We report a 10-year-old boy with a severe form of immunodeficiency with hyp
er-IgM who underwent successful bone marrow transplantation with his HLA-ma
tched sister as donor. Busulfan (20 mg/kg) and cyclophosphamide (200 mg/kg)
were used as conditioning. The post-transplant course was uneventful. He i
s alive 25 months later with full hematological and immunological reconstit
ution.