Treatment of tuberous sclerosis complex manifestations in children with mTOR inhibitors.

PURPOSE: Tuberous sclerosis complex (TSC) is a rare autosomal dominant genetic disorder that affects multiple organ systems. Mutations in the TSC1 and TSC2 genes result in the constitutive hyperactivation of the mammalian target of rapamycin (mTOR) pathway, contributing to the growth of benign tumors or hamartomas in various organs. Due to the implication of mTOR pathway dysregulation in the disease pathology, increasing evidence supports the use of mTOR inhibitors for treating multiple manifestations of TSC. METHODS: In this study, we conducted a retrospective analysis of clinical findings and treatment data from 38 patients diagnosed with tuberous sclerosis who were followed up in the Pediatric Oncology Clinic between 2010 and 2020. We collected information on patients' ages, genders, affected sites, familial history, imaging findings, presence of tumors, and treatments. RESULTS: Among the patients, nine individuals with TSC manifestations were treated with mTOR inhibitors. Specifically, everolimus was successfully administered to five patients with inborn cardiac rhabdomyoma causing hemodynamic impairment. In addition, two patients with refractory seizures received everolimus in combination with anti-epileptic drugs. A patient with renal angiomyolipomas larger than 3 cm was treated with everolimus, while a patient with extensive facial angiofibroma received topical sirolimus. All patients tolerated the mTOR inhibitors well, and the side effects were deemed acceptable. CONCLUSION: The utilization of mTOR inhibition in TSC is expected to become more prevalent in clinical practice, as current research is anticipated to provide a better understanding of the therapeutic roles of these treatments in TSC.

Neonatal Cardiac Rhabdomyoma: A Single-Center Experience.

AIM: Cardiac rhabdomyoma, known as the most common benign cardiac tumor in childhood, is strongly associated with tuberous sclerosis complex. This study aims to present our single-center experience regarding clinical observations, diagnostic approaches, and treatment modalities for cardiac rhabdomyoma identified during the neonatal period. PATIENTS AND METHODS: In this clinical observational study, we retrospectively assessed the outcomes of 12 newborn patients diagnosed with cardiac rhabdomyoma who were followed up in our neonatal intensive care unit over the past 12 years. RESULTS: The mean gestational age of the patients was 38.2±1.6 weeks, with an average birth weight of 3193±314 grams. The mean postnatal age at initial diagnosis was 12.42±15.75 days. Tuberous sclerosis complex was clinically identified in 50% of cases (six patients). Seven infants received everolimus treatment, while three infants underwent clinical monitoring without specific interventions. A significant reduction in cardiac mass size was observed in all surviving patients, leading to their subsequent discharge from the hospital. CONCLUSION: Cardiac rhabdomyomas often undergo spontaneous regression in early childhood. However, in cases with obstructive lesions or arrhythmias, they may present life-threatening consequences. Timely diagnosis, appropriate clinical management, and monitoring are crucial in optimizing outcomes for neonates with cardiac rhabdomyoma.

Evaluation of the Attitude of Parents in Pediatric Oncology Towards COVID-19 Vaccine.

Severe acute respiratory syndrome, coronavirus (SARS, COVID-19) has been declared a pandemic by the World Health Organization since March 2020. Patients with active cancer should be considered especially for priority access to the COVID-19 vaccine. Therefore, our study aimed to learn parents' opinions of cancer-diagnosed patients about the COVID-19 vaccine. Between December 2021 and January 2022, 76 people were willing to answer the questionnaire from the parents of outpatient/inpatient patients at the Pediatric Hematology and Oncology Clinic of Dr. Sami Ulus Obstetrics, Child Health and Diseases Education Research Hospital were included. In our study, 18 parents (23.7%) did not get vaccinated. Among the reasons for not getting vaccinated, the most common answer for "I fear from the vaccine's side effects.", "Do you think oncology patients are at risk for COVID-19?", "Do you think the COVID-19 pandemic affects cancer treatment?" were 90.7%, 89.5% and 21% yes, respectively. Would your opinion of the vaccine be positive if the domestic vaccine was produced?"-67.4% answered yes. Vaccine hesitation and public misinformation put cancer patients at risk. Increasing awareness of the rejection of COVID-19 vaccines is important for public health and the fight against the pandemic. In addition, the doctors' recommendations for conducting oncology treatment will significantly impact parents' compliance with the COVID-19 vaccine.

Dynamic Thiol-Disulfide Homeostasis in Children With ß-Thalassemia Trait.

In children with ß-thalassemia (ß-thal) trait, tissue damage occurs with oxidative stress due to oxygen free radicals and reactive oxygen species (ROS) production. Dynamic thiol-disulfide homeostasis (DTDH) is one of the most important indicators showing the pro-oxidant/antioxidant status in the body. In this study, we aimed to examine the status of DTDH by measuring native thiol, disulfide, and total thiol levels in children with ß-thal trait. The study included 40 children with ß-thal trait and 30 healthy controls (matched by age and gender). The DTDH parameters were measured by an automated method and results were compared between the groups. The levels of native thiol, total thiol, and disulfide in children with ß-thal trait group were statistically significantly higher than the control group (p < 0.001). There was no significant difference in disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol levels between the groups. In addition, there was no correlation between hemoglobin (Hb) and serum ferritin levels with the markers of DTDH in children with ß-thal trait. In our study, a significant increase was found in native thiol, total thiol, and disulfide levels in response to oxidative stress in children with ß-thal trait compared to the healthy control group. Disulfide levels of the children with ß-thal trait were higher than the control group, showing oxidative stress is high in ß-thal trait. Accordingly, it increases the native thiol and total thiol capacity as compensation.

Intrauterine Growth Retardation is a Risk Factor for Anthracycline Toxicity.

BACKGROUND: Anthracycline chemotherapy is used to treat a variety of cancers. However, late cardiac effects of anthracycline chemotherapy, such as subclinical left ventricular dilatation and/or dysfunction, have been observed in more than half of long-term survivors of childhood cancers. A major risk factor for anthracycline cardiotoxicity is intrauterine growth restriction (IUGR). We assessed the significance of IUGR as an important risk factor for late cardiotoxic effects of anthracycline therapy in asymptomatic long-term survivors of childhood cancers. MATERIALS AND METHODS: The study included 61 survivors of childhood cancers. Cardiac functions were prospectively studied using both conventional and non-conventional echocardiographic methods (two-dimensional speckle tracking echocardiography) after completion of the treatment. The patients were divided into two groups based on their birth weights: Group 1 (patients with IUGR) and Group 2 (patients with normal birth weight). RESULTS: Conventional echocardiography revealed a similar and normal range of left ventricle systolic and diastolic functions in both groups. However, global longitudinal and circumferential strain values demonstrated subclinical left ventricular systolic dysfunction in both groups as compared with normal reference strain values. Furthermore, Group 1 patients had significantly lower global longitudinal and circumferential strain and strain rate values than those in Group 2 patients. CONCLUSION: Asymptomatic long-term survivors of childhood cancers with a history of IUGR may have an increased risk of anthracycline cardiotoxicity due to the low content of mitochondrial DNA (mtDNA). IUGR is a risk factor for late anthracycline cardiotoxicity.

Cross-sectional study: long term follow-up care for pediatric cancer survivors in a developing country, Turkey: current status, challenges, and future perspectives

Aim: The main purpose of this study is to determine the current status of long-term follow-up (LTFU) for childhood cancer survivors and the challenges of LTFU for pediatric cancer survivors at pediatric oncology institutions in Turkey. Material and methods: A questionnaire was e-mailed to the directors of 33 pediatric oncology centers (POCs) registered in the Turkish Pediatric Oncology Group (TPOG). Of these 33 active TPOG institutions, 21 participated in the study and returned their completed questionnaires. Results: Only 1 of the 21 participating centers had a separate LTFU clinic. The remaining centers provided LTFU care for childhood cancer survivors at the pediatric oncology outpatient clinic. Of these centers, 17 (80.9%) reported difficulty in transition from the pediatric clinic to the adult clinic, 14 (66.6%) reported insufficient care providers, and 12 (57.1%) reported insufficient time and transportation problems. As neglected late effects, 16 (76.1%) centers reported psychosocial and getty job problems and 11 (52.3%) reported sexual and cognitive problems. None of the centers had their own LTFU guidelines for their daily LTFU practice Conclusion: This study was the first to gain an overview of the needs of POCs and the gaps in survivorship services in Turkey. The results from this study will help to develop a national health care system and national guidelines for pediatric cancer survivors.

Evaluation of long-term cardiac side effects of anthracycline chemotherapy by conventional and non-conventional echocardiographic methods in childhood cancer survivors.

OBJECTIVE: Anthracycline chemotherapeutic agents carry the well-recognised risk of cardiac toxicity. The aim of this study was to determine the long-term effect of anthracycline chemotherapy on the biventricular function in childhood cancer survivors using tissue Doppler imaging and two-dimensional speckle tracking echocardiography. PATIENTS AND METHODS: The study included 45 survivors of childhood cancers and 50 healthy age-matched control patients. Cardiac function was prospectively studied with conventional echocardiography, tissue Doppler imaging, and speckle tracking echocardiography after completion of treatment. The same analysis was performed on matched controls. RESULTS: There was no difference in age, gender, height, and weight between the study and control groups. The mean anthracycline dose was 240 ± 106 mg/m2 and the mean remission duration was 8.2 ± 5 years (1-20 years) in the study group. Conventional echocardiography showed similar ejection fraction, shortening fraction, and left ventricle end-diastolic diameter in both groups. Mitral lateral and septal tissue Doppler imaging showed normal but according to control group relatively sub-normal systolic and diastolic function in patient group. The global longitudinal and circumferential strain and strain rates were significantly lower in the patient group compared to control group. Correlation analysis revealed a negative and significant correlation between total anthracycline dose and global longitudinal and circumferential strain and strain rates. CONCLUSION: Sub-clinical systolic and diastolic dysfunction may not be detected by conventional echocardiographic methods which are frequently used in daily practice. Sub-clinical systolic and diastolic dysfunction may be detected more sensitively by echocardiographic method such as speckle tracking echocardiography in childhood cancer survivors.

Secondary hemophagocytic lymphohistiocytosis in pediatric patients: a single center experience and factors that influenced patient prognosis.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome of excessive immune activation. Secondary HLH syndrome develops as a complication of infection, drugs, rheumatologic conditions, or malignancy. The main objectives of this work were to identify the etiology of secondary HLH and prognostic factors associated with mortality. Patients diagnosed with secondary HLH, between January 2011 and December 2016, were retrospectively included in this study. We analyzed clinical and laboratory findings as well as prognostic factors from 24 pediatric patients diagnosed with secondary HLH. The mean age of patients at the time of diagnosis was 79.9 ± 68.7 months (range: 2-202) and 54.2% of the patients were male. The most frequent HLH-2004 criterion was fever (100%). Underlying triggers of HLH were as follows: 13 (54.1%) infections, juvenile idiopathic arthritis in 5 patients (20.8%), drugs in 3 patients (12.5%), malignancies in 2 (0.8%), Kawasaki disease in 1 (0.4%) patient, and 1 (0.4%) with unknown triggers. The median time of diagnosis was 3 days (1-67 days). Overall, the mortality rate was 20.8%. In our logistic regression model, factors associated with mortality were decreased albumin levels (OR1 = 2.3[1.48-3.43]) and etoposide usage (OR2 = 1.22 [1.14-1.89]). The patient's 30-day survival was inferior among patients whose albumin level was 2 g/dL or less compared to those over 2 g/dL. Increased awareness of the underlying condition is critical in HLH patients. Our study emphasizes the prognostic significance of albumin level.

Vitamin D Receptor (VDR) Polymorphisms in Pediatric Patients Presenting With Hodgkin's Lymphoma.

Vitamin D receptor (VDR) polymorphisms are found more commonly in some tumor types than in healthy individuals, suggesting that some polymorphisms (Cdx2, Fok1, Bsm1, Apa1, Taq1) contribute to tumor development. There is no previous report on VDR polymorphism in Hodgkin's lymphoma (HL) patients. VDR polymorphism patterns in 95 pediatric HL cases with 100 healthy controls were compared. No statistically significant difference was found between the patient group and control group in terms of Cdx2, Fok1, Bsm1, Apa1, and Taq1 polymorphisms (P>0.5). Our findings suggest that VDR polymorphisms may not play a role in HL development.

Vitamin D receptor polymorphisms in immune thrombocytopenic purpura.

BACKGROUND: Vitamin D receptor (VDR) polymorphisms have been studied in immune-mediated disorders, but not yet in immune thrombocytopenic purpura (ITP). We investigated whether VDR variants were associated with ITP in children. METHODS: The study included 44 children with a diagnosis of ITP and 100 healthy controls. Five VDR polymorphisms (Cdx-2, FokI, BsmI, ApaI and TaqI) were genotyped and used to evaluate the association of VDR variants with ITP. RESULTS: The distribution of the three Cdx-2 genotype groups (GG, GA, and AA) was significantly different between ITP patients and controls (P = 0.025); the homozygous GG genotype of Cdx-2 was overrepresented in ITP patients. The frequency of the A allele of Cdx-2 was significantly different between patients and controls (P = 0.01). The A allele of Cdx-2 was associated with a decreased risk of ITP (OR, 0.343; 95% CI: 0.150-0.782). No statistically significant difference was found between the ITP group and control group for Fok1, Bsm1, Apa1, and Taq1 polymorphisms (P > 0.5). CONCLUSION: There appears to be an interaction between the Cdx-2 variant of VDR and childhood immune thrombocytopenia.

How should we monitor boys with testicular microlithiasis?

Testicular microlithiasis (TM), a rare condition characterized by calcification within the seminiferous tubules, is associated with benign and malignant disorders of the testis. We review current practices of following up pediatric patients diagnosed TM incidentally on scrotal ultrasonography (US). We analyzed retrospectively patient characteristics, family history, indications for US, pathological features, US findings, outcome, and follow-up. At our institution, 2875 scrotal US examinations were performed on 2477 children with various scrotal complaints from 2008 to 2015. Testicular microlithiasis was detected in 81 patients (i.e., an incidence of 3.27%). Every 6 months, each patient underwent a clinical and ultrasonographic evaluation as well as serum tumor markers determination to detect a potential malignancy. Seventy-eight patients who had undergone scrotal US at least twice were included in this study. We evaluated the US studies for the type of TM (diffuse and focal) and change in follow-up studies. Testicular microlithiasis was typically diffuse (n = 56, 71.8%) and bilateral (n = 45, 57.7%), and it was detected the most frequently in the 9-11-year age group (27 patients, 34.6%). The most common comorbid conditions included undescended testes (31 patients, 39.7%) and hydrocele (11 patients, 14.1%). We found that serum tumor markers were within normal limits both at diagnosis and upon follow-up. No testicular tumors or new abnormal symptoms developed during the clinical follow-up. There is no convincing evidence that TM alone is premalignant in a pediatric population. In terms of follow-up, we advise regular self-examinations and annual US in the absence of risk factors.

Single-center experience with sirolimus therapy for vascular malformations.

Vascular malformations (VMs) are described as congenital malformations of the vasculature derived from capillaries, veins, lymphatic vessels, arteries, or a combination of these vessels. They can cause significant morbidity resulting from soft tissue hypertrophy-related disfiguration, bony abnormalities, and even organ compromise. They are usually treated with various interventional procedures to achieve local control; however, the chance of success decreases as the anatomical distribution of the malformation widens. Unfortunately, medical treatment options have been quite limited in these patients. Sirolimus is an antiangiogenetic and antiproliferative pharmacologic agent that has been used for the management of VM in the last decade. We report 6 pediatric patients (4 with capillary lymphaticovenous malformations, 1 with lymphaticovenous malformation, and 1 with venous malformation) seen at our clinic within the last 2 years with lesions covering wide anatomical areas. After the patients had unsuccessfully undergone various treatments at various centers, they were treated at our facility with peroral sirolimus. The mean duration of treatment was 13 months, but in 3 patients, tapered dosing continues. Five patients achieved partial responses. The response to sirolimus treatment increased as the lymphatic component of the VM increased. All patients tolerated sirolimus well; side effects were acceptable. Sirolimus is a safe and effective medical treatment for widely distributed VMs with significant lymphatic components and no further local treatment option.

Successful Treatment of Macroglossia Due to Lymphatic Malformation With Sirolimus.

OBJECTIVE: To evaluate the effectiveness and safety of sirolimus therapy in a child with macroglossia due to lymphatic malformation. METHODS: Sirolimus treatment was applied to the patient with an initial dosing of 0.8 mg/m2 per dose, administered orally, twice daily at approximately 12-hour intervals. RESULTS: After 9 months of sirolimus therapy, there was a nearly complete resolution of lymphatic malformation. The last evaluation was performed 6 months after withdrawal of treatment, and the lesion had almost completely resolved. CONCLUSION: This article presents a novel approach to the treatment of lymphatic malformation of the tongue using sirolimus, which appears to be safe and effective for the management of complex cases.

A subcutaneous paraspinal yolk sac tumor in a child.

A 3-year-old girl underwent a surgery at an external center on July 2011 for a swelling in the left lumbar paravertebral subcutaneous region. The mass was completely excised and the pathologic diagnosis was a yolk sac tumor (YST). Laboratory tests revealed a serum α-fetoprotein level of 278 IU/mL. Investigations using bone scintigraphy and magnetic resonance imaging revealed a scar tissue at the surgical site and lesions indicating metastasis at the lumbar first, second, third, and fifth vertebra. The patient was administered 5 cycles of PEB (cisplatin, etoposide, bleomycin) treatment. The serum α-fetoprotein was 3 IU/mL after the treatment. The lumbar magnetic resonance imaging and bone scintigraphy results were normal. The patient continues to be in remission since June 2012. YSTs are most commonly seen in the testis, ovary, and sacrococcygeal regions. Atypical locations have been reported with the primary lesion in the stomach, diaphragm, omentum, sino-nasal region, cranial base, lungs, vagina, and penis. Our case is probably a YST with an atypical location derived from preliminary cells left under the skin because of a migration defect.

A rare type of secondary cancer in a child with acute lymphoblastic leukemia: malignant fibrous histiocytoma.

Secondary cancers which are related with treatment of childhood acute lymphoblastic leukemia (ALL) is a significant problem with longer term. For development of secondary cancer after treatment, the latency period varies between 5 and 10 years. In this case, a 13 year-old-boy diagnosed as high-risk ALL was treated with chemotherapy and prophylactic cranial radiotherapy at a dose of 1800 cGy. Six years after the end of treatment he developed a 5 × 5 × 4 cm mass at the right temporal region of the cranium. The mass was excised totally with clear surgical margin. Pathology of mass has been diagnosed as malignant fibrous histiocytoma (MFH), recently referred to as an undifferentiated pleomorphic sarcoma (UPS). After treatment of childhood ALL, reported cases of secondary MFH is extremely rare in the literature. Herein we present a case of MFH/UPS that developed as a secondary cancer 6 years after the end of ALL treatment.

The relationship between cerebrospinal fluid osteopontin level and central nervous system involvement in childhood acute leukemia.

The aim of this study was to evaluate the relationship between cerebrospinal fluid (CSF) osteopontin (OPN) levels and central nervous system (CNS) involvement in children with a diagnosis of acute leukemia. The study sample consisted of 62 patients who had been diagnosed with acute leukemia. The control group consisted of 16 patients that had presented and had no malignant disease, CNS infection or chronic disease. CSF OPN levels were studied with enzyme-linked immunosorbent assay (ELISA) method. The mean CSF OPN level was 32.76±49.22 ng/ml in the patients at the time of diagnosis and 14.93±6.84 ng/ml in the control group (p>0.05). The mean CSF OPN level was 27.68±32.73 ng/ml at the time of diagnosis in the group without CNS involvement and 53.48±89.21 ng/ml in the group with CNS involvement (p>0.05). However, the CSF OPN level at the time of CNS relapse in patients who developed CNS involvement during follow-up (127.4±52 ng/ml) was significantly higher than in the group without CNS involvement at diagnosis and follow-up (mean CSF OPN level: 27.68±32.73 ng/ml) (p<0.001). The analysis of CSF OPN levels at the time of diagnosis-before relapse and at the periods of relapse and remission in patients who had CNS involvement at diagnosis and/or follow-up revealed statistically significant differences between the time points (p<0.001). High CSF OPN levels in childhood acute leukemia patients may be used as evidence for CNS involvement, and any increases found in CSF OPN levels may be a preliminary predictor for CNS involvement.

Thiol disulfide homeostasis in ionizing radiation and chemotherapeutic drug exposure.

OBJECTIVE: This study aims to reveal the oxidant and antioxidant status in nurses with chemotheropathic drug exposure and radiology unit workers exposed to ionizing radiation (IR). METHODS: Nineteen radiology unit workers, 14 nurses, and 15 controls were included the study. All of the participants using antioxidants, vitamin supplements, smokers, any therapeutic drugs, and exposed therapeutic or diagnostic X-ray or chemotherapeutic drugs in 12 months were excluded from the study. Total and native thiols, disulfide/native thiol percent ratios (SS/SH), disulfide/total thiol percent ratios, disulfide amounts, and native thiol/total thiol percent ratios, ischemia-modified albumin (IMA) were determined. RESULTS: Disulfide levels, disulfide/total thiol ratio, and disulfide/native thiol ratio of serum samples of both radiology unit workers and nurses were significantly higher and ratio of native thiol/total thiol was lower than the control group. The radiation dose in radiology unit workers was mean±SD: 0.02±0.009, median (min-max): 0.02 (0.001-0.04). Thiol-disulfide homeostasis was disturbed and the balance shifted in the direction of oxidant damage, even at low-dose IR exposure and normal range. CONCLUSION: As far as we know, the current findings first demonstrate an apparent chronic oxidative stress in the subjects who were occupationally exposed to antineoplastic drugs and radiation even if annual radiation exposure dose measurements are normal.

Evaluation of adolescents with heavy menstrual bleeding using the International Society of Thrombosis Haemostasis- Bleeding Assessment Tool and The Pediatric Bleeding Questionnaire scores.

BACKGROUND: Heavy menstrual bleeding (HMB) is a common condition in adolescents. However, bleeding disorders are known to be one of the causes of HMB in adolescent girls, so they should be considered. Simple methods that can be used in primary health care are needed to determine whether patients have bleeding disorders. The aim of this study was to evaluate the bleeding score of patients admitted with HMB and to determine the diagnostic value of patients who were symptomatic but whose initial hemostatic tests were normal. METHODS: A total of 113 adolescents with HMB and 20 healthy adolescent girls were included in the study. The Pediatric Bleeding Questionnaire (PBQ) and the International Society of Thrombosis Haemostasis-Bleeding Assessment Tool (ISTH-BAT) were used for evaluation. RESULTS: Overall, approximately 18% (n= 20) of the adolescents in the study were diagnosed with a bleeding disorder. The cut off value for the `clinically significant bleeding score` was found to be 3.5. CONCLUSIONS: The PBQ and ISTH-BAT can help distinguish a significant bleeding history from an otherwise trivial bleeding and can be included in the algorithm for the primary care of adolescents with HMB with suspected bleeding disorders.

Isocitrate Dehydrogenase 1 and 2 Mutations in Pediatric Neuroblastoma Patients.

Objective: Neuroblastoma is one of the common tumors of childhood. The demonstration of new factors such as isocitrate dehydrogenase 1 (IDH1) and isocitrate dehydrogenase 2 (IDH2) mutations will be important in the diagnosis and treatment. IDH1 and IDH2 mutations have been found in many types of cancer, such as malignant gliomas, acute myeloid leukemias, chondrosarcoma, and thyroid carcinoma. This study aimed to investigate the presence of IDH1 or IDH2 mutations in patients with neuroblastoma and to determine whether these mutations were different in terms of age, clinical findings, and response to treatment. Methods: Biopsy specimens of 25 patients with pediatric neuroblastoma patients were evaluated for IDH mutations. The clinical and laboratory features of the patients with/without mutation were retrospectively analyzed from a hospital database. Results: A total of 25 patients for whom genetic analysis could be performed were included in the study (60% male, n=15). The mean age was 32.2±25.9 months (3 days-96 months). IDH1 mutation was detected in 8 (32%) and IDH2 mutations in 5 (20%) patients. These mutations showed no statistically significant relationship with age, tumor localization, laboratory results, stage, and prognosis. However, in the case of IDH mutation, patients were diagnosed at the advanced stage. Conclusions: This study demonstrated the relationship between neuroblastoma and IDH mutation for the first time. Because to the fact that the mutation is very heterogeneous, it would be appropriate to conduct a larger series of patients in terms of the impact of the clinical significance of each mutation on the diagnosis and prognosis.

Association between polymorphisms of EPHX1 and XRCC1 genes and the risk of childhood acute lymphoblastic leukemia.

Microsomal epoxide hydrolase, EPHX1, plays a central role in the detoxification of potentially genotoxic epoxide intermediates. In this study, we firstly aimed to investigate the relationship between EPHX1 Tyr113His and His139Arg variants, and the risk of incidence of childhood acute lymphoblastic leukemia (ALL) in Turkish population, comprised of 190 healthy controls and 167 ALL patients. In exon 3 Tyr113His polymorphism, 113His/His homozygous mutant genotype with slow activity was 18.6% in ALL patients and 9% in controls, indicating 113His/His slow activity genotype was significantly associated with an increased risk of childhood ALL (OR: 2.3, 95% CI, 1.2-4.4, P = 0.01). No significant association was found between exon 4 His139Arg variant and the risk of ALL. When both exon 3 Tyr113His and exon 4 His139Arg polymorphisms were considered together, only the exon 3 113His/His, homozygous mutant, slow activity genotype with exon 4 wild-type genotype 139His/His was significantly increased the risk of ALL 2.4-fold (OR: 2.4, P = 0.02). We also evaluated whether haplotype analysis for EPHX1 Tyr113His polymorphism together with DNA protein XRCC1 Arg399Gln variant known for its deficient DNA repair capacity would represent more prominent risk factors for the development of childhood ALL. Accordingly, the co-presence of Tyr113His variant of EPHX1 and Arg399Gln variant of XRCC1 in the same individuals significantly increased the risk of childhood ALL up to 2.1-fold (OR = 2.1, P = 0.03). Moreover, homozygous mutant genotype for both genes significantly and considerably increased the risk of childhood ALL 8.5-fold (OR: 8.5, P = 0.03). In conclusion, individuals with EPHX1 113His/His slow activity genotype may not detoxify reactive carcinogenic epoxides efficiently, binding of reactive epoxides to DNA cause DNA damage. With the inadequate polymorphic DNA repair protein, XRCC1, this situation ultimately leads to significantly increased susceptibility for childhood ALL.