- Little information is currently available on the outcome and the long-term restoration of immune function in infants with Omenn syndrome (OS) treated with bone marrow transplantation (BMT). We prospectively followed patients with OS who received matched unrelated donor (MUD) BMT at our center. Engraftment, immune reconstitution, and transplant-related complications were recorded. Humoral and cellular immunity were evaluated. Six patients with OS were diagnosed at a mean age of 4.6 months and received a matched unrelated donor BMT as the first BMT at the mean age of 9.4 months. All six patients are alive and well at a mean 95 months after transplant. All patients have evidence of full hemopoetic engraftment and robust immune function. We have shown here that matched unrelated donor BMT is highly effective in curing patients with OS regardless of their genotype. This mode of treatment should be preferred for patients with OS when a related identical donor is not available.