Successful haploidentical PBSCT with subsequent T‐cell addbacks in a boy with HyperIgM syndrome presenting as severe congenital neutropenia

Jasinska A, Kalwak K, Trelinska J, Borowiec M, Piatosa B, Zeman K, Mlynarski W. Successful haploidentical PBSCT with subsequent T‐cell addbacks in a boy with HyperIgM syndrome presenting as severe congenital neutropenia. Abstract: HIGM syndrome is a group of primary immunodeficiency disorders characterized by recurrent bacterial and opportunistic infections; it is also associated with normal to elevated serum IgM levels and a concomitant deficiency of IgG, IgA, and IgE. In this report, we give account of a boy with X‐linked HIGM and a novel Y172C mutation within his CD40LG gene. He presented with severe neutropenia as the dominating symptom. His bone marrow showed maturation arrest at the promyelocyte/myelocyte stage, typical of congenital neutropenia. This boy suffered from life‐threatening infections and required high doses of rhG‐CSF, and a haploidentical PBSCT was also successfully performed, thus leading to reconstitution of CD40L expression on activated CD4+ T cells (as assessed with flow cytometry six months after the procedure). Two low‐dose T‐cell addbacks were required to re‐establish full donor chimerism and clear CMV reactivation. The report demonstrates that in select cases, alternative donor allogeneic HSCT supported by DLI may be effective in correcting the defect in X‐linked HIGM, and HSCT in HIGM children is not necessarily limited to matched sibling donor transplantation.