CD34 and metachromatic leukodystrophy: From 2019 to 2021, three gene therapies using genetically (lentiviral vector) modified autologous CD34+ hematopoietic stem cell transplantation were approved: Zynteglo for β-thalassemia [10], Skysona for adrenoleukodystrophy (ALD) [11, 12], and Libmeldy for metachromatic leukodystrophy (MLD) [13].