A risk factor analysis of outcomes after unrelated cord blood transplantation for children with Wiskott-Aldrich syndrome

Abstract

Wiskott-Aldrich syndrome is a severe X-linked recessive immune deficiency disorder. A scoring system of Wiskott-Aldrich syndrome severity (0.5-5) distinguishes 2 phenotypes: X-linked thrombocytopenia and classic Wiskott-Aldrich syndrome. Hematopoietic cell transplantation is curative for Wiskott-Aldrich syndrome, however the use of unrelated umbilical cord blood transplantation has seldom been described. We analyzed umbilical cord blood transplantation outcomes for 90 patients. Median age at umbilical cord blood transplantation was 1.5 years. Patients were classified according to clinical scores (2 (23%), 3 (30%), 4 (23%) and 5 (19%)). Most patients received HLA mismatched umbilical cord blood transplantation and myeloablative conditioning with anti-thymocyte globulin. Cumulative incidence of neutrophil recovery at day-60 was 89% and day-100 acute graft-versus-host disease grade II-IV was 38%; use of methotrexate for graft-versus- host disease prophylaxis delayed engraftment (p=0.02), but decreased acute graft-versus-host disease (p=0.03). At 5-year, overall survival and event-free survival were 75% and 70%, respectively. Estimated 5 year- event-free survival was 83%, 73% and 55% for patients with clinical score 2, 4-5 and 3, respectively. In multivariate analysis, age<2years at umbilical cord blood transplantation and clinical phenotype X-linked thrombocytopenia were associated with improved event-free survival. Overall survival tended to be improved after 2007 (p=0.09). In conclusion, umbilical cord blood transplantation is a good alternative option for young children with Wiskott-Aldrich syndrome lacking an HLA identical stem cell donor