Allogeneic Hematopoietic Stem Cell Transplantation Activity in Inborn Errors of Immunity in Russian Federation.

PURPOSE: Allogeneic hematopoietic stem cell transplantation (HSCT) is an established therapy for many inborn errors of immunity (IEI). The indications for HSCT have expanded over the last decade. The study aimed to collect and analyze the data on HSCT activity in IEI in Russia. METHODS: The data were collected from the Russian Primary Immunodeficiency Registry and complemented with information from five Russian pediatric transplant centers. Patients diagnosed with IEI by the age of 18 years and who received allogeneic HSCT by the end of 2020 were included. RESULTS: From 1997 to 2020, 454 patients with IEI received 514 allogeneic HSCT. The median number of HSCTs per year has risen from 3 in 1997-2009 to 60 in 2015-2020. The most common groups of IEI were immunodeficiency affecting cellular and humoral immunity (26%), combined immunodeficiency with associated/syndromic features (28%), phagocyte defects (21%), and diseases of immune dysregulation (17%). The distribution of IEI diagnosis has changed: before 2012, the majority (65%) had severe combined immunodeficiency (SCID) and hemophagocytic lymphohistiocytosis (HLH), and after 2012, only 24% had SCID and HLH. Of 513 HSCTs, 48.5% were performed from matched-unrelated, 36.5% from mismatched-related (MMRD), and 15% from matched-related donors. In 349 transplants T-cell depletion was used: 325 TCRαß/CD19+ depletion, 39 post-transplant cyclophosphamide, and 27 other. The proportion of MMRD has risen over the recent years. CONCLUSION: The practice of HSCT in IEI has been changing in Russia. Expanding indications to HSCT and SCID newborn screening implementation may necessitate additional transplant beds for IEI in Russia.