Immune cytopenia post-cord transplant in Hurler syndrome is a forme fruste of graft rejection

Abstract

Umbilical cord blood (UCB) is the preferred donor cell source for children with Hurler syndrome undergoing transplant, and its use has been associated with improved "engrafted survival" rates. However, as in other pediatric recipients of UCB transplants for nonmalignant disease, immune-mediated cytopenia (IMC) is a significant complication. This article describes 8 episodes of IMC in 36 patients with Hurler syndrome undergoing UCB transplant. The incidence of IMC was increased in those with a higher preconditioning absolute lymphocyte count and in those conditioned with fludarabine-containing regimens rather than cyclophosphamide, and it included red cell alloantibodies directed at cord blood group antigens that are novel to the recipient. In several cases, IMC was a precursor to immune-mediated complete graft rejection. We describe IMC as part of a spectrum of graft rejection by a residual competent host immune system and a forme fruste of complete graft rejection.

Conflict of interest statement

Conflict-of-interest disclosure: The authors declare no competing financial interests.

© 2019 by The American Society of Hematology.

Figures

Graphical abstract

Figure 1.

Risk factors for development of IMC. (A) Univariate analysis of risk factors for development of IMC after unrelated cord blood transplant for Hurler syndrome. Conditioning chemotherapy (FluBu) and preconditioning ALC were significant risk factors for the development of IMC. (B) Box and whisker plot comparing day 0 ALC of patients conditioned with busulfan and cyclophosphamide (BuCy) and FluBu (P = .001). (C) Box and whisker plot comparing preconditioning ALC of patients with and without an episode of IMC (P = .003). GvHD, graft-versus-host disease.