Correction of neutropenia and hypogammaglobulinemia in X-linked hyper-IgM syndrome by allogeneic bone marrow transplantation

X-linked hyper-IgM (X-HIM) syndrome is a primary immunodeficiency disease c haracterized by defects in both cellular and humoral immunity. X-HIM is cau sed by mutations in the gene for CD40 ligand (CD40L), a T cell membrane pro tein that mediates T cell-dependent immune functions. We report the case of a 6-year-old male with X-HIM due to an intronic mutation resulting in aber rant CD40L RNA splicing and absence of detectable CD40L protein. The patien t had a history of multiple infectious complications and chronic neutropeni a requiring treatment with recombinant granulocyte colony-stimulating facto r, and underwent allogeneic bone marrow transplantation from an HLA-matched sibling donor. Following successful engraftment, T cell CD40L expression a nd immunoglobulin isotype switching were reconstituted and nentropenia reso lved. Allogeneic bone marrow transplantation can correct neutropenia and re constitute immune function in X-HIM.