Hematologic cancer developed in approximately 10% (7 of 67) of patients with cerebral adrenoleukodystrophy who received autologous hematopoietic stem-cell gene therapy with a lentiviral vector, predominant clones contained lentiviral vector insertions at multiple loci, including at either MECOM–EVI1 or PRDM16. The gene discussed is MECOM; the disease is hematopoietic and lymphoid cell neoplasm.