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Langerhans cell histiocytosis (LCH) is a disorder with a variety of clinical signs. The most severe forms affect risk organs (RO). The established role of the BRAF V600E mutation in LCH led to a targeted approach. However, targeted therapy cannot cure the disease, and cessation leads to quick relapses. Here, we combined cytosine-arabinoside (Ara-C) and 2'-chlorodeoxyadenosine (2-CdA) with targeted therapy to achieve stable remission. Nineteen children were enrolled in the study: 13 were RO-positive (RO+) and 6 RO-negative (RO-). Five patients received the therapy upfront, whereas the other 14 received it as a second or third line. The protocol starts with 28 days of vemurafenib (20 mg/kg), which is followed by 3 courses of Ara-C and 2-CdA (100 mg/m2 every 12 h, 6 mg/m2 per day, days 1-5) with concomitant vemurafenib therapy. After that, vemurafenib therapy was stopped, and 3 courses of mono 2-CdA followed. All patients rapidly responded to vemurafenib: the median disease activity score decreased from 13 to 2 points in the RO+ group and from 4.5 to 0 points in the RO- group on day 28. All patients except 1 received complete protocol treatment, and 15 of them did not have disease progression. The 2-year reactivation/progression-free survival (RFS) for RO+ was 76.9% with a median follow-up of 21 months and 83.3% with a median follow-up of 29 months for RO-. Overall survival is 100%. Importantly, 1 patient experienced secondary myelodysplastic syndrome after 14 months from vemurafenib cessation. Our study demonstrates that combined vemurafenib plus 2-CdA and Ara-C is effective in a cohort of children with LCH, and the toxicity is manageable. This trial is registered at www.clinicaltrials.gov as NCT03585686., (© 2023 by The American Society of Hematology. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

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 TCRαβ/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., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Objective: To assess risk factors (RF) and severity grade of Posterior reversible encephalopathy syndrome (PRES) in children with hematological diseases., Material and Methods: We analyzed cases of PRES in children during chemotherapy (CT) and after allogeneic hematopoietic stem cell transplantation (allo-HSCT). We estimated the following RF: arterial hypertension, steroid therapy, CT, immunosuppressive therapy (IST), infection and renal injury., Results: Thirty-five cases of PRES occurred in 32 patients (8 after allo-HSCT and 27 during CT) were included in this study. In the most of cases (94.3%), there were 2 and more RF. An increase in blood pressure level (88.6%), CT and IST (82.8%) administration, steroid therapy (71.4%) were the most significant for PRES development. Infectious process and the decline in renal function played a lesser role in this syndrome (31.4% and 14%). At the initial presentation of PRES, there were seizures (94.3%), a decrease of consciousness (28.6%), headache, vision disturbances and stomachache (20%). In the most of cases (91.4%), the 2 nd and 3d grade according to the Common Terminology Criteria for Adverse Events (CTCAE 5.0) were observed. Brain magnetic resonance imaging (MRI) revealed the vasogenic edema of temporal (88.6%), occipital (74.3%), frontal (40%) lobes and the cerebellum (22.9%) more often than the cytotoxic edema ( p =0.03). The cytotoxic edema was observed in the thalamus and the basal ganglia (2.9%) more often than in other parts of the brain ( p <0.01)., Conclusion: The majority of PRES cases are caused by more than two RF. Arterial hypertension does not have a leading role among its causes. There is a significant correlation between the grade of PRES according to CTCAE 5.0 score and RF number ( p <0.05).

We report incidence and deep molecular characteristics of lineage switch in 182 pediatric patients affected by B-cell precursor acute lymphoblastic leukemia (BCP-ALL), who were treated with blinatumomab. We documented six cases of lineage switch that occurred after or during blinatumomab exposure. Therefore, lineage conversion was found in 17.4% of all resistance cases (4/27) and 3.2% of relapses (2/63). Half of patients switched completely from BCP-ALL to CD19-negative acute myeloid leukemia, others retained CD19-positive B-blasts and acquired an additional CD19-negative blast population: myeloid or unclassifiable. Five patients had KMT2A gene rearrangements; one had TCF3::ZNF384 translocation. The presented cases showed consistency of gene rearrangements and fusion transcripts across initially diagnosed leukemia and lineage switch. In two of six patients, the clonal architecture assessed by IG/TR gene rearrangements was stable, while in others, loss of clones or gain of new clones was noted. KMT2A -r patients demonstrated very few additional mutations, while in the TCF3::ZNF384 case, lineage switch was accompanied by a large set of additional mutations. The immunophenotype of an existing leukemia sometimes changes via different mechanisms and with different additional molecular changes. Careful investigation of all BM compartments together with all molecular -minimal residual disease studies can lead to reliable identification of lineage switch.