Allogeneic hematopoietic stem cell transplantation for seven children with X-linked hyper-IgM syndrome: a single center experience

X-linked hyper-IgM syndrome (XHIM), or hyper-IgM syndrome type 1 (HIGM1), is a rare primary immunodeficiency disorder susceptible to recurrent bacterial infection and opportunistic infection such as Pneumocystis carinii and Cryptosporidium parvum. The long-term outcome is quite poor, and allogeneic hematopoietic stem cell transplantation (HSCT) offers the only cure. Seven patients with XHIM, from age 3 to 19 years (mean 11.3 years), underwent allogeneic HSCT in our institution. Details of pre- and post-transplantation data and transplantation procedure were analyzed retrospectively. The donors were HLA-identical siblings for three patients and HLA-identical unrelated donors for four patients. All but one received conventional conditioning regimen consisting of busulfan and cyclophosphamide and prophylaxis for graft-versus-host disease (GVHD) consisting of cyclosporine and methotrexate. Five out of seven patients are alive and well with normal CD40L expression, and four of these five are free of intravenous immunoglobulin supplementation. The two patients who died had prolonged episodes of severe and recurrent infections and organ damage. We conclude that conventional allogeneic HSCT from HLA matched related or unrelated donors is curative and feasible for XHIM patients, if performed before significant infections and organ damage occur. For the high-risk patients, an alternative approach including nonmyeloablative HSCT may be more feasible.