Bone marrow transplantation without conditioning regimen in Omenn syndrome: a case report.

OS is a non-SCID immunodeficiency characterized by a poor outcome even after BMT. We report here a case of BMT without preparative conditioning regimen, and with a successful engraftment in a five-month-old infant with OS. The patient was transplanted with 15 x 10(8) bone marrow mononuclear cells/kg, from his HLA matched brother, without preparative regimen and GVHD prophylaxis. Immunological status was assessed before and after the BMT, and the engraftment was monitored with microchimerism analysis. Six days after BMT, an acute GVHD involving first the skin, then the liver and gut, complicated the post-transplantation course. An excellent engraftment was confirmed by donor chimerism over 95% respectively at day post-transplantation 30, 60, 90, and 150. The cellular immunity of the patient was restored, and infectious complications decreased after BMT. Later the patient experienced chronic GVHD, and he died on day post-transplantation 246 from GVHD. BMT without conditioning regimen for OS is feasible, but there must be a megadose cell transplantation, and appropriate prophylactic immunosuppressive treatment to prevent acute GVHD.