The common insertion sites detected in all six patients reflect the classic insertional pattern of lentiviral vectors, including PACS1 and KDM2A previously reported in metachromatic leukodystrophy,19 adrenoleukodystrophy, and β thalassemia20 gene therapy trials and not associated with clonal expansion. This evidence concerns the gene PACS1 and metachromatic leukodystrophy.