachromatic leukodystrophy (MLD) [111], Fabry disease [112] and Hurler disease [113], as well as for peroxisomal disorder X-linked cerebral adrenoleukodystrophy (CALD), with reported follow-ups of 12 years after transplantation [114,115,116].