Fludarabine-based Reduced Intensity Conditioning for Allogeneic Hematopoietic Stem Cell Transplantation in a Pediatric Patient With Bone Marrow Failure Syndrome Type 3.

Bone marrow failure syndrome (BMFS) type 3 is a rare genetic heterogeneous disorder, considered to be one of Inherited BMFSs related to ribosomopathies. It caused by a novel Homozygous variant in DNAJC21 gene, which affects cytoplasmic maturation of 60S ribosomal, leading to increase cell death, and inhibits cellular proliferation causing shwachman-diamond Syndrome-like syndrome. Only 15 cases of BMFS type 3 have been published in the literature. Therefore, the full phenotypic spectrum and the experience of hematopoietic stem cell transplantation (HSCT) are limited. Herein, we report an uncomplicated HSCT from human leukocyte antigen-identical sibling for a BMFS-3 patient at 22 months of age, who suffered from chronic diarrhea, severe failure to thrive and cytopenia required transfusions. We used a reduced intensity conditioning regimen including fludarabine, low-dose cyclophosphamide, and antithymocyte globulin with cyclosporine for prevent graft versus host disease. This regimen was safe and sufficient to achieve rapid engraftment without significant toxicity. Although, Mixed chimerism between 80% and 90% was observed since day +30, she gained 2 kg during 12 months post-transplant and no need for transfusions has been reported any more. Thus, we recommend HSCT with fludarabine-based reduced intensity conditioning regimen in this syndrome as progressive cytopenia occurs and an human leukocyte antigen-matched family donor is available.