Survival in primary hemophagocytic lymphohistiocytosis, 2016 to 2021: etoposide is better than its reputation.

ABSTRACT: Primary hemophagocytic lymphohistiocytosis (pHLH) is a life-threatening hyperinflammatory syndrome that develops mainly in patients with genetic disorders of lymphocyte cytotoxicity and X-linked lymphoproliferative syndromes. Previous studies with etoposide-based treatment followed by hematopoetic stem cell transplantation (HSCT) resulted in 5-year survival of 50% to 59%. Contemporary data are lacking. We evaluated 88 patients with pHLH documented in the international HLH registry from 2016-2021. In 12 of 88 patients, diagnosis was made without HLH activity, based on siblings or albinism. Major HLH-directed drugs (etoposide, antithymocyte globulin, alemtuzumab, emapalumab, ruxolitinib) were administered to 66 of 76 patients who were symptomatic (86% first-line etoposide); 16 of 57 patients treated with etoposide and 3 of 9 with other first-line treatment received salvage therapy. HSCT was performed in 75 patients; 7 patients died before HSCT. Three-year probability of survival (pSU) was 82% (confidence interval [CI], 72%-88%) for the entire cohort and 77% (CI, 64%-86%) for patients receiving first-line etoposide. Compared with the HLH-2004 study, both pre-HSCT and post-HSCT survival of patients receiving first-line etoposide improved, 83% to 91% and 70% to 88%. Differences to HLH-2004 included preferential use of reduced-toxicity conditioning and reduced time from diagnosis to HSCT (from 148 to 88 days). Three-year pSU was lower with haploidentical (4 of 9 patients [44%]) than with other donors (62 of 66 [94%]; P < .001). Importantly, early HSCT for patients who were asymptomatic resulted in 100% survival, emphasizing the potential benefit of newborn screening. This contemporary standard-of-care study of patients with pHLH reveals that first-line etoposide-based therapy is better than previously reported, providing a benchmark for novel treatment regimes.

Biallelic hypomorphic variants in CAD cause uridine-responsive macrocytic anaemia with elevated haemoglobin-A2.

Biallelic pathogenic variants in CAD, that encode the multienzymatic protein required for de-novo pyrimidine biosynthesis, cause early infantile epileptic encephalopathy-50. This rare disease, characterized by developmental delay, intractable seizures and anaemia, is amenable to treatment with uridine. We present a patient with macrocytic anaemia, elevated haemoglobin-A2 levels, anisocytosis, poikilocytosis and target cells in the blood smear, and mild developmental delay. A next-generation sequencing panel revealed biallelic variants in CAD. Functional studies did not support complete abrogation of protein function; however, the patient responded to uridine supplement. We conclude that biallelic hypomorphic CAD variants may cause a primarily haematological phenotype.

An improved index for diagnosis and mortality prediction in malignancy-associated hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening inflammatory syndrome that may complicate hematologic malignancies (HMs). The appropriateness of current criteria for diagnosing HLH in the context of HMs is unknown because they were developed for children with familial HLH (HLH-2004) or derived from adult patient cohorts in which HMs were underrepresented (HScore). Moreover, many features of these criteria may directly reflect the underlying HM rather than an abnormal inflammatory state. To improve and potentially simplify HLH diagnosis in patients with HMs, we studied an international cohort of 225 adult patients with various HMs both with and without HLH and for whom HLH-2004 criteria were available. Classification and regression tree and receiver-operating curve analyses were used to identify the most useful diagnostic and prognostic parameters and to optimize laboratory cutoff values. Combined elevation of soluble CD25 (>3900 U/mL) and ferritin (>1000 ng/mL) best identified HLH-2004-defining features (sensitivity, 84%; specificity, 81%). Moreover, this combination, which we term the optimized HLH inflammatory (OHI) index, was highly predictive of mortality (hazard ratio, 4.3; 95% confidence interval, 3.0-6.2) across diverse HMs. Furthermore, the OHI index identified a large group of patients with high mortality risk who were not defined as having HLH according to HLH-2004/HScore. Finally, the OHI index shows diagnostic and prognostic value when used for routine surveillance of patients with newly diagnosed HMs as well as those with clinically suspected HLH. Thus, we conclude that the OHI index identifies patients with HM and an inflammatory state associated with a high mortality risk and warrants further prospective validation.

Patient-tailored platelet transfusion practices for children supported by extracorporeal membrane oxygenation.

BACKGROUND AND OBJECTIVES: Extracorporeal membrane oxygenation (ECMO) serves as cardiopulmonary therapy in critically ill patients with respiratory/heart failure and often necessitates multiple blood product transfusions. The administration of platelet transfusions during ECMO is triggered by the presence or risk of significant bleeding. Most paediatric ECMO programmes follow guidelines that recommend a platelet transfusion threshold of 80-100 × 109/L. To reduce exposure to platelets, we developed a practice to dynamically lower the threshold to ~20 × 109/L. We describe our experience with patient-tailored platelet thresholds and related bleeding outcomes. MATERIALS AND METHODS: We retrospectively evaluated our platelet transfusion policy, bleeding complications and patient outcome in 229 ECMO-supported paediatric patients in our unit. RESULTS: We found that more than 97.4% of patients had a platelet count <100 × 109/L at some point during their ECMO course. Platelets were transfused only on 28.5% of ECMO days; and 19.2% of patients never required a platelet transfusion. The median lowest platelet count in children who had bleeding events was 25 × 109/L as compared to 33 × 109/L in children who did not bleed (p < 0.001). Our patients received fewer platelet transfusions and did not require more red blood cell transfusions, nor did they experience more haemorrhagic complications. CONCLUSION: We have shown that a restrictive, 'patient-tailored' rather than 'goal-directed' platelet transfusion policy is feasible and safe, which can greatly reduce the use of platelet products. Although there was a difference in the lowest platelet counts in children who bled versus those who did not, the median counts were much lower than current recommendations.

Genetic backgrounds and clinical characteristics of congenital neutropenias in Israel.

BACKGROUND: Congenital neutropenias are characterized by severe infections and a high risk of myeloid transformation; the causative genes vary across ethnicities. The Israeli population is characterized by an ethnically diverse population with a high rate of consanguinity. OBJECTIVE: To evaluate the clinical and genetic spectrum of congenital neutropenias in Israel. METHODS: We included individuals with congenital neutropenias listed in the Israeli Inherited Bone Marrow Failure Registry. Sanger sequencing was performed for ELANE or G6PC3, and patients with wild-type ELANE/G6PC3 were referred for next-generation sequencing. RESULTS: Sixty-five patients with neutropenia were included. Of 51 patients with severe congenital neutropenia, 34 were genetically diagnosed, most commonly with variants in ELANE (15 patients). Nine patients had biallelic variants in G6PC3, all of consanguineous Muslim Arab origin. Other genes involved were SRP54, JAGN1, TAZ, and SLC37A4. Seven patients had cyclic neutropenia, all with pathogenic variants in ELANE, and seven had Shwachman-Diamond syndrome caused by biallelic SBDS variants. Eight patients (12%) developed myeloid transformation, including six patients with an unknown underlying genetic cause. Nineteen (29%) patients underwent hematopoietic stem cell transplantation, mostly due to insufficient response to treatment with granulocyte-colony stimulating factor or due to myeloid transformation. CONCLUSIONS: The genetic spectrum of congenital neutropenias in Israel is characterized by a high prevalence of G6PC3 variants and an absence of HAX1 mutations. Similar to other registries, for 26% of the patients, a molecular diagnosis was not achieved. However, myeloid transformation was common in this group, emphasizing the need for close follow-up.

Excellent response to treatment with hydroxychloroquine in pediatric patients with SLE-related immune thrombocytopenia.

BACKGROUND: Pediatric immune thrombocytopenia (ITP) may precede systemic autoimmune disorders. In adolescent patients with ITP, routine screening for systemic lupus erythematosus (SLE) may be performed by testing for antinuclear antibody (ANA) titer. Hydroxychloroquine (HCQ) is a safe and effective immunomodulatory drug in patients with SLE but rarely used in ITP. We analyzed the platelet count response and safety of HCQ in treating pediatric patients with SLE-related ITP. METHODS: A retrospective study including pediatric patients with ITP and definite or incomplete SLE, who were treated with HCQ during 2010-2021. SLE was defined by ANA titer ≥ 1:160 as measured by immunofluorescence and ≥10 points according to the 2019 EULAR/ACR 2019 classification criteria, while patients with incomplete SLE achieved a score < 10. Complete response (CR) of the platelet count was defined as platelet count > 100 × 109/L; partial response (PR) as platelet count 30-100 × 109/L and exceeding ≥ twice baseline counts. RESULTS: Of the 17 patients included (median age 15.5 years; IQR 3.6), 15 (88.2%) were female, 13 had definite SLE, and four had incomplete SLE. HCQ was initiated at a median of 17 months after ITP diagnosis with a median platelet count of 38 × 109/L (IQR 28). At 8 weeks, 8 (47.1%) patients responded, including 6 (35.3%) achieving CR. After one year, the overall response was 82.4%, with the remaining patients having stable platelet counts requiring no additional ITP therapy. The response was maintained at a median follow-up of 42 months. No adverse effects to HCQ were noted. CONCLUSION: Pediatric patients with SLE-related ITP may benefit from treatment with HCQ.

A Need for a Novel Survival Risk Scoring System for Intensive Care Admissions Due to Sepsis in Pediatric Hematology/Oncology Patients.

Background: Children with hemato-oncological diseases or following stem cell transplantation (SCT) are at high risk for life-threatening infections; sepsis in this population constitutes a substantial proportion of pediatric intensive care unit (PICU) admissions. The current pediatric prognostic scoring tools to evaluate illness severity and mortality risk are designed for the general pediatric population and may not be adequate for this vulnerable subpopulation. Methods: Retrospective analysis was performed on all PICU admissions for sepsis in children with hemato-oncological diseases or post-SCT, in a single tertiary pediatric hospital between 2008 and 2021 (n = 233). We collected and analyzed demographic, clinical, and laboratory data and outcomes for all patients, and evaluated the accuracy of two major prognostic scoring tools, the Pediatric Logistic Organ Dysfunction-2 (PELOD-2) and the Pediatric Risk of Mortality III (PRISM III). Furthermore, we created a new risk-assessment model that contains additional parameters uniquely relevant to this population. Results: The survival rate for the cohort was 83%. The predictive accuracies of PELOD-2 and PRISM III, as determined by the area under the curve (AUC), were 83% and 78%, respectively. Nine new parameters were identified as clinically significant: age, SCT, viral infection, fungal infection, central venous line removal, vasoactive inotropic score, bilirubin level, C-reactive protein level, and prolonged neutropenia. Unique scoring systems were established by the integration of these new parameters into the algorithm; the new systems significantly improved their predictive accuracy to 91% (p = 0.01) and 89% (p < 0.001), respectively. Conclusions: The predictive accuracies (AUC) of the PELOD-2 and PRISM III scores are limited in children with hemato-oncological diseases admitted to PICU with sepsis. These results highlight the need to develop a risk-assessment tool adjusted to this special population. Such new scoring should represent their unique characteristics including their degree of immunosuppression and be validated in a large multi-center prospective study.

Atypical Presentations of Pediatric-acquired Thrombotic Thrombocytopenic Purpura.

BACKGROUND: Immune thrombotic thrombocytopenic purpura (iTTP) in children is a rare, severe thrombotic microangiopathy. This condition is characterized by microangiopathic hemolytic anemia, severe thrombocytopenia, and organ ischemia due to reduced activity of the von Willebrand factor-cleaving protease ADAMTS13. METHODS: A retrospective case series evaluating data collected from the medical files of 4 children diagnosed with iTTP. RESULTS: The presented case series depicts a variety of iTTP presentations: 1 case of primary iTTP, 1 case induced by Shiga toxin, 1 associated with RAS-associated autoimmune leukoproliferative disease (RALD), and 1 initial manifestation of systemic lupus erythematosus (SLE). Notably, 2 patients recovered without undergoing plasma exchange. CONCLUSION: Early ADAMTS13 testing in children with unexplained hemolysis or thrombocytopenia is crucial. The diverse underlying causes, including infections and autoimmune disorders, underscore the complexity of iTTP in the pediatric population. These cases highlight the necessity for personalized treatment approaches that consider each patient's unique clinical situation and potential alternatives or modifications to conventional therapeutic regimens.

Symptomatic corpus luteum hemorrhage in adolescent females with ITP.

Patients with immune thrombocytopenia (ITP) usually present with minor mucocutaneous bleeding. Corpus luteum hemorrhage (CLH) is generally asymptomatic but may, rarely, lead to severe intraperitoneal bleeding, mostly in patients with coagulation disorders. CLH causing intraperitoneal bleeding has only been described in few individuals with ITP. The objective of this retrospective observational study was to assess the clinical course and incidence of symptomatic CLH in adolescent females with newly diagnosed or chronic ITP. Additionally, a comprehensive literature review was conducted to scrutinize cases of pediatric female patients with ITP, complicated by CLH. We identified three patients with ITP and hemoperitoneum secondary to CLH. They presented with acute abdominal pain, had severe thrombocytopenia (platelet counts below 20 × 109/L), and required blood transfusions as well as ITP-directed therapy. All the patients were hemodynamically stable and did not require emergency surgical intervention.  Conclusion: CLH could potentially pose a significant complication in the context of adolescent females with ITP, requiring a strong index of suspicion to direct expedient therapy. What is Known: • Immune thrombocytopenia is typically associated with minor bleeding tendency. • Corpus luteum hemorrhage is generally asymptomatic; however, in women with bleeding disorders, it has the potential to result in substantial intra-abdominal bleeding. What is New: • Corpus luteum hemorrhage leading to intra-abdominal bleeding is a potential severe complication of immune thrombocytopenia in adolescent females.

Cellular and metabolic characteristics of pre-leukemic hematopoietic progenitors with GATA2 haploinsufficiency.

Mono-allelic germline disruptions of the transcription factor GATA2 result in a propensity for developing myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), affecting more than 85% of carriers. How a partial loss of GATA2 functionality enables leukemic transformation years later is unclear. This question has remained unsolved mainly due to the lack of informative models, as Gata2 heterozygote mice do not develop hematologic malignancies. Here we show that two different germline Gata2 mutations (TgErg/Gata2het and TgErg/Gata2L359V) accelerate AML in mice expressing the human hematopoietic stem cell regulator ERG. Analysis of Erg/Gata2het fetal liver and bone marrow-derived hematopoietic cells revealed a distinct pre-leukemic phenotype. This was characterized by enhanced transition from stem to progenitor state, increased proliferation, and a striking mitochondrial phenotype, consisting of highly expressed oxidative-phosphorylation-related gene sets, elevated oxygen consumption rates, and notably, markedly distorted mitochondrial morphology. Importantly, the same mitochondrial gene-expression signature was observed in human AML harboring GATA2 aberrations. Similar to the observations in mice, non-leukemic bone marrows from children with germline GATA2 mutation demonstrated marked mitochondrial abnormalities. Thus, we observed the tumor suppressive effects of GATA2 in two germline Gata2 genetic mouse models. As oncogenic mutations often accumulate with age, GATA2 deficiency-mediated priming of hematopoietic cells for oncogenic transformation may explain the earlier occurrence of MDS/AML in patients with GATA2 germline mutation. The mitochondrial phenotype is a potential therapeutic opportunity for the prevention of leukemic transformation in these patients.

Cytopenias in pediatric kidney transplant recipients: preceding factors and clinical consequences.

BACKGROUND: Kidney trans plantation is associated with secondary complications, including the risk of developing posttransplant cytopenias. This study aimed to evaluate the characteristics, identify predictors, and assess the management and consequences of cytopenias in the pediatric kidney transplant population. METHODS: This is a single-center retrospective analysis of 89 pediatric kidney transplant recipients. Possible factors preceding cytopenias were compared with the goal of recognizing predictors for posttransplant cytopenias. Posttransplant neutropenias were analyzed for the total study period and separately for the period beyond 6 months posttransplant (late neutropenias), to rule out confounding influences of induction and initial intensive therapy. RESULTS: Sixty patients (67%) developed at least one episode of posttransplant cytopenia. All episodes of posttransplant thrombocytopenias were mild or moderate. Posttransplant infections and graft rejection were found to be significant predictors for thrombocytopenia (HR 6.06, 95% CI 1.6-22.9, and HR 5.82, 95% CI 1.27-26.6, respectively). A total of 30% of posttransplant neutropenias were severe (ANC ≤ 500). Pretransplant dialysis and posttransplant infections were significant predictors for late neutropenias (HR 11.2, 95% CI 1.45-86.4, and HR 3.32, 95% CI 1.46-7.57, respectively). Graft rejection occurred in 10% of patients with cytopenia, all following neutropenia, within 3 months from cytopenia appearance. In all such cases, mycophenolate mofetil dosing had been held or reduced prior to rejection. CONCLUSIONS: Posttransplant infections are substantial contributors to developing posttransplant cytopenias. Preemptive transplantation appears to reduce risk of late neutropenia, the accompanying reduction in immunosuppressive therapy, and the ensuing risk of graft rejection. An alternative response to neutropenia, possibly using granulocyte colony stimulating factor, may diminish graft rejection. A higher resolution version of the Graphical abstract is available as Supplementary information.

Neonatal Thrombocytopenia: Differing Characteristics of NAIT Versus Non-NAIT.

While neonatal alloimmune thrombocytopenia (NAIT) is the most common cause of severe neonatal thrombocytopenia good clinical predictors are lacking. We analyzed cases of neonatal thrombocytopenia in Schneider Children's Medical Center of Israel to pinpoint qualifiers of NAIT (NAIT+) in comparison to non-NAIT (NAIT-) thrombocytopenia. Patient and maternal data were retrospectively collected on all thrombocytopenic newborns undergoing a workup for NAIT in our tertiary center between 2001 and 2016. Among 26 thrombocytopenic neonates, the mean nadir in NAIT+ patients (25×10 9 /L) was significantly lower than NAIT- patients (64×10 9 /L) ( P <0.001). 61.5% of NAIT+ infants required treatment compared with 23% of non-NAIT ( P =0.015). NAIT+ patients also required more therapeutic modalities than infants with NAIT- thrombocytopenia. Human platelet antigen (HPA)-1a and HPA-5b alloantibodies most frequently caused NAIT. In summary, thrombocytopenia in NAIT+ was significantly more severe compared with NAIT- and more likely to require treatment. In addition, despite the varied ethnic population in Israel, the HPA alloantibodies found in our population were most similar to those common in Western countries. In the absence of rigorous prenatal screening options, we suggest platelet counts below 40 to 50×10 9 /L in a healthy newborn be considered most suggestive for NAIT and warrant urgent NAIT-specific analysis.

Pediatric Mechanical Circulatory Support: Introduction and Schneider's Experience.

BACKGROUND: Ventricular assist devices (VADs) play a critical and increasing role in treating end-stage heart failure in pediatric patients. A growing number of patients are supported by VADs as a bridge to heart transplantation. Experience with VADs in the pediatric population is limited, and experience in Israel has not been published. OBJECTIVES: To describe this life-saving technology and our experience with VAD implantation in children with heart failure, including characteristics and outcomes. METHODS: We conducted a retrospective chart review of all patients who underwent VAD implantation at Schneider Children's Medical Center from 2018 to 2023. RESULTS: We analyzed results of 15 children who underwent VAD implantation. The youngest was 2.5 years old and weighed 11 kg at implantation. In eight patients, HeartMate 3, a continuous-flow device, was implanted. Seven patients received Berlin Heart, a pulsatile-flow device. Three children required biventricular support; 11 underwent heart transplants after a median duration of 169 days. Two patients died due to complications while awaiting a transplant; two were still on VAD support at the time of submission of this article. Successful VAD support was achieved in 86.6% of patients. In the last 5 years,79% of our heart transplant patients received VAD support prior to transplant. CONCLUSIONS: Circulatory assist devices are an excellent bridge to transplantation for pediatric patients reaching end-stage heart failure. VADs should be carefully selected, and implantation techniques tailored to patient's weight and diagnosis at a centralized pediatric cardiac transplantation center. Israeli healthcare providers should be cognizant of this therapeutic alternative.

[DEMOGRAPHIC, CLINICAL AND LABORATORY CHARACTERISTICS OF CHILDREN DIAGNOSED WITH HEMOPHAGOCYTIC LYMPHOHISTIOCYTOSIS (HLH) IN THE SCHNEIDER CHILDREN'S MEDICAL CENTER BETWEEN 2004-2020].

AIMS: To characterize the clinical, demographic, laboratory, and molecular biologic findings in children with HLH diagnosed and treated in our center. BACKGROUND: Hemophagocytic lymphohistiocytosis (HLH) is a rare immuno-hematologic disorder more common in children than adults. It is divided into two separate conditions which are not always easy to differentiate: familial/primary HLH (FHL) and acquired/secondary HLH associated with malignant, infectious, and other inflammatory conditions. FHL is a life-threatening disorder caused mainly by mutations in genes that code for proteins participating in perforin-dependent cell death. METHODS: We collected data from the records of all children who were diagnosed with HLH according to the accepted HLH criteria, and treated in the Schneider Children's Medical Center of Israel between the years 2004-2020. Demographic, clinical and laboratory data were summarized into a national database. RESULTS: A total of 36 children (18 boys,18 girls) who were diagnosed as having HLH according to the diagnostic criteria and received treatment according to the Histiocyte Society '94 or 2004 international protocols, entered the study. Eleven of the patients were Arab (30%), while 25 were Jewish (70%). The most frequent clinical signs were fever (89%) and hepatosplenomegaly (61%). Laboratory tests showed bipenia in 100% and increased levels of Interleukin-2 receptor (IL-2R) in 97%. Mutations in 3 out of the 4 common HLH genes were found in 15 (42%) children. The most common mutant gene was MUNC 13-4 comprising 40% of mutant genes. Mutations were quite common among Arab patients (81%) compared to the Jewish HLH population (20%) (p<0.001). Patients bi-allelic MUNC 13-4 mutations had a particularly poor prognosis with 66% succumbing to the disease. CONCLUSIONS: HLH is a severe, multisystem disorder. High clinical suspicion leading to timely diagnosis and treatment are crucial for preventing poor outcome and death. Genetic studies are of upmost importance in our population due to the high percentage of mutations, especially in the Arab population.

Syndromes predisposing to leukemia are a major cause of inherited cytopenias in children.

Prolonged cytopenias are a non-specific sign with a wide differential diagnosis. Among inherited disorders, cytopenias predisposing to leukemia require a timely and accurate diagnosis to ensure appropriate medical management, including adequate monitoring and stem cell transplantation prior to the development of leukemia. We aimed to define the types and prevalences of the genetic causes leading to persistent cytopenias in children. The study comprises children with persistent cytopenias, myelodysplastic syndrome, aplastic anemia, or suspected inherited bone marrow failure syndromes, who were referred for genetic evaluation from all pediatric hematology centers in Israel during 2016-2019. For variant detection, we used Sanger sequencing of commonly mutated genes and a custom-made targeted next-generation sequencing panel covering 226 genes known to be mutated in inherited cytopenias; the minority subsequently underwent whole exome sequencing. In total, 189 children with persistent cytopenias underwent a genetic evaluation. Pathogenic and likely pathogenic variants were identified in 59 patients (31.2%), including 47 with leukemia predisposing syndromes. Most of the latter (32, 68.1%) had inherited bone marrow failure syndromes, nine (19.1%) had inherited thrombocytopenia predisposing to leukemia, and three each (6.4%) had predisposition to myelodysplastic syndrome or congenital neutropenia. Twelve patients had cytopenias with no known leukemia predisposition, including nine children with inherited thrombocytopenia and three with congenital neutropenia. In summary, almost one third of 189 children referred with persistent cytopenias had an underlying inherited disorder; 79.7% of whom had a germline predisposition to leukemia. Precise diagnosis of children with cytopenias should direct follow-up and management programs and may positively impact disease outcome.

Rivaroxaban treatment among children with cancer-associated thromboembolism: Real-world data.

This is the first study examining real-life data of pediatric cancer patients treated with rivaroxaban. Children with thrombocytopenia and high bleeding risk were excluded from previous clinical trials. Data regarding the safety and efficacy of rivaroxaban in pediatric cancer-associated thrombosis are scarce. Our case series included 16 children aged 7.5-17 years. Thrombus resolution rate in our study was comparable to results of previous studies. However, higher rates of thrombotic and bleeding complications were seen in our study as compared to previous reports, especially among patients with relapsed or refractory disease.

Pediatric severe factor XI deficiency: A multicenter study.

BACKGROUND: Factor XI (FXI) deficiency is a rare autosomal recessive bleeding disorder. Only scarce publications address its clinical features in children. The increased prevalence of FXI deficiency in Israel enabled data collection for this large multicenter cohort study. OBJECTIVE: Some hemostatic challenges may be unique or more common in children, such as bleeding in the neonatal period or trauma-related injury. The current study was designed to explore the potential impact of these differences in children with severe FXI deficiency. METHODS: Medical files of all children with FXI level under 15% followed at five tertiary centers were evaluated. The retrieved data comprised demographic and clinical characteristics, including bleeding episodes, surgical interventions, treatment strategies, as well as laboratory features. RESULTS: Sixty children, whose median age at diagnosis was 4.2 years and their median FXI level was 4%, were included. Three children experienced triggered intracranial hemorrhage (ICH) and two children had major bleeds. No bleeding complications occurred in surgeries in which hemostatic treatment consisting mostly of tranexamic acid or fresh frozen plasma was applied (n = 45). In contrast, excessive bleeding was noted in 25% of surgical procedures performed without hemostatic preparation (p = .002). CONCLUSION: This study's findings confirm the generally favorable outcome of this rare bleeding disorder, with no spontaneous bleeds or cases of perinatal ICH. Nonetheless, proper diagnosis and adequate hemostasis in the surgical setting are imperative. Unlike previous studies in adults, our pediatric study suggests an association between the severity of FXI deficiency and bleeding tendency.

Congenital thrombocytopenia associated with a heterozygous variant in the MEIS1 gene encoding a transcription factor essential for megakaryopoiesis.

The transcription factor MEIS1 (myeloid ectotrophic insertion site 1) is crucial for the maintenance of hematopoietic stem cells and for megakaryopoiesis. Germline variants in MEIS1 are associated with restless-leg syndrome, but were not previously shown to cause cytopenias. This is the first report of a patient with congenital thrombocytopenia associated with a sequence variant in MEIS1, presenting with early onset severe thrombocytopenia and mild signs of bone marrow stress. Whole exome sequencing revealed a de novo monoallelic splice site variant in MEIS1, NM_002398.3:exon4:c.432 + 5 G > C, leading to a premature stop codon. We propose that heterozygous mutations in MEIS1 may cause congenital thrombocytopenia.

Incorporation of somatic panels for the detection of haematopoietic transformation in children and young adults with leukaemia predisposition syndromes and with acquired cytopenias.

Detection of somatic mutations may help verify the diagnosis of myelodysplastic syndrome (MDS) in patients with persistent cytopenias or with MDS-predisposition syndromes, prior to the development of overt leukemia. However, the spectrum and consequences of acquired changes in paediatric patients have not been fully evaluated, and especially not in the context of an underlying syndrome. We incorporated a targeted next-generation-sequencing panel of 54 genes for the detection of somatic mutations in paediatric and young adult patients with inherited or acquired cytopenias. Sixty-five patients were included in this study, of whom 17 (26%) had somatic mutations. We detected somatic mutations in 20% of individuals with inherited MDS-predisposition syndromes, including in patients with severe congenital neutropenia and Fanconi anaemia, and with germline mutations in SAMD9L. Thirty-eight per cent of children with acquired cytopenias and suspected MDS had somatic changes, most commonly in genes related to signal transduction and transcription. Molecularly abnormal clones often preceded cytogenetic changes. Thus, routine performance of somatic panels can establish the diagnosis of MDS and determine the optimal timing of haematopoietic stem cell transplantation, prior to the development of leukaemia. In addition, performing somatic panels in patients with inherited MDS-predisposition syndromes may reveal their unique spectrum of acquired mutations.

Mutations in RASGRP2 gene identified in patients misdiagnosed as Glanzmann thrombasthenia patients.

INTRODUCTION: Glanzmann thrombasthenia (GT) is a severe inherited platelet function disorder (IPFD), presenting with bleeding diathesis and impaired platelet aggregation, is caused by mutations in the genes ITGA2B or ITGB3. AIM: We aimed to study the genetic cause of IPFD mimicking GT. METHODS: During 2017-2019, 16 patients were referred to our tertiary center with bleeding symptoms, impaired platelet aggregation and normal platelet count and size. RESULTS: Using flow cytometry, 13/16 patients were diagnosed with GT, yet three patients displayed normal surface expression of the integrins αIIbß3 and αvß3, as well as normal integrin αIIbß3 activation following incubation with the activating monoclonal antibody anti-LIBS6, while platelet activation following ADP or epinephrine was impaired. Whole exome sequencing detected 2 variants in RASGRP2 gene in all 3 patients. DISCUSSION: Both RASGRP2 mutations predicted frameshift, premature stop codon (p. I427Mfs*92 and p. R494Afs*54, respectively) and truncated calcium-sensing guanine nucleotide exchange factor [CalDAG-GEFI]- the major signaling molecule that regulates integrin-mediated aggregation and granule secretion, causing IPFD-18. CONCLUSION: Patients who suffer from bleeding diathesis without immune dysregulation, may be mistakenly diagnosed as GT. Further studies are required to confirm the diagnosis of specific IPFD.