Pediatric Hematology/Oncology and Immunopathology

Introduction. Risk stratification in pediatric acute myeloid leukemia (AML) is traditionally based on the detection of chromosomal rearrangements using conventional molecular cytogenetic methods. However, these approaches are limited in detecting structurally complex and new genomic alterations. Whole-genome sequencing (WGS) overcomes these limitations, ensuring detection of all types of structural variants and providing their comprehensive molecular characterization.

Aim: to evaluate the capabilities of WGS in identifying chromosomal rearrangements in children with AML treated under the AML-MRD-2018 protocol.

Materials and methods. Out of 723 patients enrolled in the AML-MRD-2018 protocol, 335 (46%) children aged 0–18 years (median age – 9 years) were included in the study. WGS was performed on the DNBSEQ-T7 platform (150 × 2), with a median sequencing depth of 112×. Structural variants were identified using the MANTA algorithm with subsequent verification using a genome visualizer and confirmation by polymerase chain reaction and Sanger sequencing.

Results. The results of WGS and standard testing methods were completely concordant in 228 (68%) out of 335 patients. WGS identified key stratifying translocations: KMT2Ar (n = 137; 41%), RUNX1::RUNX1T1 (n = 34; 10%), CBFB::MYH11 (n = 27; 8%), NUP98r (n = 19; 6%). In patients in whom standard methods had failed to detect markers, WGS revealed 26 rearrangements, including cryptic variants of KMT2A (n = 7), NUP98 (n = 5) and ERG rearrangements (n = 2), as well as rare fusion genes. Three novel fusion genes were identified. Overall, WGS provided additional clinically significant information in 40 cases, with an added diagnostic yield of 12%.

Conclusion. WGS effectively detects both recurrent and rare, cryptic, and structurally complex chromosomal rearrangements, while providing their thorough molecular characterization. The method allows for improved risk stratification and can serve as a basis for minimal residual disease monitoring, increasing diagnostic accuracy and the potential for treatment personalization.

Introduction. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) using a TCRαβ/CD19 depletion platform is associated with a low incidence of graft-versus-host disease, however, delayed immune reconstitution increases the risk of opportunistic viral reactivation.

Aim: to analyze the kinetics of pathogen-specific immune reconstitution and its impact on clinical outcomes of allo-HSCT.

Materials and methods. We performed a retrospective analysis on a cohort of 265 children from the prospective database of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. All patients underwent their first allo-HSCT from a haploidentical donor with TCRαβ/CD19 depletion between September 2016 and March 2022. Pathogen-specific T-cell responses were assessed by IFN-γ ELISPOT assays (cutoff ≥10 SFC/3 × 10⁵ MNC) on days +30, +60, +90, +180, and at 1 year after allo-HSCT.

Results. For cytomegalovirus (CMV), the proportion of ELISPOT-positive patients increased from 38.5 to 70% during the first year after allo-HSCT. For adenovirus, the proportion of ELISPOT-positive patients was 7% on day +30, 16% on day +90, and 38–49% from day +180 to 1 year. For Epstein–Barr virus, the proportion of ELISPOT-positive patients reached 22% at 1 year after allo-HSCT. On day +30, SFC counts for CMV showed the strongest correlation with CD3⁺CD8⁺ T cells; by 1 year, this association was no longer evident (R² = 0.005; p = 0.058). CMV ELISPOT positivity on day +30 correlated with CMV reactivation (57% vs 42%; p = 0.012), reflecting the effect of antigenic stimulation on T cell expansion. On day +60, ELISPOT positivity predicted a more favorable course of viremia, including a shorter duration of viremia (4 weeks vs 6 weeks; p = 0.023) and a lower peak viral load (9587 copies/mL vs 23 525 copies/mL; p = 0.029). The cumulative risk of transplant-related mortality was 3% (95% confidence interval 2–6); the trend toward lower transplant-related mortality in patients with ELISPOT positivity on day +30 did not reach statistical significance (1% vs 4%; p = 0.798).

Conclusion. Therefore, reconstitution of pathogen-specific immunity after allo-HSCT is antigen-dependent. The presence of virus-specific T cells is associated with more effective control of viremia.

Introduction. Despite significant advances in the prevention and treatment of acute graft-versus-host disease (aGVHD) over the past decades, its severe forms remain one of the leading causes of mortality. Approaches to treating aGVHD and enteropathy are continually evolving. Presently, tumor necrosis factor inhibitors can be considered not only second- or third-line therapies but also first-line treatment.

Aim: to explore the use of adalimumab in children with intestinal aGVHD and enteropathy.

Materials and methods. This is the first Russian study on the use of adalimumab in children with intestinal aGVHD and enteropathy. From July 2025 to March 2026, the drug was administered to 5 children (4 boys and 1 girl): 3 of them with acute lymphoblastic leukemia, 1 with acute myeloid leukemia, and 1 with a congenital immune defect. The median age at the time of hematopoietic stem cell transplantation (HSCT) was 10 (4–16) years. Haploidentical HSCT was performed in 3 children, while the others underwent HSCT from HLA-matched unrelated donors. In 4 cases, native peripheral blood stem cells were used as the graft, and 1 patient received bone marrow-derived stem cells. For aGVHD prophylaxis/treatment, janus kinase inhibitors, cyclophosphamide, abatacept, rituximab, vedolizumab, tocilizumab, and etanercept were used. Adalimumab was indicated for enteropathy.

Results. Leukopoiesis recovery was achieved in all the patients within 15 (12–20) days, and complete donor chimerism has persisted since Day 30. In 3 out of 5 children, clinical response was observed after the first administration of adalimumab. One patient responded after the second administration: despite gastrointestinal contamination with Ps. aeruginosa and adenoviremia, escalation of immunosuppression did not affect resolution of the infection. In the patient with grade III–IV hepatic and intestinal aGVHD, a reduction to grade I was achieved after the 7^th adalimumab administration. All the children are currently alive, and four of them do not require inpatient treatment.

Discussion. Our findings suggest that adalimumab has great therapeutic potential. By specifically targeting the key proinflammatory cytokine, tumor necrosis factor-alpha, it can quickly and effectively relieve severe manifestations of intestinal syndrome in patients at high risk of post-transplant progression of enteropathy of various etiologies.

Conclusion. Adalimumab may be considered for the treatment of aGVHD and enteropathy but its use requires careful monitoring of infectious risks when integrated into combination immunosuppressive therapy.

Introduction. The rising incidence of mucormycosis among patients with hematologic and oncologic conditions has made it crucial to develop principles for the treatment of infectious complications as well as to assess the feasibility of allogeneic hematopoietic stem cell transplantation (HSCT) in this population.

Aim: to analyze the specific aspects and safety of HSCT in children with mucormycosis.

Materials and methods. This retrospective-prospective single-center study, conducted from 1 January 2013 to 31 March 2026 at the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology of Ministry of Healthcare of the Russian Federation, included HSCT recipients with a pre-transplant diagnosis of mucormycosis. The diagnostic work-up included computed tomography, magnetic resonance imaging, ultrasound, endoscopy, bronchoalveolar lavage, and biopsy of various organs and tissues depending on the site of involvement. From these specimens, slides were prepared in clearing solution supplemented with calcofluor white, a fluorescent agent. The slides were then examined under a fluorescence microscope using short-wavelength excitation at 400× magnification.

Results. We analyzed treatment outcomes in 13 patients (median age: 11.7 years), 77% of whom had hematologic malignancies. At mucormycosis onset, pulmonary involvement was observed in 62% of the patients, paranasal sinus involvement in 54%; liver, spleen, and central nervous system involvement in 8%, and disseminated disease in 31%. Etiologic confirmation (77%) revealed Lichtheimia corymbifera (n = 2), Rhizomucor pusillus (n = 2), Rhizopus oryzae (n = 2), Rhizopus microsporus (n = 1), Mucor indicus (n = 1), and Mucor spp. (n = 2). All the patients received targeted antifungal therapy (amphotericin B, posaconazole, isavuconazole), with combination treatment used in 77% of cases. Surgical treatment was performed in 92% of the cases. Notably, radical resection significantly reduced the need for repeat surgeries (p = 0.02). Allogeneic HSCT was mostly performed using ex vivo αβ T-cell depletion (n = 11). At the time of transplantation, active infection was observed in 5 patients, partial response in 5 and complete response in 3. The median time to engraftment was 12 (10–35) days. Glucocorticoids for graft-versus-host disease were required in 3 patients. Mucormycosis was cured in 100% of cases. The median time to complete response was 82 days with early partial response (<8 weeks) and 179 days with late response (p = 0.002). Infection status at HSCT did not affect the time to mucormycosis resolution. The overall survival was 59%, without any mucormycosis-associated deaths.

Conclusion. The use of modern HSCT technologies (such as αβ T-cell depletion) in combination with aggressive antifungal treatment enables successful transplantation even in children with active mucormycosis.

Introduction. Diamond–Blackfan anemia (DBA) is a rare congenital bone marrow failure syndrome classified as a ribosomopathy and characterized by selective aplasia of the erythroid lineage. Despite advances in understanding its pathogenesis, treatment options are still limited, and a significant proportion of patients remain transfusion-dependent.

Aim: to evaluate the effect of eltrombopag on the colony-forming potential of bone marrow erythroid progenitors in DBA patients in vitro.

Materials and methods. The study included 10 patients with genetically confirmed DBA and 7 healthy donors. Bone marrow mononuclear cells were cultured in a methylcellulose medium supplemented with eltrombopag at concentrations of 13 and 26 μg/mL.

Results. In vitro, the addition of eltrombopag to bone marrow cell cultures from the patients with DBA resulted in a significant increase in the number of erythroid colonies compared to control cultures without the drug. For early erythroid progenitors, a statistically significant increase in the number of colonies was observed.

Conclusion. These interim results suggest that eltrombopag may be considered a potential stimulator of erythropoiesis in DBA and support the need for further research in larger cohorts in order to clarify the clinical significance of the observed effects.

Aim: to evaluate changes in immunophenotype of leukemic blasts in acute lymphoblastic leukemia (ALL) relapse.

Materials and methods. The data of flow cytometric studies of paired diagnosis-relapse samples from 234 children with relapsed ALL were analyzed retrospectively.

Results. Among 212 B-lineage ALL cases, antigen expression changes in 21 (9.9%) patients led to a formal change of the immunophenotypic subtype of ALL. The most frequent direction of subtype change (43% of the cases) was intracellular IgM loss which resulted in a change from BIII to BII variant. Less frequently (in 38% of the cases) CD10 downexpression led to a change from BII to BI subtype. In T-lineage ALL patients, changes in the expression of antigens used for subtype classification were noted in 7 (31.8%) out of 22 cases. In six of them, tumor cells lacked CD1a which is crucial for the definition of TIII variant. The most frequent direction of subtype change was from TIII to TII, due to the loss of CD1a and absence of T-cell receptor expression.

Discussion. Relapses of ALL with subtype change did not differ from other relapses in either immunophenotypic stability, time to relapse or molecular characteristics of leukemic blasts. Such changes of subtype were mainly caused by the specifics of immunological classification and positivity thresholds. Therefore, immunophenotypic subtype shift is mainly formal and does not reflect significant changes in leukemia biology.

Conclusion. This immunophenotypical instability should be considered in order to avoid misinterpretation of flow cytometric data at relapse diagnosis. On the other hand, it shows the need for full immunophenotyping of tumor blasts also at relapse.

Introduction. Polycythemia vera (PV) is a Philadelphia chromosome (Ph)-negative myeloproliferative neoplasm that is extremely rare in childhood. Currently, there are no reliable data on the efficacy and tolerability of cytoreductive therapy in children with PV.

The aim of the study is to evaluate the clinical and hematological and molecular response, as well as the tolerability of cytoreductive therapy in patients under 18 years of age with PV.

Materials and methods. The Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology has developed its own management strategy for patients with PV: cytoreductive therapy is administered in the presence of a driver mutation in the JAK2V617F gene, JAK2 exon 12, and/or microcirculatory disorders with von Willebrand factor deficiency, or in the absence of an effect from antiplatelet agents in patients with microcirculatory disorders, or in patients with hemorrhagic syndrome and acquired von Willebrand factor deficiency. A total of 48 patients were included in the study (35 boys and 13 girls). The median follow-up period was 2.3 (2.0–3.7) years. The median age at diagnosis was 14.9 (9.0–16.8) years. The JAK2V617F mutation was found in 30 (62.5%) patients, the JAK2 exon 12 mutation – in 3 (6.25%) patients, and 15 (31.25%) patients were JAK2-negative. Cytoreductive therapy was administered to 28 (58%) patients.

Results. The majority of patients achieved a partial clinical and hematological response in the first year of treatment: 21/25 (84.0%) patients in the group treated with interferon and 7/8 (87.5%) in the group treated with hydroxycarbamide. In the interferon group, a partial molecular response was registered in 12/17 (70.5%) patients; 5/17 (29.5%) patients showed no molecular response. The median JAK2V617F/JAK2 exon 12 allele burden decreased from 24% (17–30%) to 15% (9–22%) (z = 3.5; p < 0.001). In the hydroxycarbamide group, the allele burden did not change significantly in any of the 7 (100%) patients (p = 0.916).

Conclusion. Our findings support further investigation of interferons as a preferred cytoreductive treatment option in children and adolescents with PV.

Introduction. Malignant neoplasms in children are recognized as one of the leading causes of childhood disability and mortality worldwide. Despite current advances in pediatric oncology, there is a high need, both in Russia and abroad, to optimize resources for the organization of medical care for children with cancer taking into account a multidisciplinary approach, standardization of patient referral procedures, implementation of resource-saving technologies, and personalized treatment strategies.

Aim: to evaluate the current organization of medical care for children with malignant neoplasms in the Stavropol Krai, identify its strengths and weaknesses, identify future directions for development, and propose ways to improve this system.

Materials and methods. We performed a retrospective analysis of epidemiological data (incidence, disability, and mortality rates) and resources of pediatric oncology and hematology service based on official statistical reports for 2015–2024 and materials from an on-site audit of the main regional healthcare facilities conducted in November 2024. We analyzed epidemiological trends in the Stavropol Krai over the past years and compared them with national data, and assessed organizational and methodological aspects of the service.

Results. In 2024, the incidence of cancer in children was 12.8 per 100 000 (76 new cases). Over 2021–2024, the trend was fluctuating, with a minimum of 10.8 per 100 000 in 2021 and a maximum of 14.2 per 100 000 in 2022. There is a steady increase in the number of new cases of cancer-related disability among children: from 31 cases in 2021 to 38 cases in 2024. Specialized care is centralized at the Regional Children’s Clinical Hospital and organized according to a three-tier system, with active referral of patients to federal centers. Times to diagnosis and treatment in case of acute leukemia are short (1–3 days and 1–2 days, respectively), in bone tumors – 5–7 days; however, there are still serious delays in the diagnosis and treatment of solid tumors (up to 10 days in case of lymphomas, 7–21 days in case of central nervous system tumors).

Conclusion. The strengths of the pediatric oncology/hematology service in the Stavropol Krai include the centralization of medical care, a well-developed regional health infrastructure, high staffing levels of pediatric hematologists, as well as prompt patient referral and timely treatment initiation for children with acute leukemia. However, there are still some issues to address, such as a shortage of pediatric oncologists and hematologist-oncologists, delays in the diagnosis and treatment of solid tumors, the need for further development of health infrastructure, standardization of patient referral pathways, and treatment outcome monitoring.

X-linked severe combined immunodeficiency (X-SCID) is an inborn error of immunity characterized by almost total absence of T and NK cells with normal counts of functionally impaired B cells (T^–B⁺NK^–) that is caused by pathogenic variants in the IL2RG gene resulting in early onset of life-threatening infections. Hypomorphic X-SCIDs present with variable clinical features and are characterized by later onset of infectious complications, a wide range of autoimmune manifestations, and increased risk of malignancies. In this article, we report a rare case of atypical X-SCID presenting with partial red cell aplasia and Burkitt leukemia as the first signs of immune dysregulation. Verification of the diagnosis of X-SCID leads to a different treatment approach, including the use of hematopoetic stem cell transplantation as a curative option. It highlights the importance of awareness of inborn errors of immunity among hematologists and oncologists.

Thiamine-responsive megaloblastic anemia (TRMA), also known as Rogers syndrome, is a rare autosomal recessive disorder first described by Dr. Lon E. Rogers et al. in 1969. This condition is defined by a classic triad of symptoms comprising megaloblastic anemia, diabetes mellitus and sensorineural hearing loss, although clinically it can still exhibit considerable phenotypic heterogeneity. The rarity of this disorder, with fewer than 200 affected individuals reported globally, coupled with its variable clinical manifestations, often leads to delayed or wrong diagnosis. TRMA is caused by mutations affecting the SLC19A2 gene which encodes the high-affinity thiamine transporter 1 essential for cellular thiamine uptake. While some manifestations of TRMA, particularly blood disorders and diabetes mellitus, respond well to high-dose thiamine supplementation, other symptoms such as sensorineural hearing loss remain irreversible.