WHIM (warts-hypogammaglobulinemia-infections-myelokathexis) syndrome is an autosomal dominant primary immunodeficiency disorder caused by mutation of the CXC chemokine receptor 4 (CXCR4) gene (1, 2). Affected patients suffer from recurrent infections of the respiratory tract and soft tissues, and marked susceptibility to warts caused by human papilloma viruses from the second decade of life (3, 4). Granulocyte-macrophage colony stimulating factor (G-CSF) has been used to increase and maintain an adequate number of circulating neutrophils, and administration of intravenous immunoglobulin (IVIG) concentrates may help to decrease the number of infectious episodes caused by extracellular pathogens (5, 6). Nevertheless, the optimal therapy of patients with WHIM has not been clearly defined and patients continue to develop infections despite combination therapy with G-CSF and IVIG. None of the patients reported before has received hematopoietic stem cell transplantation (HSCT). We describe here a successful allogeneic HSCT in a girl with WHIM syndrome caused by c. 1013G> C sequence variant in the CXCR4 gene. Clinical and genetic details of this girl were described in the Journal before (2). IVIG infusions and varying doses of G-CSF were started at 6 and half years of age (2). She showed clinical improvement in the beginning but continued to develop respiratory infections leading to chronic obstructive pulmonary disease afterwards. At age 8 she was treated for a prolonged episode of dental periostitis complicated with purulent lymphadenitis. We counseled the family on the possibility of HSCT and umbilical cord blood (UCB) transplantation and the mother decided to become pregnant. She presented with a new pregnancy and at 11 weeks of gestation prenatal genetic testing revealed wild type CXCR4 sequences and HLA genotyping showed matching between the patient and the fetus (Fig. 1). Informed consent was obtained from the parents and the UCB transplantation was approved by the Hungarian National Transplant Committee. Umbilical cord blood stem cells were collected by standard methods