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Autoimmune haemolytic anaemia (AIHA) is a rare complication of allogeneic haematopoietic stem cell transplantation (HSCT), observed with an incidence of 1-5%. Paediatric age, diagnosis of non-malignant disease, lympho-depleting agents in the conditioning regimen, use of unrelated donor, graft versus host disease and infections have been associated with a higher risk of AIHA post HSCT. Post-HSCT AIHA is associated with high mortality and morbidity, and it is often very difficult to treat. Steroids and rituximab are used with a response rate around 30-50%. These and other therapeutic strategies are mainly derived from data on primary AIHA, although response rates in post-HSCT AIHA have been generally lower. Here we review the currently available data on risk factors and therapeutic options. There is a need for prospective studies in post-HSCT AIHA to guide clinicians in managing these complex patients.

BACKGROUND. Genetic defects of innate immunity impairing intestinal bacterial sensing are linked to the development of Inflammatory Bowel Disease (IBD). Although much evidence supports a role of the intestinal virome in gut homeostasis, most studies focus on intestinal viral composition rather than on host intestinal viral sensitivity. AIM. To demonstrate the association between the development of Very Early Onset IBD (VEOIBD) and variants in the IFIH1 gene which encodes MDA5, a key cytosolic sensor for viral nucleic acids. METHODS. Whole exome sequencing (WES) was performed in two independent cohorts of children with VEOIBD enrolled in Italy (n=18) and USA (n=24). Luciferase reporter assays were employed to assess MDA5 activity. An enrichment analysis was performed on IFIH1 comparing 42 VEOIBD probands with 1527 unrelated individuals without gastrointestinal or immunological issues. RESULTS. We identified rare, likely loss-of-function (LoF), IFIH1 variants in eight patients with VEOIBD from a combined cohort of 42 children. One subject, carrying a homozygous truncating variant resulting in complete LoF, experienced neonatal-onset, pan-gastrointestinal, IBD-like enteropathy plus multiple infectious episodes. The remaining seven subjects, affected by VEOIBD without immunodeficiency, were carriers of one LoF variant in IFIH1. Among these, two patients also carried a second hypomorphic variant, with partial function apparent when MDA5 was weakly stimulated. Furthermore, IFIH1 variants were significantly enriched in children with VEOIBD as compared to controls (p=0.007). CONCLUSIONS. Complete and partial MDA5 deficiency is associated with VEOIBD with variable penetrance and expressivity, suggesting a role for impaired intestinal viral sensing in IBD pathogenesis.

The first umbilical cord blood (UCB) transplantation was performed 30 years ago. UCB transplantation (UCBT) is now widely used in children with malignant and non-malignant disorders who lack a matched family donor. UCBT affords a lower incidence of graft-versus-host disease compared to alternative stem cell sources, but also presents a slower immune recovery and a high risk of infections if serotherapy is not omitted or targeted within the conditioning regimen. The selection of UCB units with high cell content and good human leucocyte antigen match is essential to improve the outcome. Techniques, such as double UCBT, ex vivo stem cell expansion and intra-bone injection of UCB, have improved cord blood engraftment, but clinical benefit remains to be demonstrated. Cell therapies derived from UCB are under evaluation as potential novel strategies to reduce relapse and viral infections following transplantation. In recent years, improvements within haploidentical transplantation have reduced the overall use of UCBT as an alternative stem cell source; however, each may have its relative merits and disadvantages and tailored use of these alternative stem cell sources may be the optimal approach.

Few studies have detected qualitative and quantitative aspects of patients who underwent HSCT during childhood. The aims of this study are to explore the most recurrent narrative themes of HSCT experience in families five years after the procedure, and to observe statistical correlations between meaning attributed to the experience and defined variables.Thirty-five families of pediatric HSCT survivors participated in the research. Both survivors and their families were asked to write a brief composition about their disease experiences. Qualitative analysis of the texts was performed using the T-LAB software. Information about medical aspects and psychological problems in HSCT survivors were collected with interviews and administering the Child Behavior Checklist 6-18.HSCT survivor families that reported the presence of externalizing and internalizing symptoms focused on thematic areas concerning broken families with separation between parents and the affected child versus healthy children.Long term psychological problems seem to be connected to the perception of family disruption. Specifically, family relationships seem to be the factor that protects from or enhances the risk of psychopathology in HSCT survivors. Moreover, the use of metaphoric terms to refer to HSCT presents higher associations with psychopathology. On the contrary, the possibility of referring directly to the transplantation is associated with psychological well-being. It is important to consider the family as a group in order to improve care.

Background: Rituximab (RTX; anti-CD20 mAb) is a treatment option in children with refractory immune thrombocytopenia, autoimmune hemolytic anemia (AHA), and Evans syndrome (ES). Prevalence and clinical course of RTX-induced hypogammaglobulinemia in these patients are poorly known. Objective: To evaluate the prevalence and risk factors for persistent hypogammaglobulinemia (PH) after RTX use. Methods: Clinical and immunologic data from children treated with RTX for immune thrombocytopenia, AHA, and ES were collected from 16 Italian centers and 1 UK center at pre-RTX time point (0), +6 months, and yearly, up to 4 years post-RTX. Patients with previously diagnosed malignancy or primary immune deficiency (PID) were excluded. Results: We analyzed 53 children treated with RTX for immune thrombocytopenia (n = 36), AHA (n = 13), and ES (n = 4). Median follow-up was 30 months (range, 12-48). Thirty-two percent of patients (17 of 53) experienced PH, defined as IgG levels less than 2 SD for age at last follow-up (>12 months after RTX). Significantly delayed B-cell recovery was observed in children experiencing PH (hazard ratio, 0.55; P

Chimeric antigen receptor (CAR) T-cell therapy is a new, effective treatment for patients with relapsed/refractory (r/r) B-cell acute lymphoblastic leukaemia (ALL). Tisagenlecleucel achieved a complete remission (CR) rate and minimal residual disease (MRD) negativity of 81% at 3 months in the pivotal study; overall survival (OS) was 76% at 12 months (Maude et al, 2018). Real world data confirmed similar outcomes, with 1-year OS of 77% and event free survival (EFS) of 52% (Pasquini et al, 2020). Relapse can occur in the form of CD19 negative or CD19 positive ALL. The latter is associated with lack of persistence of the CAR T product. B-cell aplasia (BCA) is an indirect measure of CAR T presence. Early ( In our centre, we administered maintenance therapy to a cohort of children with early loss of BCA. When compared to UK patients undergoing SCT for the same indication, we noted promising early outcomes. We report the findings here. We collected data on children with r/r ALL treated with tisagenlecleucel at Great Ormond Street Hospital (GOSH) from January 2018 to January 2021 who presented loss of BCA without evidence of disease (negative molecular or flow cytometry MRD) within 12 months from infusion. Loss of BCA was defined as peripheral B-cell count ≥0.10 x 10^9/L or bone marrow (BM) CD19+ events ≥0.1%. We compared outcomes of children who received maintenance as per UKALL 2011 protocol at GOSH to those who received SCT for the same indication from all UK paediatric centres. Fourteen patients from GOSH met the inclusion criteria. Four had loss of BCA after 6 months from CAR T infusion, none of them received additional therapy and they are all alive and in CR at a median of 535 days after CAR T infusion (Figure 1, A and B). Ten patients recovered B cells at Management of patients who experience early loss of BCA after CAR T is challenging and there are little data to support optimal treatment. In our experience, maintenance therapy compared favourably with SCT with similar rate of OS and EFS. Of note, 2/5 patients died of TRM in the SCT group highlighting the toxicity of this approach in such heavily pre-treated patients. On the other hand, maintenance is a well tolerated, low-cost treatment which can be easily delivered on an out-patient basis. Our preliminary data support investigation of this strategy in larger, prospectively-recruited cohorts of patients. Moreover, our preliminary data suggest that the time of loss of BCA is a crucial clinical parameter, as children who developed it within 2 months from infusion had the worst outcome, possibly reflecting prior therapy intensity and its impact on autologous T cells. Figure 1 Figure 1. Disclosures Amrolia: ADC Therapeutics: Other: Named inventor on a patent which is being transferred to ADCT.; Autolus: Patents & Royalties. Ghorashian: UCLB: Patents & Royalties: CARPALL; Novartis: Honoraria.

Introduction: Immunotherapies like Inotuzumab ozogamicin (InO), Blinatumomab and Chimeric antigen receptor T cell therapy (CAR-T) have revolutionized outcomes in patients with Relapse/Refractory Acute Lymphoblastic Leukaemia (R/R ALL) with event free survival (EFS) of 50% at 1 year (Maude et al. 2018). Optimal phasing of these agents has not been clearly defined and depends on antigen expression on blasts, CNS status, T cell number and prior disease response. InO, a CD22 targeting antibody-drug conjugate has proven efficacy in adults (Kantarjian et al., 2016) and children as a bridge to allogeneic stem cell transplantation (allo-SCT) with a favourable toxicity profile (Brivio et al. 2021). However, outcomes following the use of InO prior to CAR-T therapy are still not established. This study provides a retrospective analysis of children and young adults who received InO as part of pre-CAR-T management (before leucapheresis or as bridging therapy to CAR-T infusion). Methods: Patients aged 0-25years with R/R ALL were eligible for the study if they received InO pre-CAR-T therapy. Retrospective data collection was performed using a standardised form from CAR-T centres in the UK. Response to CAR-T therapy and/or relapse was evaluated at 1, 3, 6, 12 months or at last follow-up. Results were compared to a control cohort of R/R ALL patients treated with tisagenlecleucel but without preceding InO, over a contemporaneous period, at the largest paediatric CAR-T centre in the UK. Results: Fourteen patients from 5 paediatric and young adult centres in the UK received InO after screening for CAR-T therapy. InO was used pre-leucapheresis, as bridging and for both in 2, 11 and 1 respectively. Two were excluded from outcome analysis (1 adolescent with Trisomy 21 and transfusion induced hepatic siderosis died due to VOD while awaiting CAR-T production and 1 failed CAR-T manufacture despite achieving an adequate T cell harvest as per manufacturer guidance). Twelve (85%) patients were able to receive CAR-T infusion at a median of 1 month (range 0.7-5.6 months) from first InO dose. InO was well tolerated with 21% developing febrile neutropenia and grade 4 cytopenias. Use of InO pre-leucapheresis led to successful manufacture of CAR-T cells in 2/3 (66%). InO group was compared with 27 children who received CAR-T without preceding InO over the same time period. Table 1 summarises patient and CAR-T characteristics of the two groups which were comparable. Median follow-up of the InO and non-InO groups was 10 months (range 2.8- 30.1 months). In the InO group(n=12), 3 (25%) remained leukemia free at last follow up. Nine patients (75%) relapsed. All relapses occurred within 6 months from CAR-T infusion. Seven (58%) of those who relapsed died at a median of 7.8 months post CAR-T infusion and 2 (16.6%) were salvaged with further therapy. Subsequent therapy (alternate CAR-T and/or allo-SCT) was carried out in 4/12 (33%) patients in the InO group and in 5/27 (18.5%) in the non-InO group (p= 0.2). EFS was significantly higher in the non-InO group (53% vs 12%, p=0.0009), as was OS (86% vs 13%, p=0.004) (Figure 1). Conclusion: This study provides a direct comparison between two contemporaneously treated cohorts with R/R ALL receiving CAR-T therapy. InO prior to CAR T cell therapy was well tolerated despite the cohort being heavily pre-treated except for one patient who developed fatal VOD prior to CAR T cell infusion. InO was given for disease debulking, rather than to achieve MRD negativity and hence majority of the cohort (75%) received only 1 dose of InO in bridging rather than the usual schedule of three doses weekly per cycle. Outcomes for the non-InO group were comparable to those treated on the ELIANA study but the OS of the InO group was significantly lower (13% vs 86% p= 0.004). Potential reasons include an impact of InO on function of CAR-T cells in vivo or a deleterious effect of InO on the B cell compartment such that CAR-T cells prove less effective. Due to the retrospective nature of the study, it is possible there was an inherent bias to use InO in patients with more resistant disease, although the very comparable pre CAR-T bone marrow disease burden in each group suggests this was not the case. The small size of the cohorts may also have exaggerated differences in outcome. Ultimately, randomised controlled studies of InO pre-CAR-T are required before firm conclusions about its impact on outcomes post CAR-T therapy can be ascertained. Figure 1 Figure 1. Disclosures Sharplin: Kite Gilead: Honoraria; Novartis: Other: Travel Support. Nicholson: BMS/Celgene: Consultancy; Kite, a Gilead Company: Other: Conference fees, Speakers Bureau; Novartis: Consultancy, Other: Conference fees; Pfizer: Consultancy. Amrolia: ADC Therapeutics: Other: Named inventor on a patent which is being transferred to ADCT.; Autolus: Patents & Royalties. Ghorashian: Novartis: Honoraria; UCLB: Patents & Royalties.

Current treatments have reduced to less than 10% the incidence of central nervous system (CNS) relapses of pediatric acute lymphoblastic leukemia (ALL). Nevertheless, CNS relapses still account for...

Background Immune thrombocytopenia (ITP) is an acquired immune-mediated disorder characterized by isolated thrombocytopenia. Pediatric ITP patients are prone to develop autoantibodies such as antithyroglobulin (TG) and antithyroperoxidase (TPO), even in the absence of clinical signs of autoimmune disease. The aim of this multicenter retrospective study was to evaluate (1) the prevalence of positivity of antithyroid antibodies (TPO and TG) in a large cohort of pediatric patients with chronic ITP; (2) the role of autoimmune thyroiditis as a prognostic factor for chronicity of ITP. Procedure For this retrospective study, we collected data from patients diagnosed as affected by chronic ITP between 2011 and 2014 in six centers belonging to the Italian Association of Pediatric Haematology and Oncology (AIEOP). Results From the analysis of data, we found a significantly higher prevalence of antithyroid antibodies in children with chronic ITP (11.6%) than in the pediatric population (1.2%-1.3%). No correlation has been found between the platelet count and the prevalence of positive antithyroid antibodies at any detection time of the study. Conclusions The results of our study demonstrated that (1) the prevalence of positivity for antithyroid antibodies (anti-TPO and anti-TG) in pediatric patients with chronic ITP results is significantly higher than in the pediatric population; (2) autoimmune thyroiditis does not seem to play a role as a prognostic factor for chronicity of ITP in pediatric patients.

Relapse of acute lymphoblastic leukemia (ALL) may occur in extramedullary sites, mainly central nervous system (CNS) and testis. Optimal post-remissional treatment for isolated extramedullary relapse (IEMR) is still controversial. We collected data of children treated with hematopoietic stem cell transplantation (HSCT) for ALL IEMR from 1990 to 2015 in Italy. Among 281 patients, 167 had a relapse confined to CNS, 73 to testis, 14 to mediastinum, and 27 to other organs. Ninety-seven patients underwent autologous HSCT, 79 received allogeneic HSCT from a matched family donor, 75 from a matched unrelated donor, and 30 from an HLA-haploidentical donor. The 10-year overall survival was 56% and was not influenced by gender, ALL blast immune-phenotype, age, site of relapse, duration of first remission, and type of HSCT. In multivariable analysis, the only prognostic factors were disease status at HSCT and year of transplantation. Patients transplanted in third or subsequent complete remission (CR) had a risk of death 2.3 times greater than those in CR2. Children treated after 2000 had half the risk of death than those treated before that year. Our results suggest that both autologous and allogeneic HSCT may be considered for the treatment of pediatric ALL IEMR after the achievement of CR2.

Haploidentical transplantation in children can extend the opportunity for transplantation to almost every patient lacking a human leukocyte antigen (HLA)–matched donor and offer this treatment to every child with an otherwise incurable disease. Although initial attempts were associated with a high transplant-related mortality, recent insights into the biology of haploidentical transplantation, the availability of effective ex vivo large-scale graft-manipulation technology, and improved supportive care strategies have led to significantly better outcomes. Concurrently, the indication for haploidentical transplantation has been extended, including different malignant and nonmalignant conditions. Worldwide donor registries include mainly donors of Caucasian origin. Patients of non-Caucasian origin have a lower chance of finding a suitable unrelated donor. Haploidentical transplantation allows the treatment of children independently of their ethnic background in a timely fashion. One of the major advantages of using a related donor is the possibility of collecting or generating additional cellular products from the same donor to open the possibility of enhancing both the antitumor effects of the graft and the immunologic reconstitution after transplantation.

Background and objectives Lack of suitable donors and regimen related toxicity are major barriers for hematopoietic stem cell transplantation (HSCT) in patients with sickle cell disease (SCD) when employing the most frequently used Busulfan-based conditioning regimen. The aim of the study is the assessment of efficacy and toxicity of Treosulfan-based conditioning regimen for SCD also when alternative donors such as mismatched unrelated donor and haploidentical donor are employed.Methods We report our single-center experience: 11 patients with sickle cell disease received HSCT with a Treosulfan/Thiotepa/Fludarabine/Anti-thymoglobulin conditioning regimen between 2010 and 2015. The donor was a matched sibling donor (n= 7), a haploidentical parent (n= 2), a matched unrelated donor (n= 1) or a mismatched unrelated donor (n=1). The haploidentical and mismatched unrelated donor grafts were manipulated by removing TCRαβ and CD19 positive cells.Results All patients survived the procedure and achieved stable engraftment. Stable mixed chimerism but no SCD manifestation was observed in 5/11 patients. Grade III-IV regimen related toxicity was limited to mucositis and no grade III-IV graft-versus-host disease (GvHD) was observed. Organ function evaluation showed no long term pulmonary, cardiac or renal toxicity; cerebral vasculopathy improved in 3/5 evaluable patients. Gonadal failure was observed in 1/4 evaluable patients.Conclusion Our data suggest that Treosulfan retains the myeloablative potential of Busulfan while reducing the toxicity also when haploidentical or unrelated donors are employed.

Wiskott-Aldrich syndrome (WAS) is an inherited X-linked disorder characterized by microthrombocytopenia, immunodeficiency, and eczema. Hematopoietic stem cell transplantation (HSCT) is the treatment of choice. Eltrombopag, a thrombopoietin receptor agonist, may be useful to prevent bleeding while awaiting HSCT. We present a case of a male with WAS, profound thrombocytopenia, and bleeding diathesis successfully managed with eltrombopag before HSCT. Eltrombopag was given for 32 weeks obtaining a stable platelet count without any platelet transfusion. The patient did not experience any bleeding symptom. Eltrombopag may be a suitable therapeutic option for patients with WAS and severe thrombocytopenia as "bridge" to definitive cure.

Background: Immune Thrombocytopenia (ITP) is one of the most common conditions encoutered by the pediatric hematologist. Current first-line therapy includes: observation without drug therapy, corticosteroids and intravenous immune globulin. A minority of patients are refractory to first-line approaches. Second-line treatment options are: immunosuppressive agents and thrombopoietin receptor agonists (TPO-RA). Eltrombopag and Romiplostin are TPO-RA licensed for clinical use. Eltrombopag is, actually, the only TPO-RA approved in Italy (since two years ago) for children, over one year old, with a chronic and/or refractory ITP. Real life data of Eltrombopag are limited. Methods: We performed an Italian multicenter retrospective survey to study the clinical on-label use of TPO-RA, focus on Eltrombopag, in pediatric ITP. Our aims were, primarily, to bring out the prevalence of the use in clinical practice and secondarily to collect data on efficacy and toxicity. Results: We enrolled 69 pediatric ITP subjects from 15 Italian treatment centers (TC). 4 patients received Romiplostin as TPO-RA and were excluded by the analysis. 36/65 patients weer female (55%). Median age at ITP diagnosis: 6 years + 6 months (min 1 y + 2 m; max 16 y + 7 m). Median age at first Eltrombopag assumption: 11 years + 5 months (min 2 y + 0 m; max 17 y + 8 m). Accounting in 344 the total number of chronic ITP subjects treated by TC in the same observation period (July 2016-June 2018), we observed an Eltrombopag clinical use prevalence of 0.19 (95% CI 0.15 to 0.26). We underlined a "no response" to Eltrombopag (platelet count persistently less than 30000 per microliter) in 16/65 (25%); a "partial response" (platelet count between 30000 and 100000 per microliter) in 14/65 (21%) and a "complete response" (platelet count persistently up than 100000 per microliter) in 35/65 (54%). The overall response (partial or complete) was described in 49/65 (75%) children. During the follow up was seen in 16/49 (33%) subjects with initial response a platelet rise that waned to no response. There was no evidence of significant adverse events (clinicians are obliged, to monthly surveillance, by Italian drug agency for hypertransaminasemia and peripheral smear cell abnormalities). Conclusions: Our results demonstrate that Eltrombopag is a therapeutic option quite considered by Italian clinicians. Moreover, according with the percentages of clinical trials, Eltrombopag is safe and effective to rise platelet count. Further studies need to emphasize how factors favor a complete response and to know the incidence of long-term adverse effects. A prospective study designed and driven by Italian Association of Pediatric Hematology Oncology (AIEOP) Coagulation Disorders Working Group is, already, in progress. Disclosures No relevant conflicts of interest to declare.

Because survival of pediatric acute lymphoblastic leukaemia (ALL) has improved in the last years, adverse effects acquire increasing importance. Avascular osteonecrosis (ON) is a long term complication of ALL treatment affecting the patients' quality of life. Its pathogenesis recognizes multiple factors (age, race, genetics, chemotherapies and steroids). The different roles of dexamethasone (DXM) versus prednisone (PDN) is still under discussion, as dosages and rate of administration. The prevalence of ON varies in different series (0.43-17.6%). It affects mostly the weight-bearing epiphyseal bone, usually knee and hip. Multiple joint involvement is common. ON treatment is not established: efficacious drugs are not available; surgery is strongly invasive for pediatric patients (pts); among physical treatments, the use of hyperbaric oxygen therapy (HBO) is uncommon. We report our experience in children treated consecutively from 2000 to 2015 for ALL at the Pediatric Hematology Clinic of Padua, who developed ON. HBO was used in some pts with variable efficacy, suggesting its possible role in early stages. Materials and methods Prevalence ofON was assessed retrospectively in 469 pts with ALL enrolled in AIEOP 2000 Protocol (P 2000, 327 pts) and AIEOP BFM ALL 2009 Protocol (P 2009, 142 pts); median age was 5 years (yrs, range 1-17). Girls were 53% and boys 47% (Table 1). ON was defined as persistent pain in one or more major joints (hip, knee, elbow, shoulder, ankle) and peculiar radiological findings (plain XR or MRI). Severity was graded radiologically by the ARCO (Association of Research Circulation Osseous) staging system; clinically by the CTCAE v3.0. Statistical analysis was done using z- and t-tests. Results 19/469 pts (4%) developed ON of CTCAE grade 2-4. Age at leukaemia diagnosis was over 10 yrs in 17/19 pts. ON always presented during maintenance or off therapy. Median follow up after ON development in P 2000 was 54 months (range 21-170) and 28.5 months (8-48) in P 2009. The most frequent sites were knee, hip and ankle. Multiple joint involvement was frequent (11/19, 58%); 14/19 (74%) had also functional limitation at diagnosis (grade 3-4). Nine ON pts (3 in P 2000, 6 in P 2009) were at high risk, receiving higher steroid dosages than low risk (p As for ON treatment, 14/19 (74%) pts were treated conservatively; 5/19 (26%) pts underwent joint replacement; 7/19 (37%) pts received HBO (25-40 sessions, 2.5 ATA). Four children showed complete recovery or only limited disturbances; 14 pts had more severe impairment (grade 3-4, 5 joint replacements). One patient developed osteosarcoma as secondary malignancy after first line chemotherapy, TCSE and HBO. HBO results: pain improvement was not obtained in any patient. The 5 pts with ON ARCO grade II-III showed lesion stability without joint collapse at control MRI. The 2 pts with very advanced ON (grade IV) placed implants. Comparing the two consecutive Protocols (P 2000 vs P 2009), we found different prevalence of ON (0,3 % vs 8,4% respectively, p Conclusion In our experience the prevalence of symptomatic ON in pts treated with two consecutive and similar ALL protocols was 4% (19/469) as reported by literature. No asymptomatic cases were reported, probably due to lack of screening. Boys were affected similarly than girls; age was significantly higher in patients with ON (p 0.001). A marked different prevalence between the two groups (0.3% vs 8.4%) was found, without apparent role of age, gender or steroid dosages. However, a possible underdiagnosis in P 2000 can be considered, due to higher attention given recently to this problem. High risk pts developed ON more frequently (p HBO seems to stabilize the progression of early stage of ON, but it is not efficacious in advanced ON. Screening MRI could be useful for early diagnosis and to understand the utility of HBO in these cases. Disclosures No relevant conflicts of interest to declare.

Introduction We have evaluated Antithrombin (AT) values and Whole Blood Rotation Thromboelastometry (ROTEM) profiles in children affected by acute lymphoblastic leukemia (ALL), followed at the Clinic of Pediatric Hematology Oncology of Padua. L-Asparaginase, used in protocols for pediatric ALL, is an inhibitor of protein synthesis. Typical collateral effects are coagulation disturbances. Guidelines for identification of patients at risk of thrombosis and hemorrhages are not yet established. AT levels are the only reliable parameter for thrombotic risk. Very low levels of fibrinogen are not correctly detected by classical Clauss method; ROTEM test using FIBTEM is considered a valid tool to identify hypofibrinogenemia and hemorrhagic risk in surgical patients. The aim of the study was to analyze coagulation patterns during treatment with Pegilated L-Asparaginase (Peg-Asp). Methods Forty-two children (25 males, 17 females; 31 pB-ALL; 11 T-ALL; 23 at standard/medium risk; 19 at high risk) were consecutively diagnosed and treated with AIEOP BFM ALL 2009 protocol from June 2012 to March 2014. They received 3 (standard/medium risk) or 8 (high risk) doses of Peg-Asp (2500UI/mq/dose). ROTEM and AT determinations were performed at 5 fixed time-points before and after each Peg-Asp administration. Prothrombin time (PT), fibrinogen plasma levels and platelets counts were recorded. Maximum Clot Firmness (MCF; normal value 9-25 mm), measuring the maximum amplitude reached in FIBTEM thromboelastogram, assessed the specific role of fibrinogen in the whole blood clot formation following platelets inhibition by Cytocalasin D. Results: 798 AT and 706 FIBTEM tests were performed; details are reported in Table. We divided abnormal MCF in 3 grade levels. Only values of MCF >9 mm had a linear correlation with fibrinogen levels. Plasma fibrinogen values Twenty six children had a complete set of tests available during Induction phase (2 doses of Peg-Asp). They showed two different patterns of AT and MCF behavior. In 13 patients, mean AT levels decreased until 12-14 days after Peg-Asp, never being One child had a cerebral sinus thrombosis at the end of induction; one child had extensive thrombosis, strongly related to the central line used for dialysis. Thromboses were not related to fibrinogen concentrates administration or low AT levels. No bleedings were observed. Conclusions: Extensive analysis of coagulation parameters in children undergoing chemotherapy for ALL containing PEG Asp showed abnormalities of AT in 88% of patients and of MCF in 30%. These tests identified patients with significant abnormalities more closely than classical methods. Careful use of AT dosage and FIBTEM can help in managing coagulation disturbances, by identifying patients at risk and suggesting prevention measures. Table: AT and FIBTEM analysis in ALL patients Total N. pts / total N. tests AT 42/798 MCF 42/706 Pts with pathological tests AT Figure 1: Mean AT levels in ALL patients during induction (according to AT supplementation) Figure 1:. Mean AT levels in ALL patients during induction (according to AT supplementation) Figure 2: Mean MCF levels in ALL patients during induction (MCF>9 and MCF 9 and MCF Disclosures No relevant conflicts of interest to declare.

Introduction. Hypofibrinogenemia and its correlation with hemorrhagic risk is usually detected by serum fibrinogen level with Clauss test. Recently the role FIBTEM test of rotational thromboelastometry (ROTEM) has been evaluated for prevention and management of acute bleeding in intesive care and surgical settings. We applied it for monitoring fibrinogen deficiency for the first time in children affected by acute lymphoblastic leukemia (ALL) treated with Peg-asparaginase (PEG-Asp). Antithrombin levels (AT) were measured as parameter for thrombotic risk. This drug impairs protein synthesis and causes severe coagulative deficiencies, with both hemorrhagic and thrombotic complications. Guidelines for the management of coagulation abnormalities being missing, we tried to identify parameters for management and prevention. Methods. Eightytwo children (age 1-17 years, mean 6 year) affected by ALL treated with AIEOP BFM ALL 2009 protocol at our Institution were studied. Platelet count and coagulation tests (protrombin time PT/INR, activated partial tromboplastin time aPTT, AT, serum fibrinogen level (SF) at Clauss test and fibrinogen function at MCF) were performed before and after each PEG-Asp administration. We previously found linear correlation with SF levels only for MCF > 9 mm. We then tried to identify clinically significant deficiency of SF. Severe hypofibrinogenemia was considered when Clauss test showed SF levels < 1g/L. MCF limit for severe fuctional hypofibrinogenemia was considered Results. Severe hypofibrinogenemia was found in 240 Clauss test (24.3%), but only in 44 (4.5%) of MCF at FIBTEM. Only 28% of SF at Clauss test < 1 g/L had an MCF value = 2mm or at 3-4 mm in association with INR > 2.8. Fresh frozen plasma administration was avoided. No significant bleeding was observed. Severe AT deficiency was found in 287 measurements (23%) and in 57% of patients. AT deficiency was more frequent according to the number of PEG-Asp doses, in particular the percentage of affected patients increased in the different phases of chemotherapy (Table 1), being observed in all patients receiving prologed PEG-Asp therapy. AT was suggested at level of < 50%, but it was performed only in 54% of cases. Three thrombotic events were registered (3.6%) all in presence of AT levels Conclusions. The frequency of fibrinogen functional deficiency as detected by MCF level at FIBTEM was inferior than hypofibrinogenemia at Clauss test. The MCF level chosen in our study to identify a parameter for hemorrhagic risk was helpful to select patients for coagulant therapy with fibrinogen concentrates. AT deficiency was more frequent than fibrinogen deficiency and was related to the numer of PEG-Asp doses. These tests can help in the management of patients with coagulative disturbancies in order to prevent seriuos adverse events. Table 1. Frequency of MCF and AT deficiencies according to number of PEG-Asp doses N° of doses 1 2 4 10 MCF Disclosures No relevant conflicts of interest to declare.