Pooled granulocyte concentrates (PGCs) prepared from whole blood donors without requiring pharmacological pretreatment represent an innovative approach that stands out with its donor safety, cost-effectiveness, and ease of clinical application. However, due to limited clinical data, it is open to further research. This retrospective study aimed to evaluate the effects of PG suspension applications on infection control and hematological parameters in pediatric hematology-oncology patients. Forty-nine pediatric patients who received PG suspensions at the Pediatric Hematology-Oncology and Bone Marrow Transplantation Centers of Erciyes University Faculty of Medicine between 2019 and 2024 were included in the study. The PGCs were transfused to patients according to clinical indications by pooling a certain number of residual leukocytes obtained from blood donors using a fully automated blood separation device (Reveos, Terumo). In a comparison of pre- and post-treatment hematologic parameters, statistically significant increases were found in white blood cell (WBC), hemoglobin (Hb), neutrophil count (NE), neutrophil percentage (NE%), monocytes (M), immature granulocytes (IG), and red blood cell count (RBC) (p < 0.05). No significant differences were found in C-Reactive Protein (CRP), platelet (PLT), or lymphocyte levels. Significant improvements were observed in hematologic parameters, particularly in the first two units, and the gradual decrease in CRP levels demonstrated that infection control was achieved. The findings suggest that PGCs obtained with the Reveos whole blood separation system and used as a pooled treatment may be an effective and safe supportive treatment option for infection control and hematologic improvement in severely neutropenic pediatric patients.

FLNA encodes filamin A, a ubiquitously expressed actin-binding cytoskeletal protein that cross-links actin filaments and links them to membrane-associated signaling complexes. Although FLNA has been implicated in T-cell signaling and regulatory T-cell development in murine models, its role in human immune-cell function remains incompletely understood. Here, we investigated the immunological phenotype associated with a novel hemizygous FLNA variant identified in a pediatric patient presenting with recurrent infections and inflammatory manifestations. Whole-exome sequencing revealed a hemizygous c.7405C>T (p.Pro2469Ser) variant in FLNA, which was confirmed by Sanger sequencing. Its potential impact on immune-cell function and cytoskeletal organization was evaluated using confocal microscopy, flow cytometry, and molecular assays. Patient-derived T cells showed impaired activation and proliferation following CD3/CD28 and IL-2 stimulation, accompanied by reduced CD25 and CD69 upregulation. CD4+ T cells also exhibited reduced IFN-γ, TNF-α, and IL-2 production after stimulation. Despite elevated basal phospho-STAT5 levels, IL-2-induced STAT5 phosphorylation and TCR-associated signaling responses, including pZAP70, pLCK, and p38 MAPK activation, were attenuated. Confocal imaging together with image-based quantification demonstrated altered cortical cytoskeletal organization in patient T cells despite preserved FLNA expression. In parallel, NK cells showed impaired activation responses and reduced cytotoxic activity under the assay conditions used. Increased apoptosis was observed in CD4⁺, CD8⁺, and NK-cell populations. Inflammatory cytokines were elevated in plasma and colonic tissue, whereas colonic ZO-1 and FLNA expression were reduced. Collectively, these findings indicate that the FLNA p.Pro2469Ser variant is associated with altered immune-cell signaling, disturbed cortical cytoskeletal organization, and immune dysregulation. This study expands the phenotypic spectrum linked to FLNA variants and supports a role for filamin A in human immune-cell regulation.

Pediatric immune thrombocytopenia (ITP) is an autoimmune cytopenia characterized by immune-mediated platelet destruction and impaired thrombopoiesis. Mucosa-associated invariant T (MAIT) cells are innate-like T cells activated by MR1-presented microbial metabolites and inflammatory cytokines, but their role in pediatric ITP and their relationship to eltrombopag therapy remain unclear. We analyzed peripheral blood mononuclear cells from healthy controls (n = 20), untreated pediatric ITP patients (n = 60), and eltrombopag-treated patients (n = 16). MAIT cells were quantified using MR1-5-OP-RU tetramers and surrogate gating (CD3+Vα7.2+CD161+). MAIT subsets, memory phenotype, chemokine receptor expression (CXCR3, CXCR5, CCR6), HLA-DR, intracellular cytokines (IFN-γ, TNF-α, IL-17 A, IL-22), and MR1+CD3- cells were analyzed by flow cytometry. Tetramer-defined MAIT cells were reduced in absolute number in pediatric ITP, including eltrombopag-treated patients, most prominently within the CD8+ subset, whereas their frequency among CD3+ T cells did not differ between untreated and eltrombopag-treated groups. In contrast, CD3+Vα7.2+CD161+ cells increased in untreated ITP and were lower in eltrombopag-treated patients. Untreated ITP patients exhibited reduced frequencies of IFN-γ- and TNF-α-producing MAIT cells, accompanied by increased IL-17-producing cells and TNF-α signal intensity. Conventional αβ T cells were reduced, whereas γδ T cells were increased; eltrombopag-treated patients exhibited γδ T-cell frequencies and cytokine-positive fractions closer to those of healthy controls. MR1+CD3- cells were expanded and displayed reduced HLA-DR expression in untreated ITP, whereas eltrombopag-treated patients showed lower MR1+CD3- frequencies and HLA-DR levels closer to healthy controls. These findings demonstrate coordinated alterations of the MAIT/MR1 axis and unconventional T-cell compartments in pediatric ITP and identify immunophenotypic differences associated with eltrombopag treatment.

Hemophilia, a congenital deficiency of factor VIII (hemophilia A) or factor IX (hemophilia B), leads to recurrent bleeding episodes that may cause progressive joint damage and long-term disability. Traditional management relies on intravenous factor replacement therapy; however, limited half-life, immunogenicity, venous access challenges, and the burden of frequent infusions have prompted the development of extended half-life (EHL) factor products. Although EHL therapies represent an important advancement, they only partially reduce treatment burden and do not fully meet expectations for improved convenience and sustained bleed protection. Recent innovations are reshaping the therapeutic landscape. Nonfactor subcutaneous therapies such as anti-TFPI molecules, antithrombin reducing agents, and anti-protein C agents offer simplified administration with the potential for improved adherence. Gene therapy provides the prospect of a long-term therapeutic effect in selected patients. In Türkiye, hemophilia care remains largely factor-based; however, clinical trial participation and recent regulatory approvals for selected novel therapies have begun to expand real-world experience with these emerging treatment options. As global practice shifts toward individualized, less invasive treatment approaches, expanding availability of novel therapies and optimizing patient-specific treatment strategies will be essential. This review examines current and evolving treatment options, key challenges, and future opportunities shaping the trajectory of hemophilia management.

Constitutional mismatch repair deficiency (CMMRD) is a rare cancer-predisposing syndrome. Recent studies have advanced our understanding of the genomic and epigenomic features of this disease, however, the mutational signatures and clonal evolution of CMMRD-associated high-grade gliomas (HGGs) requires further investigation. Herein, we analyzed the mutational signature and clonal evolution of 25 CMMRD-associated HGGs. Germline biallelic mutations in MSH6 (56.0%), PMS2 (36.0%), MLH1 (8.0%) were identified. Patients showed early onset (5.8 ± 4.2 years) and poor prognosis (progression-free survival 16 ± 18.0 months). Notably, we identified distinct mutational signatures, evolution pattern and clinical outcome between MSH6 and PMS2 subgroups, showing enriched SBS6 and SBSS21, respectively, which were found to correlate with prognosis. Clonal evolution model indicated early POLE/POLD1 events and survival of founding clone during tumor recurrence. These findings provide valuable insights into the genomic landscape and clinical outcomes of CMMRD-associated HGGs, emphasizing the critical role of mutational signature and tumor evolution in tumorigenesis and patient prognosis.

In this report, we identified a novel hemizygous ELF4 variant (c.1822G > C; p.Gly608Arg) in an adolescent male with chronic immune thrombocytopenia (ITP) and performed functional immunologic characterization. Peripheral blood mononuclear cells (PBMCs) of the patient and age-matched controls were characterized by flow cytometry with respect to T cell phenotype, activation, proliferation and NK cell cytotoxicity. The p.Gly608Arg substitution affects a highly conserved residue in the C-terminal regulatory domain of ELF4 and is predicted to be damaging. Immunophenotyping showed an expanded CD8+ T-cell compartment, an inverted CD4/CD8 ratio, reduced naïve T-cell populations, and accelerated acquisition of memory-like phenotypes upon activation. Both CD4+ and CD8+ T cells displayed increased proliferation following TCR stimulation, consistent with impaired ELF4-dependent regulation of effector T-cell expansion. NK cells exhibited reduced granzyme B and perforin expression and markedly diminished cytotoxicity against K562 targets, indicating defects in maturation and effector function. These findings suggest that the identified ELF4 variant is associated with combined T- and NK-cell dysfunction. This case expands the clinical spectrum of Deficiency in ELF4, X-linked and underscores the relevance of evaluating ELF4 mutations in patients with unexplained cytopenias accompanied by dysregulated lymphocyte activation and impaired cytotoxic responses.

BACKGROUND:Immune dysregulation plays a pivotal role in the pathogenesis of bronchiolitis. This study aimed to investigate the role of immune checkpoint molecules and regulatory cytokines in relation to disease severity. METHODS:A prospective cohort of 151 pediatric patients aged 1 month to 2 years was enrolled and classified into control, mild, moderate, and severe bronchiolitis groups. Immune checkpoint molecules (CTLA-4, TIM-3, TIGIT, GARP) and cytokines (IL-2Rα, 4-1BB, TGF-β1, LAG-3, galectin-9) were evaluated in CD4 + FOXP3+ (Treg) and CD4 + FOXP3-T cells, and in plasma using flow cytometry and ELISA. RESULTS:CD4+ T cell levels decreased with increasing disease severity. Treg frequencies were elevated in mild cases but decreased in moderate and severe cases. CTLA-4 and TIM-3 expression increased on both Treg and non-Treg CD4+ T cells in moderate and severe groups. Soluble PD-1, TIM-3, LAG-3, TGF-β1, and 4-1BB levels were significantly elevated in severe bronchiolitis. CONCLUSION:Disease severity in bronchiolitis is associated with immune checkpoint dysregulation and an immunosuppressive environment. The observed alterations in T cell subsets and increased expression of CTLA-4 and TIM-3 highlight the potential of these molecules as biomarkers of disease progression. IMPACT:This study demonstrates that the severity of pediatric bronchiolitis is associated with the dysregulation of immune checkpoint molecules. It adds novel insight into the immunopathogenesis of bronchiolitis by focusing on early immune biomarkers beyond conventional inflammatory parameters. These findings may support risk stratification and contribute to the development of targeted therapies in future pediatric bronchiolitis management.

TBK1 is a serine-tyrosine kinase protein that transmits signals from pattern recognition receptors to the NF-κB pathway leading to production of Type 1 Interferons. Mutations in this protein have been associated with arthritis, vasculitis, herpes simplex encephalitis and amyotrophic lateral sclerosis. In the current study, we characterized the functional consequences of a TBK1-variant bearing a truncation in exon 4 and 5 in a patient with poly arthritis resembling juvenile idiopathic arthritis and necrotizing encephalitis. The truncation was associated with reduced TBK1 protein abundance and altered phosphorylation. The variant was associated with increased basal/and or Poly-I: C induced IL-6, TNFα, IL-1β and IL-18 and type 1 Interferon ex vivo. Our findings expand the phenotypic spectrum of TBK1 loss-of-function variants and may provide insight into the management of immune dysregulation in affected patients.

Autoimmune hemolytic anemia is a rare immune-mediated disorder characterized by the destruction of red blood cells. Although the IFIH1 gene, which encodes melanoma differentiation-associated protein 5, has been implicated in various autoimmune and immunologic conditions, its involvement in AIHA has not been reported. We describe a 6-year-old boy with AIHA who carries a heterozygous IFIH1 c.2807+1G>A (rs35732034) variant. The patient showed a favorable response to corticosteroid therapy, maintaining remission on low-dose treatment. Functional studies demonstrate that this variant disrupts splice donor sites, resulting in marked impairment of MDA5 activity. This case suggests a possible genetic contribution of the IFIH1 variant to AIHA and highlights the importance of further investigation into its clinical relevance. Our findings expand current knowledge on IFIH1's role in immune regulation and its contribution to autoimmune pathogenesis.

10036 Background: Gene fusions involving NTRK1/2/3 represent actionable oncogenic drivers across a spectrum of rare pediatric solid tumors. Larotrectinib, a highly selective TRK inhibitor, has demonstrated robust efficacy and a favorable safety profile in clinical trials. However, real-world data from middle-income countries remain limited. We report a national multicenter real-world experience evaluating outcomes of pediatric patients with NTRK fusion–positive tumors treated with larotrectinib in Türkiye. Methods: This retrospective, descriptive multicenter study included pediatric patients (0–18 years) with histologically confirmed solid tumors harboring NTRK gene fusions, treated with larotrectinib for ≥1 month between August 2023 and April 2025. Clinical data were collected from 15 tertiary pediatric oncology centers. Treatment response was assessed using RECIST v1.1 or tumor-specific pediatric criteria. Adverse events were graded per CTCAE v5.0. Survival outcomes were analyzed descriptively. Results: Twenty-two patients were included; median age at diagnosis was 3 months (range, 1 day–182 months), and 59% were female. Infantile fibrosarcoma (IFS) was the most common diagnosis (n=16, 72.7%), followed by rhabdomyosarcoma (RMS), epithelioid sarcoma (ES), desmoplastic small round cell tumor (DSRCT). Six patients (27.3%) had metastatic disease at diagnosis. Larotrectinib was initiated due to disease progression or inadequate response to prior therapy in 86% of patients, treatment-related toxicity in 9%, and as maintenance therapy in one patient. After a median follow-up of 24 months, 10 patients achieved complete response, 6 had partial response or stable disease, and 4 experienced progression; 3 patients later relapsed. One patient died due to progressive disease. The 24-month overall survival rate was 95.5%, and 82% of patients remained event-free. No treatment-limiting adverse events were observed. Conclusions: In this national real-world cohort, larotrectinib demonstrated high efficacy, durable disease control, and an excellent safety profile in pediatric patients with NTRK fusion–positive solid tumors, particularly IFS. These findings support early integration of molecular diagnostics and TRK inhibition into routine pediatric oncology practice and provide valuable real-world evidence from a middle-income country setting. *Larotrectinib was provided through the early access to medicines program for humanitarian purposes and the data reflects real world data and does not reflect phase research data. The pharmaceutical company did not provide any kind of support in the planning/reporting/publication of the study.

Zeta-chain-associated protein kinase 70 (ZAP-70) deficiency, a rare form of combined immunodeficiency (CID), is caused by homozygous or compound heterozygous variants in the ZAP70 gene. ZAP-70, a tyrosine kinase, plays a key role in T-cell receptor (TCR) signaling, which is critical for T cell activation. ZAP-70 deficiency manifests clinically in a variety of ways, including recurring respiratory infections and cutaneous manifestations. This study describes the clinical, genetic, and immunological characteristics of four Turkish, two Syrian, and one Azerbaijani patient with ZAP-70 deficiency, including two novel variants. Among seven patients diagnosed with ZAP-70 deficiency, two previously unreported ZAP70 variants were identified. Functional analyses performed in four patients—including three with novel variants—demonstrated impaired TCR-induced proliferation, reduced Interleukin 2 (IL-2) production, and markedly diminished CD8⁺ T cell numbers, supporting the pathogenicity of these variants. Clinical phenotypes were heterogeneous, ranging from severe early-onset infections and cytopenias to autoimmune manifestations and atopy. Notably, even siblings carrying the same variant exhibited divergent immunological profiles and disease severity, highlighting the influence of potential genetic or environmental modifiers. Hematopoietic stem cell transplantation (HSCT) was curative in four patients, while one patient died before transplant. This report expands the genetic and phenotypic spectrum of ZAP-70 deficiency by describing two novel variants and emphasizing the value of functional analysis in variant classification and patient management.

BackgroundOsteopetrosis is a rare inherited disorder caused by impaired osteoclast number or function, leading to increased bone density, fractures, neurologic complications, and disturbances in calcium-phosphate homeostasis. This study aimed to describe the endocrine manifestations of childhood osteopetrosis, particularly osteopetrorickets, and to evaluate treatment responses and post-transplant calcium disorders.MethodsWe retrospectively reviewed 17 children diagnosed with osteopetrosis at a single tertiary center between 2015 and 2025. Clinical, biochemical, radiologic, genetic, and treatment data were analyzed.ResultsThe median age at diagnosis was 14 months (range, 15 days–130 months), and short stature was observed in 13 of 17 patients (76.4%). Ophthalmologic abnormalities were present in 10 patients (58.8%), hearing loss in 7 patients (41.1%), and hepatosplenomegaly in 7 patients (41.1%). TCIRG1 was the most frequent mutation, followed by CLCN7, TNFSF11, TNFRSF11A, and CA2. Osteopetrorickets was identified in 13 of 17 patients (76.4%); among these patients, hypocalcemia occurred in 11 of 13, hypophosphatemia in 8 of 13, and vitamin D deficiency in 4 of 13. Generalized osteosclerosis was observed in all patients, whereas classic osteopetrosis-associated radiographic findings, including bone-in-bone appearance, sandwich vertebrae, and Erlenmeyer flask deformity, were identified only in a subset of patients. Hematopoietic stem cell transplantation was performed in 11 of 13 patients with osteopetrorickets. Four of these 11 patients died during the early post-transplant period. Among patients with osteopetrorickets who underwent hematopoietic stem cell transplantation (HSCT) (n=11), seven surviving patients achieved complete resolution of rickets (7/11, 63.6%), allowing discontinuation of replacement therapy within 15 days to 8 months. Post-transplant hypercalcemia developed in 4 of 13 transplant recipients (30.8%).ConclusionsOsteopetrorickets is a frequent and clinically significant complication of pediatric osteopetrosis. Early recognition of mineral disturbances, genotype-based treatment planning, and close surveillance for rebound hypercalcemia after transplantation are essential to improve outcomes.

Marstacimab, a monoclonal antibody that inhibits tissue factor pathway inhibitor, is approved for prophylactic use in individuals with hemophilia A or B without inhibitors. We present efficacy and safety for individuals with inhibitors. The open-label, single-arm, phase 3 study evaluated once-weekly subcutaneous flat-dose marstacimab in males aged 12 to <75 years with severe hemophilia A or moderately severe to severe hemophilia B. Participants with inhibitors received bypassing agents (on-demand or routine prophylaxis) during a 6-month observational phase (OP) before entering a 12-month active treatment phase (ATP) with marstacimab. Primary end points were annualized bleeding rate (ABR) of treated bleeds and safety. Of 60 participants with inhibitors in the OP, 51 entered the ATP and received marstacimab. In the on-demand group (n = 48), mean estimated ABR declined from 19.78 (95% confidence interval [CI], 16.12-24.27) in the OP to 1.39 (95% CI, 0.85-2.29) during the ATP (ABR ratio, 0.07 [95% CI, 0.042-0.118]; 2-sided P< .0001). Results were consistent by hemophilia type (ABR ratio, 0.05 [hemophilia A, n = 40]; 0.13 [hemophilia B, n = 8]). Participants reported significant improvements in health-related quality of life. Adverse events were common but mostly mild; 1 treatment-related grade 3 skin rash led to discontinuation. Antidrug antibodies were detected in 19.6% of participants, with no apparent effect on efficacy or safety. In participants with inhibitors, marstacimab was associated with reduced bleeding rates and an acceptable safety profile, with no thromboembolic events. Marstacimab may be a viable treatment option for people with hemophilia A or B with inhibitors. This trial was registered at www.clinicaltrials.gov as #NCT03938792. ClinicalTrials.gov identifier: NCT03938792.

Aims: Infantile hemangioma (IH) is the most common benign vascular tumor in childhood. Diagnosis, treatment decisionmaking, and monitoring of the treatment are challenging. This study aims to investigate the utilization of platelet (PLT) indices as a marker in the follow-up of IH treatment. Methods: The patients who were admitted and followed up in the outpatient clinic of Erciyes University Department of Pediatric Hematology and Oncology were enrolled in the study. The demographical data, treatment results, and PLT indices of the patients at certain time points were analyzed retrospectively. PLT, mean platelet volume (MPV), and platelet distribution width (PDW) were measured at various time points: upon admission, after the first and second months of treatment, at treatment completion, and during rebound episodes in affected patients. Results: A general decrease in PLT, PDW, and MPV values was noted when comparing admission levels to the first month of treatment. The mean PLT count was 452.680/mm3 at admission, it decreased to 405.900/mm3 at the 1st month, 376.600/mm3 at the 2nd month and 359.900/mm3 at the end of treatment (p: 0,002). Besides MPV was evaluated, it was observed that while the mean was 10.43 fl at the time of admission, it decreased to 9.51 fl in the following months and the decline was statistically significant with a p value of 0,031. Lastly, regarding the mean PDW values, a decline was detected once again from 11.34 % to 10.2 % between the admission time and termination of the treatment with a statistically significant p value of