Indeed, effective long-term outcomes have been reported in a proportion of patients receiving human allogeneic or autologous CD34 and CD133 enriched HCTs [109,110,111] and, despite some significant challenges, in certain patients receiving autologous HCTs of ex vivo genetically engineered CD34+ HSPCs to treat such monogenic blood disorders as primary immunodeficiencies, hemoglobinopathies, BM failure syndromes, or inherited neurometabolic disorders (see recent reviews [112,113,114]). The gene discussed is CD34; the disease is inborn error of immunity.