Pyruvate kinase deficiency in 29 Turkish patients with two novel intronic variants.

Pyruvate kinase (PK) is a key enzyme of anaerobic glycolysis. The genetic heterogeneity of PK deficiency (PKD) is high, and over 400 unique variants have been identified. Twenty-nine patients who had been diagnosed as PKD genetically in seven distinct paediatric haematology departments were evaluated. Fifteen of 23 patients (65.2%) had low PK levels. The PK:hexokinase ratio had 100% sensitivity for PKD diagnosis, superior to PK enzyme assay. Two novel intronic variants (c.695-1G>A and c.694+43C>T) have been described. PKD should be suspected in patients with chronic non-spherocytic haemolytic anaemia, even if enzyme levels are falsely normal. Total PKLR gene sequencing is necessary for the characterization of patients with PKD and for genetic counselling.

Prognosis of Second Primary Malignancies in Pediatric Acute Lymphoblastic Leukemia Survivors: A Multicenter Study by the Turkish Pediatric Hematology Society.

The improved survival rates of childhood cancers raise the long-term risk of second primary malignancy (SPM) in childhood and adolescent cancer survivors. The intensity of the treatment protocol used, the use of some groups of chemotherapeutics, and radiotherapy were found to be risk factors for the development of second primary malignancies (SPMs). Forty-one patients who developed acute myelocytic leukemia or any solid organ cancer within 25 years of follow-up, after completion of pediatric acute lymphoblastic leukemia (ALL) treatment, were included in the study. The mean duration of initial ALL diagnosis to SPM was 9.3 ± 6.1 years. The 3 most common SPMs were acute myelocytic leukemia, glial tumors, and thyroid cancer. Thirteen (81%) of 16 patients exposed to cranial irradiation had cancer related to the radiation field. In total 13/41 (32%) patients died, and the 5-year overall survival rate was 70 ± 8%. Patients older than 5 years old at ALL diagnosis had significantly worse overall survival than cases younger than 5 years old. In conclusion, children and adolescents who survive ALL have an increased risk of developing SPM compared with healthy populations, and physicians following these patients should screen for SPMs at regular intervals.

Serum interleukin-33 and soluble suppression of tumorigenicity 2 in pediatric leukemia with febrile neutropenia.

The purpose of this study was to evaluate the association between interleukin-33 (IL-33) and its receptor Soluble Suppression of Tumorigenicity-2 (sST2) levels and bacterial infections during febrile neutropenia (FN) in pediatric patients with acute lymphoblastic leukemia (ALL). In this prospective, case-control study, participants were divided into 3 groups: ALL patients with FN (Group A), ALL patients without neutropenia and fever (Group B), and healthy children without infection and chronic disease (Group C). There were 30 cases in each group. Blood samples for IL-33 and sST2 have been drawn from patients in Group A before the initiation of treatment and on days 1 and 5 of treatment, and from patients in Groups B and C at initiation. At admission, mean IL-33 level (39.02 ± 26.40 ng/L) in Group B and mean sST2 level (185.3 ± 371.49 ng/ml) in Group A were significantly higher than the other groups (p = 0.038, p < 0.001, respectively). No difference was observed in the mean IL-33 and sST2 levels in the 5-day follow-up of patients in Group A (p = 0.82, p = 0.86, respectively). IL-33 and sST2 levels were not associated with fever duration, neutropenia duration or length of hospitalization. While C-reactive protein (CRP) was significantly higher in patients with positive blood culture (p = 0.021), IL-33 (p = 0.49) and sST2 (p = 0.21) levels were not associated with culture positivity.  Conclusion: IL-33 and sST2 levels were not found valuable as diagnostic and prognostic markers to predict bacterial sepsis in patients with FN. What is Known: • Neutropenic patients are at high risk of serious bacterial and viral infections, but the admission symptom is often only fever. • Febrile neutropenia has a high mortality rate if not treated effectively. What is New: • Febrile neutropenia is not only caused by bacterial infections. Therefore, new biomarkers should be identified to prevent overuse of antibiotics. • Specific biomarkers are needed to diagnose bacterial sepsis in the early phase of febrile neutropenia.

The Effects of Vitamin D on Myocardial Function Demonstrated by Speckle-Tracking Echocardiography in Children with Beta Thalassemia.

OBJECTIVE: Beta thalassemia major is an inherited hemoglobin disorder resulting in chronic hemolytic anemia. Cardiac involvement is the main cause of death in patients. Speckle-tracking echocardiography is a feasible method for the evaluation of cardiac function via an assessment of the longitudinal deformation of the myocardium through the cardiac cycle. The aim of our study is to evaluate the association between vitamin D deficiency and deformation of the left ventricular myocardium measured by speckle-tracking echocardiography in children with thalassemia major. METHODS: In this prospective study, 33 thalassemic patients with vitamin D deficiency were enrolled. Cardiac magnetic resonance T2* value, conventional echocardiography, and speckle tracking, and also left ventricular longitudinal and circumferential strain values were measured. Myocardial functions of the patients with vitamin D deficiency or insufficiency were evaluated by speckle-tracking echocardiography before and after vitamin D replacement. RESULTS: The mean age of the patients was 15.4 ± 3.09 years. Vitamin D level was deficient in 30 (90%) and insufficient in 3 (10%) of them. Speckle-tracking analysis showed a significantly decreased absolute value of the left ventricular global longitudinal strain before vitamin D replacement. A significant improvement in the global longitudinal strain was detected after vitamin D replacement (P < 0.05). A statistically significant increase was observed in parameters showing left ventricular systolic and diastolic functions after vitamin D replacement. CONCLUSION: Vitamin D deficiency is frequently observed and causes decreased contractility in thalassemic patients. In our study, we observed that our patients' cardiac functions had improved after vitamin D replacement therapy.

Does the use of infusion pumps increase hemolysis during blood transfusion in patients with thalassemia?

BACKGROUND: Patients with thalassemia need regular blood transfusions to maintain normal growth and suppression of ineffective erythropoiesis. Packed red blood cell (RBC) units can be delivered by infusion pumps (IPs); however, IPs may cause mechanical stress-induced RBC lysis. This study aimed to investigate the biomarkers of hemolysis related to transfusion techniques in patients with thalassemia. MATERIAL AND METHODS: Eighty-one thalassemia patients compared to those 42 healthy controls in terms of hemolysis markers (hemoglobin, plasma free hemoglobin (Hb), haptoglobin, potassium (K), lactate dehydrogenase (LDH)) before transfusion. Considering the age and peripheral venous diameter of the patient, the physician decided on the caliber of vascular access device (22 G or 24 G) for transfusion and the method to be used (gravitational method [GM] or IP). Hemolysis markers were repeated after transfusion in thalassemia patients. RESULTS: Packed RBC units were transfused to 24 (30 %) patients by IP and 57 (70 %) patients by GM. Plasma free Hb was significantly increased from 4.76 ± 7.92 mg/dL to 9.01 ± 7.66 mg/dL following transfusion (p < 0.001). There was no significant difference between IP and GM in terms of plasma free Hb increase. Post-transfusion plasma free Hb, LDH, and K levels significantly increased in patients who were transfused with 24 G catheters compared to those transfused with 22 G. CONCLUSION: An elevation in LDH levels was detected after transfusion with volumetric IPs; however, plasma free Hb or K levels were not affected by the transfusion method. Studies are needed to determine the factors associated with hemolysis after transfusion.

Pyruvate kinase deficiency mimicking congenital dyserythropoietic anemia type I.

BACKGROUND: Pyruvate kinase (PK) deficiency is the most common enzyme abnormality in the glycolytic pathway. Here, we describe two siblings with PK deficiency that mimicked congenital dyserythropoietic anemia (CDA) type I. CASE: The siblings were referred to our hospital for evaluation of anemia when they were newborns. Their PK enzyme activities were normal. Their bone marrow aspirations and electron microscopies showed CDA-like findings. A CDA panel with next-generation sequencing showed no mutation. Though their PK enzyme levels were normal, a molecular study of the PKLR gene showed a homozygous variant c.1623G > C (p.Lys541Asn) in exon 12 of our patients. CONCLUSIONS: Although the diagnosis of pyruvate kinase deficiency is difficult, it can be confused with many other diagnoses. Bone marrow findings of these cases are similar to congenital dyserythropoietic anemia. In patients with normal pyruvate kinase enzyme levels, the diagnosis cannot be excluded and genetic analysis is required.

Central Nervous System Fungal Infections in Children With Leukemia and Undergoing Hematopoietic Stem Cell Transplantation: A Retrospective Multicenter Study.

BACKGROUND: Central nervous system fungal infections (CNSFI) are seen in patients with hematologic malignancies and have high morbidity and mortality. Because of their rarity, there is limited data on CNSFI in children with no established treatment protocols or guidelines. MATERIALS AND METHODS: In this multicenter retrospective study, 51 pediatric patients with leukemia, 6 of whom had undergone bone marrow transplantation, with proven or probable CNSFI were evaluated. Fungal infections were defined as proven or probable based on European Organisation for Research and Treatment of Cancer criteria. Proven CNSFI was diagnosed by appropriate central nervous system (CNS) imaging or tissue sample findings in combination with positive microbiological results of cerebrospinal fluid. A positive culture, microscopic evidence of hyphae, a positive result of the galactomannan assays are defined as positive microbiological evidence. Probable CNSFI was defined as appropriate CNS imaging findings together with proven or probable invasive fungal infections at another focus without CNS when there is no other explanatory condition. Data was collected by using the questionnaire form (Supplemental Digital Content 1, http://links.lww.com/JPHO/A541 ). RESULTS: Seventeen patients had proven, 34 patients had probable CNSFI. Headaches and seizures were the most common clinical findings. The median time between the onset of fever and diagnosis was 5 days. The most common fungal agent identified was Aspergillus . Sixteen patients received single-agent, 35 received combination antifungal therapy. Surgery was performed in 23 patients. Twenty-two patients (43%) died, 29 of the CNSFI episodes recovered with a 20% neurological sequelae. CONCLUSION: CNSFIs should be considered in the differential diagnosis in patients with leukemia and refractory/recurrent fever, headache, neurologicalocular symptoms, and a radiologic-serological evaluation should be performed immediately. Early diagnosis and prompt management, both medical and surgical, are essential for improving clinical outcomes.

Evaluation of coagulation parameters and impact of transfusion on coagulation in patients with beta thalassemia major.

There have been several studies that have shown that patients with beta thalassemia major are at a higher risk of thrombosis due to the procoagulant activity of thalassemic erythrocytes, decreased liver synthetic function, increased platelet activity and vascular endothelial activation attributed to chronic oxidative stress, although there are no established tests to predict thrombotic risk in TM patients. In this study, we evaluated whether or not the platelet function analyser (PFA-200) and thrombin generation test (TGT) would be useful tools to identify hypercoagulability and risk of thrombosis in thalassemia major patients. The study included 50 patients with thalassemia major and 104 healthy control group. Pretransfusion and posttransfusion PFA-200 and TGT results were compared with control group. We found that median C/ADP and C/EPI values in the thalassemia major group were greater in both the pre and posttransfusion samples than the C/ADP and C/EPI results from the control group. The TGT results showed there was no difference between control group and the results from the thalassemia major group. The TGT and PFA-200 testing did not identify hypercoagulability nor identify clear testing parameters to predict a thalassemia major patient's risk of thrombosis. There may be other mechanisms/causes yet unidentified that could better explain thalassemia major patient's increased risk from thromboembolic events.

Analysis of fresh frozen plasma utilization indications in children: An audit of a tertiary care hospital in Turkey.

BACKGROUND: Although indications of fresh frozen plasma (FFP) usage are limited to certain circumstances in children, there is an increasing trend towards inappropriate usage are reported in clinical practice. The aim of this study was to evaluate the appropriateness of pediatric FFP utilization in our tertiary care hospital. METHODS: This prospective observational study was conducted at a tertiary care academic pediatric hospital. All FFP orders were evaluated for appropriateness over a 4-monts period by 2 hematologists. Data collected include demographic information, diagnosis, FFP transfusion indication, pre-transfusion coagulation tests, surgical procedure or bleeding status, and transfusion reactions. RESULTS: Three hundred twenty-four patients (57 % males, 43 % females) were transfused in 987 episodes. The mean age of the patients was 5.4±5.7 years. The majority of the patients (33 %) were under 1 y of age and the products were primarily utilized by pediatric and cardiovascular intensive care units. Pre-transfusion coagulation testing was only available in 674 (68 %) of the transfusion episodes. The rate of appropriate FFP transfusion episodes was 59 % (587/987). Inappropriate usage was mostly related to sepsis and minor coagulation abnormalities without bleeding. The higher rates of inappropriate transfusion orders were observed in pediatric and neonatal intensive care units, and hematology/oncology departments. CONCLUSIONS: Inappropriate use of FFP in children remains a significant challenge. The regular audit and sustainable education programs targeting the efficient use of FFP for health professionals at the national level can improve transfusion practices.

HEATR3 variants impair nuclear import of uL18 (RPL5) and drive Diamond-Blackfan anemia.

The congenital bone marrow failure syndrome Diamond-Blackfan anemia (DBA) is typically associated with variants in ribosomal protein (RP) genes impairing erythroid cell development. Here we report multiple individuals with biallelic HEATR3 variants exhibiting bone marrow failure, short stature, facial and acromelic dysmorphic features, and intellectual disability. These variants destabilize a protein whose yeast homolog is known to synchronize the nuclear import of RPs uL5 (RPL11) and uL18 (RPL5), which are both critical for producing ribosomal subunits and for stabilizing the p53 tumor suppressor when ribosome biogenesis is compromised. Expression of HEATR3 variants or repression of HEATR3 expression in primary cells, cell lines of various origins, and yeast models impairs growth, differentiation, pre-ribosomal RNA processing, and ribosomal subunit formation reminiscent of DBA models of large subunit RP gene variants. Consistent with a role of HEATR3 in RP import, HEATR3-depleted cells or patient-derived fibroblasts display reduced nuclear accumulation of uL18. Hematopoietic progenitor cells expressing HEATR3 variants or small-hairpin RNAs knocking down HEATR3 synthesis reveal abnormal acceleration of erythrocyte maturation coupled to severe proliferation defects that are independent of p53 activation. Our study uncovers a new pathophysiological mechanism leading to DBA driven by biallelic HEATR3 variants and the destabilization of a nuclear import protein important for ribosome biogenesis.

An outbreak of Ralstonia pickettii bloodstream infection among pediatric leukemia patients.

BACKGROUND: Ralstonia pickettii is an opportunistic waterborne microbe which can survive in many kinds of solutions. Contamination of these solutions may result as outbreaks, which can be mortal for immuncompromised patients. Herein we report an outbreak of R. pickettii related to contaminated saline infusion in our center. METHODS: This study was conducted in Ankara Pediatric City Hospital. An outbreak occured in Pediatric Hematology and Oncology Unit between August 28, 2019 and September 13, 2019. When the outbreak occured, infection control team began an investigation. Environmental samples were collected in order to find the source of the outbreak. RESULTS: A total of 11 patients with catheter related blood stream infection caused by R. pickettii who were diagnosed with leukemia were affected. None of the patients infected with R. pickettii died during the outbreak. A total of seventy environmental samples were cultured with the purpose of finding the source of outbreak. R. pickettii grew in normal saline solution culture and all isolates had the same clone of R. pickettii. The outbreak lasted two weeks and was controlled by stopping the usage and sending back the saline solutions belonging to the same manufacturing batch. CONCLUSIONS: We reported an outbreak of R. pickettii BSIs in highly immunocompromised patients due to contaminated intravascular solution, which was rapidly controlled by infection control measures. Vigilant surveillance by hospital infection control teams and prompt investigation to identify the source of nosocomial infections are crucial to stop an outbreak.

Hepatitis-Associated Aplastic Anemia: Etiology, Clinical Characteristics and Outcome.

Hepatitis-associated aplastic anemia (HAA) is a form of acquired aplastic anemia (AA) in which bone marrow failure develops after an acute attack of hepatitis. Bone marrow failure leading to AA is generally severe in cases of HAA and fatal if left untreated. This retrospective multicenter study investigated clinical and laboratory characteristics, possible causes, treatment, and outcome of HAA in children. Twenty patients from 8 centers were included in the study. Aspartate aminotransferase and alanine aminotransferase were <3 to 5×upper limit of normal (ULN) in 2 patients, <5 to 10×ULN in 2 patients, and >10×ULN in 16 patients. Acute liver failure developed in 5 (29%) patients. Pancytopenia was simultaneously present in 6 of 20 (30%) patients. Eleven of the 20 patients (55%) were alive, in remission and transfusion free. Those who were alive either had undergone hematopoietic stem cell transplantation and/or immunosuppressive treatment, except 1 patient who had received no treatment. Patients with the diagnosis of acute hepatitis should be evaluated and followed up carefully for presence of cytopenia, so that definitive treatment of AA can be initiated in a timely and appropriate manner when needed.

Evaluation of early-onset cardiotoxic effects of anthracyclines used during the treatment of childhood acute lymphoblastic leukemia by speckle-tracking echocardiography.

OBJECTIVE: Anthracyclines are widely used in the treatment of acute lymphoblastic leukemia (ALL). However, cardiotoxicity is the most critical side effect that requires dose limitation. It is thought to occur at first exposure, but the clinical presentation may occur years later. In this study, we aimed to determine the time of initial damage and cardiotoxicity that develops in children with ALL. METHODS: In this prospective study, 13 patients with newly diagnosed intermediate-risk precursor B cell ALL treated with the ALL-IC BFM 2009 protocol were included. Conventional echocardiography, tissue Doppler imaging (TDI), and speckle-tracking echocardiography (STE) were performed in all the patients before chemotherapy, after completing the induction phase, and at the end of the reinduction phase. RESULTS: The mean age of the patients was 7.8±4.6 (3.1-16.3) years. Myocardial velocity during systole (Sm) determined by TDI at the interventricular septum significantly decreased during the induction phase. Despite a decrease in STE parameters, a statistically significant reduction was determined in the global longitudinal strain rate at both left and right ventricles at the end of the induction. Nevertheless, a statistically significant increase was observed among the conventional echocardiographic findings in the left ventricular end-diastolic diameter at the end of the reinduction. CONCLUSION: During the treatment of ALL, subclinical anthracycline-associated cardiotoxicity develops in the early stages of treatment. The findings detected by TDI and STE could be missed by conventional echocardiography. We recommend evaluating patients with these newly developed techniques to detect subclinical cardiotoxicity at an early stage and starting appropriate therapy on time.

Pneumatosis cystoides intestinalis: A rare complication after hematopoietic stem cell transplantation.

BACKGROUND: Pneumatosis cystoides intestinalis (PCI) is a disorder in which widespread air sacs are present in mucosa, submucosa, subserosa, and intraabdominal area of the intestinal wall. It has a heterogeneous clinical presentation as a rare complication of intestinal graft-versus-host disease (GVHD). Computed tomography is the preferred imaging method for the diagnosis. Since the air sacs could be ruptured spontaneously, the presence of free air in the peritoneal cavity does not confirm intestinal perforation. The conservative treatment approach is sufficient in cases that do not require urgent surgical intervention, such as perforation or obstruction. CASE: Here, we present a 2.5-year-old patient diagnosed with primary hemophagocytic lymphohistiocytosis (pHLH), who underwent allogeneic hematopoietic stem cell transplantation from a matched unrelated donor (MUD) and developed PCI secondary to intestinal GVHD 14th months after HSCT. CONCLUSIONS: Pneumatosis cystoides intestinalis, which is a rare complication, should be kept in mind, especially in patients with intestinal GVHD and receiving intensive immunosuppressive, octreotide, and steroid treatment after HSCT.

Thrombolysis with Systemic Recombinant Tissue Plasminogen Activator in Children: A Multicenter Retrospective Study

Objective: This study aimed to evaluate systemic thrombolysis experiences with recombinant tissue plasminogen activator (rtPA). Materials and Methods: Retrospective data were collected from 13 Turkish pediatric hematology centers. The dose and duration of rtPA treatment, concomitant anticoagulant treatment, complete clot resolution (CCR), partial clot resolution (PCR), and bleeding complications were evaluated. Low-dose (LD) rtPA treatment was defined as 0.01-0.06 mg/kg/h and high-dose (HD) rtPA as 0.1-0.5 mg/kg/h. Results: Between 2005 and 2019, 55 thrombotic episodes of 54 pediatric patients with a median age of 5 years (range: 1 day to 17.75 years) were evaluated. These patients had intracardiac thrombosis (n=16), deep vein thrombosis (DVT) (n=15), non-stroke arterial thrombosis (n=14), pulmonary thromboembolism (PE) (n=6), and stroke (n=4). The duration from thrombus detection to rtPA initiation was a median of 12 h (range: 2-504 h) and it was significantly longer in cases of DVT and PE compared to stroke, non-stroke arterial thrombosis, and intracardiac thrombosis (p=0.024). In 63.6% of the episodes, heparin was initiated before rtPA treatment. LD and HD rtPA were administered in 22 and 33 of the episodes, respectively. Concomitant anticoagulation was used in 90% and 36% of the episodes with LD and HD rtPA, respectively (p=0.0001). Median total duration of LD and HD rtPA infusions was 30 h (range: 2-120 h) and 18 h (2-120 h), respectively (p=0.044). Non-fatal major and minor bleeding rates were 12.5% and 16.7% for LD and 3.2% and 25.8% for HD rtPA, respectively. At the end of the rtPA infusions, CCR and PCR were achieved in 32.7% and 49.0% of the episodes, respectively. The most successful site for thrombolysis was intracardiac thrombosis. HD versus LD rtPA administration was not correlated with CCR/PCR or bleeding (p>0.05). Conclusion: Systemic thrombolytic therapy may save lives and organs effectively if it is used at the right indications and the right times in children with high-risk thrombosis by experienced hematologists with close monitoring of recanalization and bleeding.

Loss of C2orf69 defines a fatal autoinflammatory syndrome in humans and zebrafish that evokes a glycogen-storage-associated mitochondriopathy.

Human C2orf69 is an evolutionarily conserved gene whose function is unknown. Here, we report eight unrelated families from which 20 children presented with a fatal syndrome consisting of severe autoinflammation and progredient leukoencephalopathy with recurrent seizures; 12 of these subjects, whose DNA was available, segregated homozygous loss-of-function C2orf69 variants. C2ORF69 bears homology to esterase enzymes, and orthologs can be found in most eukaryotic genomes, including that of unicellular phytoplankton. We found that endogenous C2ORF69 (1) is loosely bound to mitochondria, (2) affects mitochondrial membrane potential and oxidative respiration in cultured neurons, and (3) controls the levels of the glycogen branching enzyme 1 (GBE1) consistent with a glycogen-storage-associated mitochondriopathy. We show that CRISPR-Cas9-mediated inactivation of zebrafish C2orf69 results in lethality by 8 months of age due to spontaneous epileptic seizures, which is preceded by persistent brain inflammation. Collectively, our results delineate an autoinflammatory Mendelian disorder of C2orf69 deficiency that disrupts the development/homeostasis of the immune and central nervous systems.

Frequency and clinical characteristics of allergic transfusion reactions in children.

Allergic transfusion reactions (ATRs)are a common form of acute transfusion reaction. It was aimed to determine the clinical characteristics and frequency of ATRs in children. This study included children who were transfused with red cell concentrate (RCC), fresh-frozen plasma (FFP), platelet concentrates(PC), apheresis granulocyte, and cryoprecipitate.The patients' sociodemographic characteristics, the blood product that caused the reaction, the type and timing of the reaction, the patient's age at time of reaction and their diagnosis, follow-up period, and clinical data were recorded. A total of 89703 bags of blood products were transfused to 4193 children.Two hundred eleven acute transfusion-related reactions occurred in 157 (3.74%) patients.Of these, 125 reactions (59%) were allergic. ATR occurred in 125 of 89703 infusions (0.14%).The median age of patients was 9.99 years (IQR:4.67-14.38) and ATRs occurred at a median of 30 minutes into the transfusion. Eighteen (18%) of the patients also had a history of drug reaction.When the blood products that caused ATRs were examined, 43(34.5%) occurred with apheresis and single-donor PC, 37(29.6%) with FFP, 32 (25.6%) with RCC, 10(8%) with pooled PC, 2(1.6%) with cryoprecipitate, 1(0.8%) with apheresis granulocyte.Ninety-nine(79%) of the reactions were minor allergic reactions and 26(21%) were anaphylaxis.Compared to minor allergic reactions, the proportion of PCs was statistically higher in anaphylaxis(p=0.02). Patients receiving PC should be monitored more carefully during the first half hour of transfusion. In addition, approximately one-fifth of the patients who developed ATR also had a history of drug reaction. Patients with previous reactions to drugs may be more likely to have ATR.

Thrombin generation in children with febrile neutropenia.

BACKGROUND: Febrile neutropenia (FN) is a common and serious complication in patients with leukemia. Hemostasis and inflammation are two interrelated systems in response to infection. We aimed to investigate the course of thrombin formation in febrile neutropenia attack of children with acute lymphoblastic leukemia (ALL). METHODS: Thrombin generation was monitored in children treated for ALL at diagnosis of febrile neutropenia (FN) (t < sub > 0 < /sub > ), at 48 < sup > th < /sup > hour of FN (t1) and after recovery from neutropenia (t < sub > 2 < /sub > ). RESULTS: Twenty-nine patients and 50 healthy children as control were enrolled into the study. Mean endogenous thrombin potential (ETP) and mean peak value of thrombin results at t < sub > 1 < /sub > were significantly higher than at t < sub > 0 < /sub > , t < sub > 2 < /sub > and control groups, respectively. A positive but statistically nonsignificant correlation between ETP values at t < sub > 1 < /sub > and duration of neutropenia was observed. CONCLUSION: Although thrombin generation is enhanced both due to chemotherapy or malignancy itself, our results revealed that thrombin formation also increased in neutropenic infection of children with leukemia.