Several factors for the establishment of MC have been identified, e.g., the underlying disease [inherited bone marrow failure syndromes (IBMFS) vs. hematologic malignancies, myeloid vs. lymphoid neoplasms)]; conditioning regimen [reduced-intensity conditioning (RIC) vs. myeloablative conditioning (MAC)]; use of T-cell depletion (TCD) (ex vivo, e.g., CD34+ selection; or in vivo, e.g., anti-thymocyte globulin (ATG) or alemtuzumab); and the dose of CD34+ cells infused (1–6). The gene discussed is CD34; the disease is hematologic disorder.