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Standard pharmacokinetic (PK) assessments are demanding for persons with hemophilia A, requiring a 72-hour washout and 5 to 11 timed blood samples. A no-washout, single-clinic visit, sparse sampling population PK (PPK) protocol is an attractive alternative. Here, we compared PK parameters obtained with a traditional washout, 6-sampling time point PPK protocol with a no-washout, single-clinic visit, reverse 2-sampling time point PPK protocol in persons with severe hemophilia A (SHA) receiving ADVATE. A total of 39 inhibitor-negative males with SHA (factor VIII activity [FVIII:C]

Preventing factor VIII (FVIII) inhibitors following replacement therapies with FVIII products in patients with hemophilia A remains an unmet medical need. Better understanding of the early events of evolving FVIII inhibitors is essential for risk identification and the design of novel strategies to prevent inhibitor development. The Hemophilia Inhibitor Previously Untreated Patients (PUPs) Study (HIPS; www.clinicaltrials.gov #NCT01652027) is the first prospective cohort study to evaluate comprehensive changes in the immune system during the first 50 exposure days (EDs) to FVIII in patients with severe hemophilia A. HIPS participants were enrolled prior to their first exposure to FVIII or blood products (“true PUPs”) and were evaluated for different immunological and clinical parameters at specified time points during their first 50 EDs to a single source of recombinant FVIII. Longitudinal antibody data resulting from this study indicate that there are 4 subgroups of patients expressing distinct signatures of FVIII-binding antibodies. Subgroup 1 did not develop any detectable FVIII-binding immunoglobulin G (IgG) antibodies. Subgroup 2 developed nonneutralizing, FVIII-binding IgG1 antibodies, but other FVIII-binding IgG subclasses were not observed. Subgroup 3 developed transient FVIII inhibitors associated with FVIII-binding IgG1 antibodies, similar to subgroup 2. Subgroup 4 developed persistent FVIII inhibitors associated with an initial development of high-affinity, FVIII-binding IgG1 antibodies, followed by IgG3 and IgG4 antibodies. Appearance of FVIII-binding IgG3 was always associated with persistent FVIII inhibitors and the subsequent development of FVIII-binding IgG4. Some of the antibody signatures identified in HIPS could serve as candidates for early biomarkers of FVIII inhibitor development.

International audience; Introduction - Antihaemophilic factor (recombinant) (rAHF; ADVATE ) is approved for prophylaxis and treatment of bleeding in children and adults with haemophilia A. Reconstitution in 2 mL sterile water for injection instead of 5 mL allows for a 60% reduction in infusion volume and administration time, but could increase the likelihood of hypersensitivity and infusion-related reactions, especially in children. Aim - To assess local tolerability, safety and effectiveness of rAHF 2 mL during routine clinical practice factor VIII (FVIII) replacement (on-demand and prophylaxis) in children with severe (FVIII

The objective of this scoping review is to summarize the current use of pharmacokinetics for tailoring prophylaxis in hemophilia patients switching between clotting factor products. Patients with hemophilia may require switching of clotting factor concentrates due to a variety of factors, but there have been perceived risks associated with switching, such as inhibitor development or suboptimal protection due to inadequate dosing while titrating treatment. Studies that look at patients switching from one clotting factor concentrate to another are categorized in terms of their primary and/or secondary objectives, notably biosimilarity and comparative pharmacokinetic studies and inhibitor development studies. Research on how best to switch concentrates with respect to dosing regimen are lacking, and currently a trial-and-error approach is used for dosing the new factor concentrate. In the future, studies looking at the predictability of pharmacokinetics (PK) of a new factor concentrate based on individual PK knowledge of the original factor concentrate may offer clinical benefit by providing a safer switching approach and protocol.

Diamond-Blackfan anemia (DBA) is a rare congenital erythroid aplasia, underlied by haploinsufficient mutations in genes coding for ribosomal proteins (RP) in approximately 70% of cases. DBA is frequently associated with somatic malformations, endocrine dysfunction and with an increased predisposition to cancer. Here we present clinical and genetic characteristics of 62 patients from 52 families enrolled in the Czech and Slovak DBA Registry. Whole exome sequencing (WES) and array comparative genomic hybridization (aCGH) were employed to identify causative mutations in newly diagnosed patients and in cases with previously unrecognized molecular pathology. RP mutation detection rate was 81% (50/62 patients). This included 8 novel point mutations and 4 large deletions encompassing some of the RP genes. Malignant or predisposing condition developed in 8/62 patients (13%): myelodysplastic syndrome in 3 patients; breast cancer in 2 patients; colorectal cancer plus ocular tumor, diffuse large B-cell lymphoma and multiple myeloma each in one case. These patients exclusively harbored RPL5, RPL11 or RPS19 mutations. Array CGH is beneficial for detection of novel mutations in DBA due to its capacity to detect larger chromosomal aberrations. Despite the importance of genotype-phenotype correlation in DBA, phenotypic differences among family members harboring an identical mutation were observed.

Objectives\ud \ud In a separate document, we have provided specific guidance on performing individual pharmacokinetic (PK) studies using limited samples in persons with hemophilia with the goal to optimize prophylaxis with clotting factor concentrates. This paper, intended for clinicians, aims to describe how to interpret and apply PK properties obtained in persons with hemophilia. \ud \ud \ud Methods\ud \ud The members of the Working Party on population PK (PopPK) of the ISTH SSC Subcommittee on Factor VIII and IX and rare bleeding disorders, together with additional hemophilia and PK experts, completed a survey and ranking exercise whereby key areas of interest in the field were identified. The group had regular web conferences to refine the manuscript’s scope and structure, taking into account comments from the external feedback to the earlier document. \ud \ud \ud Results\ud \ud Many clinical decisions in hemophilia are based on some form of explicit or implicit PK assessment. Individual patient PK profiles can be analyzed through traditional or PopPK methods, with the latter providing the advantage of fewer samples needing to be collected on any prophylaxis regimen, and without the need the for a washout period. The most useful presentation of PK results for clinical decision making are a curve of the factor activity level over time, the time to achieve a certain activity level, or related parameters like half‐life or exposure (AUC). Software platforms have been developed to deliver this information to clinicians at the point of care. Key characteristics of studies measuring average PK parameters were reviewed, outlining what makes a credible head‐to‐head comparison among different concentrates. Large data collections of PK and treatment outcomes currently ongoing will advance care in the future. \ud \ud \ud Conclusions\ud \ud Traditionally used to compare different concentrates, PK can support tailoring of hemophilia treatment by individual profiling, which is greatly simplified by adopting a PopPK/Bayesian method and limited sampling protocol.

Recently, analyses on inhibitor development according to concentrate in previously untreated patients (PUPs) from two national cohort studies have been published. A similar analysis has been performed on the first 4 years of data collection of the European Haemophilia Safety Surveillance System (EUHASS) project. Together with the initial report from the RODIN study published in 2013 [4], these publications provide data on a very considerable number of patients, almost exclusively originating from Europe. Reporting to multiple registries is common, and a rare disease such as haemophilia is no exception. Although the FranceCoag study, the UKHCDO study and the EUHASS study excluded patients overlapping with the RODIN study from their analyses, the additional overlap between the EUHASS, the FranceCoag and UKHCDO studies has not been previously reported. The analysis of non-overlapping data from the EUHASS study has the potential to contribute to the ongoing discussion about the perceived increased inhibitor risk associated with the use of specific recombinant Factor VIII concentrates. Thus, we hereby provide additional analyses of the data from the EUHASS study., peer-reviewed

Thirty-two consecutive children aged 0–18 years with VTE treated with LMWH administered as a continuous infusion (CI) were identified at the Children's University Hospital Brno. The treatment led to at least partial resolution of the thrombus within two weeks in 85% of patients. There were no adverse events or increased bleeding reported in any patients. No recurrences were observed during a followup period of 6 months. Although continuous infusion should not replace subcutaneous (SC) administration of LMWH, CI appeared to be safe and efficient and may provide an alternate method of administering LMWH in a subset of the paediatric population where SC administration may not be feasible. Further prospective studies are needed to support the promising findings of our pilot clinical observation.

Introduction Clearance of infused factor VIII (FVIII) varies approximately 2-fold between persons with severe hemophilia A. This results in significant interpatient differences in factor levels following an infusion of FVIII and contributes to potentially significant differences in protection against spontaneous musculoskeletal bleeding in patients on fixed dose prophylaxis regimens. Aim The aim of this study is to compare two PK protocols: 1) a 6-point PK protocol with a 72 hour washout; and 2) a 2-point, one clinic visit PK protocol with no washout using the following pharmacokinetic (PK) parameters: clearance (Cl) and time to FVIII:C of 1% above baseline (tt1%) in persons with severe hemophilia A. Methods Inhibitor negative males with severe hemophilia A (FVIII Results 28 males (median age: 12 years, range: 2-69 years) participated. The frequency distribution of clearance and the median half-life (t1/2) generated using myPKFiT is presented in Figure 1. There was a substantial to almost perfect agreement observed when comparing the PK parameters derived from the 6-point PK protocol with washout using the two PK programs (Table 1). There was a moderate to almost perfect agreement observed when comparing the PK parameters derived from the 6-point PK protocol with washout to the 2-point PK protocol with no washout using the myPKFiT program (Table 2). Conclusion The 2-point, one clinic visit, PK protocol (24 and 3 hrs) with no washout offers a convenient and practical approach to generating clinically relevant PK parameters in persons with severe hemophilia A. It can provide information relevant to selection of personalized prophylaxis regimens that aim to reduce to a minimum/eliminate spontaneous joint bleeding. Disclosures Blanchette: Shire: Other: Investigator-initiated research funding; Novo Nordisk: Other: Speaker's fees; Shire: Other: Speaker's fees; Bayer: Other: speaker's fees; Bioverativ: Other: Investigator-initiated research funding; Pfizer: Other: Speaker's fees. Jackson:Pfizer: Honoraria; Roche: Honoraria; Bayer: Honoraria; Novo Nordisk: Honoraria; Shire: Honoraria; Bioverativ: Other: Investigator initiated grant funding. Carcao:Octapharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; LFB: Honoraria, Membership on an entity's Board of Directors or advisory committees; CSL-Behring: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novo Nordisk: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Biotest: Honoraria, Membership on an entity's Board of Directors or advisory committees; Grifols: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bioverativ/Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Khoo:Shire: Research Funding; Biogen Idec: Research Funding. Blatny:Shire, Pfizer, Roche: Consultancy, Speakers Bureau.

Background and objectives FVIII inhibitors remain the major complication of replacement therapy in hemophilia A. Why some patients develop inhibitors whereas others do not is poorly understood. The Hemophilia Inhibitor PUP Study (HIPS, clinicaltrials.gov NCT01652027), a prospective multicenter observational study, aim to identify early immune biomarkers which predict inhibitor development in previously untreated patients (PUPs) with severe hemophilia A. Such biomarkers would facilitate early risk identification and the initiation of potential immune intervention strategies. Previously we reported time-resolved antibody data for the first 15 patients who completed antibody analysis (Gangadharan 2017). Here we present data from all 25 patients enrolled in HIPS, identifying four distinct patient subgroups based on their unique antibody signatures. We also summarize data for F8 mutations and longitudinal data of circulating immune cells such as FoxP3+ T cells (Tregs), Th17 cells, and granulysin+ cells. Methods FVIII inhibitor testing (Nijmegen method, performed in the central laboratory Medical University of Vienna) and antibody analytics were assessed prior to first exposure, 7-9 days after exposure day (ED) 1 and 5-7 days after EDs 5, 10, 20, 30, 40, and 50. FVIII-specific advanced antibody analytics were performed using methodology described by Whelan 2013 and Hofbauer 2015. FVIII mutational analysis was performed at Bloodworks Northwest, Seattle. Longitudinal epigenetic cell counting in whole blood using quantitative PCR-based methylation assays (www.epiontis.com) was done to monitor changes in peripheral FoxP3+ T cells (Tregs), pro-inflammatory Th17 cells, and granulysin+ cells. Results Our data reveal 4 different subgroups of patients associated with distinct signatures of FVIII-specific antibodies. The first subgroup includes 7 subjects who developed FVIII inhibitors by study criteria (B.U. > 0.6 B.U. x 2 measurements from consecutive study days in central laboratory). All 7 subjects had high-risk F8 gene mutations including large deletions (2), intron 22 inversions (4) and duplications (1). Inhibitors in these patients were associated with the development of high-affinity class-switched FVIII-specific antibodies which were detected prior to the first detection of inhibitors. High-affinity IgG1 was generally observed first, followed by high affinity IgG3 and subsequently high-affinity IgG4. Other isotypes and IgG subclasses of anti-FVIII antibodies were only seen occasionally. The second subgroup includes 2 subjects with low titer inhibitors. One subject, who expressed an intron 22 inversion, had a transient low titer FVIII inhibitor (1.4 BU/ml) which was associated with a high-affinity IgG1 antibody only. The other subject, who expressed a frame shift mutation, developed high affinity IgG1 by ED1. This patient had a low titer inhibitor detected (0.8 BU/ml) at ED20 which remained low (0.5 BU/ml) at study end, ED50. No other IgG subclasses were observed in either patient. The third subgroup includes 7 subjects with non-neutralizing antibodies. These subjects expressed intron 22 inversions (3), missense mutations (3) or an intron 1 inversion (1). Six of these patients developed low-affinity IgG1 antibodies which were observed until study end without the appearance of high-affinity antibodies or any other IgG-subclass. No FVIII inhibitors were detected at any time. The remaining subject initially developed low-affinity IgG1 antibodies and subsequently high-affinity IgG1 which remained until study end. No other IgG subclasses and no FVIII inhibitor were detected. The fourth subgroup includes 7 subject who never developed any FVIII-specific antibodies or FVIII inhibitors. These patients expressed missense mutations (3), an intron 22 inversion (1), a duplication (1), a frameshift mutation (1) or a nonsense mutation (1). Relative proportions of circulating FoxP3+ T cells (Tregs), Th17 cells or granulysin+ cells did not correlate with the development of FVIII inhibitors or FVIII-specific antibodies in individual PUPs. Conclusions Data obtained from the HIPS study identify four distinct patient subgroups based on their specific antibody signatures. Most importantly, high affinity class-switched antibodies preceded clinical inhibitor detection, substantiating their potential role as suitable predictive biomarkers for inhibitor development. Disclosures Gangadharan: Shire: Employment. Reipert:Shire: Employment, Equity Ownership. Berg:Research Institute for Applied Bioanalytics and Drug Development, IMC Fachhochschule Krems /: Research Funding. Scheiflinger:Shire: Employment, Equity Ownership. Blatny:Shire, Pfizer, Roche: Consultancy, Speakers Bureau. Fijnvandraat:CSL Behring, Bayer, Shire: Membership on an entity's Board of Directors or advisory committees, Research Funding. Gruppo:Shire: Honoraria, Membership on an entity's Board of Directors or advisory committees. Male:CSL Behring: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bayer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Biotest: Speakers Bureau; Novo Nordisk: Speakers Bureau; Octapharma: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shire: Speakers Bureau; SOBI: Speakers Bureau. McGuinn:Shire: Research Funding; BioMarin: Consultancy; CSL Behring: Consultancy; Pfizer: Research Funding; Spark: Consultancy, Research Funding; Bioverativ: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Consultancy. Meeks:HEMA Biologics: Other: Advisory Board; Genentech: Other: Advisory Board; Catalyst Biosciences: Other: Advisory Board; CSL Behring: Other: Advisory Board; Bayer: Other: Advisory Board; Bioverativ: Other: Advisory Board; Shire: Other: Advisory Board; Pfizer: Research Funding. Ragni:MOGAM: Membership on an entity's Board of Directors or advisory committees; Shire: Research Funding; Sangamo: Research Funding; SPARK: Consultancy, Research Funding; Novo Nordisk: Research Funding; Biomarin: Membership on an entity's Board of Directors or advisory committees, Research Funding; CSL Behring: Research Funding; Alnylam: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bioverativ: Consultancy, Research Funding. Recht:Shire: Research Funding; Biogen: Research Funding; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kedrion: Membership on an entity's Board of Directors or advisory committees. Santagostino:Bayer, Shire, CSL Behring, Pfizer, Novo Nordisk, Grifols, Kedrion, Sobi, Bioverativ, Octapharma, Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Shapiro:Bayer Healthcare: Other: International Network of Pediatric Hemophilia; Octapharma: Research Funding; Prometic Life Sciences: Consultancy, Research Funding; Daiichi Sankyo: Research Funding; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genetech: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bio Products Laboratory: Consultancy; Shire: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sangamo Biosciences: Consultancy; Kedrion Biopharma: Consultancy, Research Funding; Bioverativ, a Sanofi Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; OPKO: Research Funding; BioMarin: Research Funding. Staber:NovoNordisk: Consultancy; Bayer: Honoraria; uniQure: Honoraria. Brown:Shire: Research Funding.

Numerous recent reports have described the use of recombinant factor VIIa (rFVIIa) in non-hemophilia bleeding Situations for achievement of hemostasis. However, its use in clinical situations other than hemophilia patients with inhibitors has been complicated by some reports of thrombotic events. rFVIIa has been used successfully to treat coagulopathic and/or bleeding neonates. The prevalence of thrombotic events in these neonates is completely unknown. This study was initiated to determine the risk of thrombotic events associated with rFVIIa use in neonates. Procedure. All published literature in non-hemophilic, non-congenital factor VII deficient neonates receiving rFVIIa was reviewed. In addition, all data submitted to the SeveN Bleep Registry, a web-based registry of rFVIIa uses in non-hemophilic children was analyzed.

X-linked neutropenia (XLN, OMIM #300299) is a rare form of severe congenital neutropenia. It was originally described in a three-generation family with five affected members that had an L270P mutation in the GTP-ase binding domain (GBD) of the Wiskott-Aldrich syndrome protein (WASP) [Devriendt et al (2001) Nature Genetics, Vol. 27, 313-317]. Here, we report and describe a large three-generation family with XLN, with 10 affected males and eight female carriers. A c.882T>C mutation was identified in the WAS gene, resulting in an I294T mutation. The infectious course is variable and mild in view of the profound neutropenia. In addition to the original description, low-normal IgA levels, low to low-normal platelet counts and reduced natural killer (NK)-cell counts also appear as consistent XLN features. However, inverted CD4/CD8 ratios were not found in this family, nor were cases identified with myelodysplastic syndrome or acute myeloid leukaemia. Female carriers exhibited a variable attenuated phenotype. Like L270P WASP, I294T WASP is constitutively active towards actin polymerization. In conclusion, this largest XLN kindred identified to date provides new independent genetic evidence that mutations disrupting the auto-inhibitory GBD of WASP are the cause of XLN. Reduced NK cells, low to low normal platelet counts and low to low-normal IgA levels are also features of XLN.

Our objective was to assess the incidence of inhibitors development in Czech Republic since the introduction of recombinant factor VIII (rFVIII) and to look for the factors potentially influencing this parameter. It is to be expected that inhibitors risk may be increased after the introduction of recombinant products. Data of Czech National Haemophilia Programme registry entered from 2003 till 2013 were analysed. Both annual and absolute incidences of newly developed inhibitors in previously untreated patients (PUPs) were calculated. Bleeding and treatment data were also extracted, and association to the treatment regimen and development of inhibitors were analysed. Within the given period, we commenced 45 PUPs with haemophilia A on rFVIII and treated them for 137 treatment-years. Twenty-two of the PUPs had severe haemophilia A, being treated for 88 treatment-years. Treatment strategy for them was prophylaxis. Other PUPs were treated on demand. Median annual bleeding rate was 5 for boys with severe haemophilia, 3 for moderate haemophilia and 1 for mild form of the disease. No inhibitors developed in PUPs with moderate/mild haemophilia A. Annual inhibitor incidence rate in PUPs with severe haemophilia A treated with rFVIII was 56.8 per 1000 treatment-years. Absolute incidence was 22.7% (5/22). All inhibitors appeared within the first 50 exposure days. Comparing rFVIII-treated group with the control group treated under same/similar conditions with plasma-derived FVIII during the same follow-up period, we were not able to find significant difference in inhibitor development between these two groups. Our results support the finding that use of rFVIII is not a proven risk factor for inhibitor development in patients with haemophilia A.

Background: Evidence about inhibitor formation in non-severe haemophilia and the potential role for clotting factor concentrate type is scant., Aim: To report inhibitor development in non-severe haemophilia patients enrolled in the European Haemophilia Safety Surveillance (EUHASS) study., Methods: Inhibitors are reported quarterly and total treated patients annually. Incidence rates and 95% Confidence Intervals (95% CI) were calculated according to diagnosis and concentrate used., Results: Between 1-10-2008 and 31-12-2012, 68 centres reported on 7969 patients with non-severe haemophilia A and 1863 patients with non-severe haemophilia B. For haemophilia A, 37 inhibitors occurred in 8622 treatment years, resulting in an inhibitor rate of 0.43/100 treatment years (95% CI 0.30-0.59). Inhibitors occurred at a median age of 35 years, after a median of 38 exposure days (EDs; P25-P75: 20-80); with 72% occurring within the first 50 EDs. In haemophilia B, one inhibitor was detected in 2149 treatment years, resulting in an inhibitor rate of 0.05/100 years (CI 0.001-0.26). This inhibitor developed at age 6 years, after 6 EDs. The rate of inhibitors appeared similar across recombinant and plasma derived FVIII concentrates. Rates for individual concentrates could not be calculated at this stage due to low number of events., Conclusion: Inhibitors in non-severe haemophilia occur three times more frequently than in previously treated patients with severe haemophilia at a rate of 0.43/100 patient years (haemophilia A) and 0.05/100 years (haemophilia B). Although the majority of Inhibitors developed in the first 50 EDs, inhibitor development continued with increasing exposure to FVIII., peer-reviewed

The ISTH SSC on Factor VIII/IX has previously issued guidelines for studies assessing the pharmacokinetics (PK) of factor concentrates [1,2]. They suggested drawing 10 or 11 blood samples over a period of 32-48h or 50-72h, after infusing 25-50 or 50-75 IU/kg, respectively for factor VIII (FVIII) or factor IX (FIX), in cohorts of 12-15 patients with a crossover design. Such PK studies are not ideal for tailoring the treatment of individual patients, mostly for the requirement of several blood samples. Due to broad inter-individual variation, the individual disposition of FVIII and FIX cannot be predicted from morphometric characteristics and average PK parameters, but requires empirical assessment in each individual [3–6]. Previous guidance of this ISTH SSC described the PK methodology for the prediction of individual trough levels of FVIII [7]. The present communication, building on recent advancements in the population PK (PopPK) of FVIII and FIX [8], adds to the former documents.

Diamond-Blackfan anemia is a rare inherited bone marrow failure syndrome diagnosed in early infancy that is characterized by a (a) macrocytic anemia with no other significant cytopenia, (b) reticulocytopenia, and (c) normal bone marrow cellularity with a paucity of erythroid precursors. Physical anomalies are often present. Mutations in several ribosomal proteins have been associated with the disease. Here we present a detailed description of 39 patients from 34 families enrolled in the Czech National Diamond-Blackfan Anemia Registry. Erythrocyte adenosine deaminase activity and serum erythropoietin levels were measured and bone marrow analysis and clonogenic assays were carried out. Twenty-two different ribosomal proteins were sequenced. We identified mutations in five different ribosomal proteins in 28/39 patients (71.8%) from 23/34 families (67.6%). Several new mutations are described. The most interesting data relate to genotype–phenotype correlations. All patients with ribosomal protein L5 or ribosomal protein L11 mutations have a thumb defect usually with one or more other anomalies. Most of these patients were born small for gestational age and currently have short stature. We also described five patients with a ribosomal protein S26 mutation. All of the latter are transfusion-dependent and they exhibit skeletal abnormalities rather than thumb or craniofacial deformities. Patients with ribosomal protein S19 seem to bear mildest associated anomalies, usually in a craniofacial region.

Many patients with haemophilia develop inhibitors to factor VIII and require bypassing agents to provide haemostatic cover for limb- or life-threatening bleeding episodes. Due to the reduced risk of blood-borne pathogen transmission with recombinant products, on-demand recombinant factor VIIa (rFVIIa; NovoSeven is the treatment of choice for children with inhibitors. In haemophiliac patients without inhibitors, primary prophylaxis has been clinical practice for several years. This paper summarises 13 case histories of rFVIIa secondary prophylaxis for haemophilia patients with inhibitors. This was a retrospective survey of adult and paediatric severe haemophilia patients with inhibitors treated with rFVIIa from ten European Haemophilia Centres. There was a wide variation in administered rFVIIa dose, from 200-250 microg kg(-1) per week to 220 microg kg(-1) daily. In many cases, this was lower than the recommended on-demand dose of rFVIIa. In 12/13 cases, prophylaxis with rFVIIa considerably reduced the number of bleeding episodes compared with previous treatment. Eight/nine patients were satisfied or very satisfied with rFVIIa treatment, and in cases reporting subjective quality of life (QoL), all were improved, much improved, or significantly improved. In haemophilia patients with inhibitors, prophylaxis with rFVIIa is highly effective in reducing the number of bleeding episodes and results in good patient compliance and improved QoL. Randomised controlled trials are needed to confirm these findings. Results of a recently completed clinical trial on secondary prophylaxis with rFVIIa in frequently bleeding haemophilia patients with inhibitors are expected in late 2006.

Invasive fungal infection continues to pose a significant threat to immunocompromised patients, with cerebral aspergillosis being among the most feared ones. The authors describe an adolescent girl with acute lymphoblastic leukemia (ALL) with subsequent acute liver failure, who developed an aspergillus brain abscess. The patient was treated with combined antifungal therapy using amphotericin B local instillation, prolonged systemic amphotericin B colloidal dispersion along with vinca alkaloids-containing chemotherapy, followed by neurosurgical debridement and oral voriconazole in the setting of ongoing antileukemic maintenance chemotherapy. Her ALL remains now in complete remission 30 months from diagnosis, with no evidence of fungal infection.

Congenital afibrinogenemia is very rare inherited bleeding disorder, caused by absence of fibrinogen in plasma. Serious spontaneous bleeding including intracranial haemorrhage may occur at any age. We present a case report of a boy with afibrinogenemia caused by novel mutation – homozygous deletion Aα 6477A. Diagnosis was set after bleeding post cleft lip and palate plastic surgery. Spontaneous intracranial haematoma in occipital region occurred when the boy was 11 month old. Replacement therapy with plasma derived fibrinogen concentrate successfully covered neurosurgical evacuation of hematoma. The patient was then commenced on regular prophylaxis with fibrinogen concentrate two times a week. No further bleeding episodes occurred until present time. Spontaneous intracranial bleeding in patients with inherited bleeding disorders is often life threatening. Immediate replacement therapy is crucial, together with diagnostics and surgery, when necessary. Prophylactic substitution therapy after a severe bleeding episode is recommended. Disclosures No relevant conflicts of interest to declare.

Background Inhibitor development is a complex, multifactorial immune response involving both patient-specific and treatment-related factors. Of the known risk factors, intensive treatment at an early age has been shown to be significant, and clinical observations have suggested that early prophylaxis (i.e. first exposure to FVIII in the absence of a bleed in the first year of age) may protect patients from inhibitor development by inducing FVIII tolerance. Aim This study aimed to assess prospectively if a once-weekly, low-dose prophylactic regimen started before 1 year of age and before the onset of a severe bleeding phenotype (i.e. joint bleed), together with the minimization of immunological danger signals, could reduce the incidence of inhibitor formation in PUPs with severe and moderately severe hemophilia A to 15% or less. Methods The EPIC study was a Phase 3b, prospective, single arm, historically-controlled, international multicenter study to assess the incidence rate of inhibitor formation in PUPs with severe and moderately severe hemophilia A during the first 50 exposure days (EDs) of treatment with ADVATE starting with a once-weekly, low-dose (ADVATE 25 IU/kg once weekly), prophylactic regimen. If clinically indicated, it was permissible to increase the frequency of dosing to 2 or 3 times per week. In addition, infusions during the first 20 EDs had to be given 3 to 4 days before or after any vaccinations, which had to be given subcutaneously, not intramuscularly; infusions had to be avoided if the subject had high fever (above 38°C [100°F]). Main enrolment criteria were: severe and moderately severe hemophilia A (FVIII ≤2%), age Results A total of 22 subjects were enrolled in the study. Of 20 subjects who met all entry criteria, 19 received treatment; of these, all had severe hemophilia A (FVIII0.6 BU in PUPs were 27%. A total of 67 major protocol deviations (PD) were reported in 15 patients: 44 PDs of these were reported in 10 subjects and were related to the treatment regimen and therefore have contrasted with the protocol intention, which was to minimize immunological danger signals and low dose prophylactic regimen. As a result of the observed inhibitor incidence the study was terminated based on futility analysis, i.e. the probability to achieve the primary end-point of inhibitor rate reduction to ≤15%. Details on inhibitor patients will be presented. Discussion The EPIC study showed no safety issue as confirmed by the Data Safety Monitoring Board. To align treatment decisions in the presence of danger signals (which are not completely avoidable in children around 1 year of age) with a demanding study protocol was found to be challenging. Thus the hypothesis that an early low dose prophylaxis in the absence of immunological danger signals might reduce inhibitor incidence in PUPs with hemophilia A could neither be verified nor disproved within this study. Disclosures: Auerswald: Novo Nordisk: Consultancy, Research Funding; Biotest: Consultancy, Research Funding; CSL-Behring: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; Baxter: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. Kurnik:Baxter: Consultancy, Research Funding; Bayer: Consultancy, Research Funding; Biotest: Consultancy, Research Funding; CSL-Behring: Consultancy, Research Funding; Novo Nordisk: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. Blatny:Baxter: speaker fee Other. Reininger:Baxter Innovations GmbH: Employment.

Abstract 1342 Introduction. Aplastic anemia (AA) and myelodysplastic syndrome (MDS) are rare diseases in childhood. The most common subtype of MDS is refractory cytopenia (RC). Both diseases typically exhibit with overlapping features and in both disorders dysregulation of immune system variably contributes to the degree of bone marrow (BM) failure. In the diagnostic algorithm plays role also analysis of consecutive BM samples by morphology. Patients and methods. Patients diagnosed between 2005 – 2011 with at least two BM samples analyzed by flow cytometry (FC) before treatment has started and with centrally evaluated BM biopsy according to EWOG MDS criteria were included into the study. We compared first and the last available sample before treatment (immunosupression or stem cell transplantation). By FC we analyzed following parameters: cell subsets (granulocytes, monocytes, lymphoid cells, erythroid precursors), BM precursors (CD34pos, CD117pos), T cells (CD3pos, CD3pos4pos, CD3pos8pos, CD3posHLA DRpos out of all cells, HLA DRpos out of CD3pos/CD3pos4pos/CD3pos8pos cells); B cells (CD19pos, CD19pos10pos, CD19pos45dim to neg, CD19pos34posout of all cells, CD10pos and CD20pos10neg out of CD19pos). In total 22 patients with AA (12 girls, 10 boys, mean age 11 years; 1.1–18 years) and 20 patients with RC (11 girls, 9 boys, mean age 11 years; 3.7–18) were included into the study. Median of time interval between both samples was 139 (1–1343) days in RC and 15 (1–56) days in AA. WT1 expression on mRNA level was analyzed in the sample before treatment with the highest number of CD34pos precursors to avoid blood contamination. All patients were screened by FISH for changes on chromosome 7 and 8. We asked following questions: Are there differences in the parameters in both bone marrow samples between SAA and RC? Is there any different pattern between d0 and before therapy sample between AA and RC? Are there any differences in WT1 expression between AA and RC group? Results. RC and AA significantly differ in both time points. AA patients have significantly decreased precursors (CD34, CD117); the difference is more pronounced at the later time point. More lymphocytes (both B and T) and less granulocytes are present at later time point in AA patients (p Conclusion. By FC statistical differences can be identified in both samples (d0 and before treatment) between RC and AA. More pronounced differences are at later time point, which can be explained by further destruction of precursor and myeloid compartment more pronounced in AA patients compared to RC. WT1 expression is typically high in patients with RC and monosomy 7. Disclosures: No relevant conflicts of interest to declare.

Abstract 3651 Introduction: SeveN Bleep (Seven A in Nonhemophilia Bleeding in Pediatrics) is a web-based registry for collecting data on the use of rFVIIa in the treatment of severe and/or life threatening bleeding in children without hemophilia. The registry was endorsed by the Paediatric/Perinatal SSC subcommittee of ISTH. Methods: The registry was established in 2005. During the five years of its existence, 191 cases were recorded, of which 164 (86%) records fulfilled the validation criteria and were eligible for further analyses. For the purpose of analysis, the patients were stratified into two groups: neonates and infants 1 yr old. Statistical methods were used as appropriate. Results: Fifty nine (36%) valid records described the treatment with rFVIIa in neonates and infants, and 105 (64%) in older children. Of these, 27(16%) were for the prevention of severe bleeding. In the rest (84%) of cases, rFVIIa was used to treat severe bleeding. Those 137 cases (42 neonates+infants and 95 older children) were further analysed for the purpose of this report. The median weight in the In those older than 1 year, the median age was 10 years and median weight 30 kg. The reasons for administration of rFVIIa included trauma (45%), “non-trauma” surgery (14%) and bleeding related to malignancy and/or its treatment (11%). Survival rate in this group was 72%. 17% of deaths were related to the underlying hemorrhage treated. There were no thrombotic event or death related to rFVIIa treatment recorded in this group. There was a trend towards using a higher total dose (median 160ug/kg) in patients that died compared to a lower dose (median 120 ug/kg) in those who survived (p=0.078). In addition, those who survived needed lesser number of doses as compared to the deceased patients (median number of doses 1 and 2, respectively; p=0.052). Use of rFVIIa led to a significant decrease in the consumption of blood products in the 24 hour period after rFVIIa administration compared to the 24 hours prior to the use of rFVIIa - packed red cells (280 ml vs. 560 ml; p=0.001), FFP (250 ml vs. 500 ml; p=0.003). There were also significant changes in certain laboratory parameters related to rFVIIa administration also. Estimated blood loss decreased from 30 ml/kg prior to rFVIIa administration to 3 ml/kg after the use of rFVIIa (p=0.002). Conclusion: SevNBleep registry has proven to be a useful international tool for collection of relevant clinical data on the use of rFVIIa. rFVIIa appears to be beneficial in the management of bleeding in the pediatric population. The prevalence of adverse events related to use of rFVIIa was very low, though not absent. To minimize the potential bias related to reporting of SAEs, all major contributing centers has been contacted for further information with regards to consecutive reporting of patients treated with rFVIIa. Disclosures: Off Label Use: rFVIIa use in life threatening bleeding in children.

Abstract 3802 Poster Board III-738 Introduction Monosomy 7 or del(7q) are frequent cytogenetic abnormalities in children with myelodysplastic syndrome (MDS) and associates with poor prognosis. MDS globally affects all cellular subsets in bone marrow and in peripheral blood. We asked whether flow cytometry (FC) can separate individual subtypes of MDS from each other and from aplastic anemia (SAA) and whether in individual subtypes of childhood MDS can separate patients with and without monosomy 7. Patients/analyzed parameters In total we analyzed 94 children with centrally analyzed immunophenotype in the reference lab who were diagnosed and treated for MDS or SAA between 1998 and 2009. In total we analyzed 14 patients with refractory cytopenia, 37 patients with advanced forms of MDS (JMML 10, RAEB 25, CMML 2) and 43 patients with SAA. Monosomy 7/del(7q) was present in 17 patients (RC 6, JMML 3, RAEB 8). Analyzed parameters were as follows: B cells, CD10+CD19+, CD19+45dim/neg, CD19+34+, CD19/CD34 ratio, CD34+, CD117 cells, CD34+38dim/neg, CD3+, CD3+4+, CD3+8+, CD3+HLADR+. Statistics We analyzed all parameters using non parametric tests (Mann-Whitney, Kruskal Wallis) and principal component analysis (PCA). Results Principal component analysis of all analyzed patients together clearly separates advanced forms of MDS from RC and SAA, the most contributing factor being the number of CD34 and CD117+ cells. In non parametric statistics following factors significantly differ among MDS subtypes and SAA (Kruskal-Wallis): CD19, CD117, CD34, CD3, CD3+4+, CD8+ and CD3+HLADR+. RC and SAA patients are separated mainly by the number of B cells and the CD34:CD19 ratio. In addition, the following parameters differ between RC and SAA (Mann-Whitney): CD34, CD117 and CD3+HLADR+. Unlike the CD34:CD19 ratio, the number of CD19+34+ precursors does not differ between RC and SAA patients. Patients with monosomy 7 do not differ from the remaining patients when all MDS patients are analyzed together or separately in the respective subgroups (RC, non RC, JMML) by PCA or by non parametric statistics. Conclusion PCA separates advanced MDS forms from RC and SAA. Advanced forms of MDS are characterized by increased percentage of CD34+ and CD117+ cells compared to RC and SAA patients. The global reduction of B cell progenitor compartment is pronounced especially in non-JMML cases of MDS, whereas SAA patients typically present with isolated reduction of cells at early stages (CD19+34+) of B cell development. Patients with monosomy 7 cluster within the respective disease category, they do not form own cluster in PCA. Supported by MSMT VZ MSM0021620813, MZO 00064203 VZ FNM, MZO VFN2005, IGA NR/9531-3, NPV 2B06064. Disclosures: No relevant conflicts of interest to declare.

Abstract 4980 Background Myeloproliferative disorders (MPD) in general result from proliferation of a clone of myeloid cells derived from a neoplastic pluripotent precursor or from connective tissue elements in bone marrow. This leads to increased numbers in one or more blood cell lines in peripheral blood. Some MPDs can be associated with thrombocytosis (MPD-T): essential thrombocythaemia (ET), polycythaemia vera (PV) and early stages of chronic idiopathic myelofibrosis (CIMF). Usually in MPD-T the thrombocytosis is caused by increased platelet production from proliferating mature megakaryocytes, especially in ET. Elevated platelet counts in these patients are often associated with both thromboembolic events and bleeding. One of the goals of MPD treatment is the control of platelet count. Immature platelets mirror the platelet production in bone marrow. In certain automated blood count analyzers it is possible to measure Immature platelet fraction (IPF) from the routine CBC samples sent to haematology lab. Reference range for IPF parameter for method used in this study is 1,1-6,1%. Objective Measurement of IPF parameter by fully automated analyzer (XE-2100, Sysmex, Kobe, Japan) in optical channel and analyzing it ( software IPF Master) in patients treated for Ph-negative MPD. We enrolled 85 pts- 67 ET (79%), 10PV(12%) and 8 CIMF (9%) patients; 57 were women and 28 men; median age 56 years ranging from 20 up to 83 years. We analyzed and evaluated IPF in whole group as well as in subgroups depending on diagnosis, gender, age, JAK-2 mutation and platelet count. Results At the time of assessment the majority of our pts were already commenced on treatment for their MPD. Platelet counts (plt) in whole cohort ranged from 164 up to 2148 ×109/l, with median 374 ×109/l. Thirty eight pts (45%) had plt < 350 ×109/l. Plt Conclusions MPD-T patients in our cohort did not have marked elevation of IPF parameter, neither those with high platelet counts (so far untreated pts). Thus we can speculate, that increased number of Plts in peripheral blood is caused by increased number of mature megacaryocytes in bone marrow which produce adequate numbers of platelets without increase of immature fraction rather than increased number of immature platelets released from megacaryocytes appearing in normal numbers in bone marrow Thus it seems that negative feedback of increased Plt counts on releasing of Plts from megacaryocytes is maintained also in patients with MPD-T. Further assessment is needed and should further determine, what is the clinical relevance (if any) of measurement of IPF in patients treated for MPD-T. Disclosures Blatny: Sysmex, Czech Republic: Consultancy.

Background: In recent years, recombinant factor VIIa (rFVIIa) has been used in non-hemophilia bleeding situations (factor VII deficiency, trauma, liver disease, uremia, surgical bleeding, platelet disorders, and intracranial hemorrhage) for achievement of hemostasis. Although, the risk of thrombosis in hemophilia patients with inhibitors receiving rFVIIa is quite low, its use in other clinical situations has been complicated by some reports of thrombotic events. Recently, rFVIIa has been used to treat coagulopathic and/or bleeding neonates with good success. However, the prevalence of thrombotic events in these neonates is completely unknown. This study was initiated to determine the risk of thrombotic events associated with rFVIIa use in neonates. Methods: We reviewed all published literature in neonates receiving rFVIIa. In addition, we reviewed all data submitted to the SeveN Bleep Registry, a database developed by the scientific standardization subcommittee on pediatric and neonatal hemostasis of the International Society on Thrombosis and Haemostasis (ISTH) to record all uses of rFVIIa in pediatric non-hemophilic patients. As the baseline prevalence of thrombosis for bleeding and/or coagulopathic neonates is also unknown, we also reviewed the records of 100 consecutive neonates from a single institution who received fresh frozen plasma (FFP) alone to treat their coagulopathy and/or bleeding. Results: A total of 98 non-hemophilic neonates received rFVIIa. The majority of these neonates received rFVIIa only after failing to achieve hemostasis with standard care (FFP, cryoprecipitate, platelet transfusions). Of those receiving rFVIIa, 7 had a thrombotic event reported. In the control group that received FFP alone, 7 neonates also suffered a thrombotic event. Although the risk of thrombosis in these two groups is similar, neonates receiving rFVIIa tended to have indwelling line related thrombosis, while those receiving FFP tended to have strokes or myocardial insults. Overall the prevalence of thrombotic events in bleeding and/or coagulopathic neonates appears to be 7%, whether or not they received rFVIIa. Conclusions: In this study, the overall prevalence of thrombotic events was similar in the rFVIIa and FFP group. As data for this study was collected in a retrospective manor, and thereby subject to publication and submission bias, a more accurate determination of the prevalence of thrombosis in neonates will require a prospective study.

Incidence of the thrombosis is age dependent with the lowest risk is in the childhood. Children mostly suffer from vein thrombosis (DVT/PE). Occurrence of thrombosis in children is 0,07/10 000, among hospitalized children is higher 3,5/10 000. In comparison with adults, these numbers are very low. LMWH is preferred in the treatment of DVT in children. UFH is used as second choice medication. LMWH is widely used in prevention of recurrence of DVT and sometimes it substitutes (especially in very young children) vitamin K antagonists. The most frequent form of application of LMWH is via subcutaneous injection. A few articles can be found in literature about treatment by intravenous continuous infusion in infants and in several cases in older children. The treatment by continuous infusion has certain advantages, especially for hospitalized patient with permanent i.v. access (painless, shorter half-life consecutively lower risk of bleeding, easier control). We present group of 27 children with DVT, who were treated with LMWH for first thrombosis from 2003 till 2005. We did the screening of thrombophilia in all of those children. We found FVleiden heterozygous in 38,1%, FII G2021OA heterozygous in 4,76, inherited deficiency of AT in 14,29%, BCP in 9,52 % and CVL was inserted in 52,38% of our patients.All patients had at least one of the risk factors of thrombophilia. We started to treat all patients with LMWH and the dose was adjusted to reach the level of antiXa between 0,5–1 IU/ml. We treated 6 patients (22,22%) by subcutaneous injection (average LMWH dose 215,54IU/kg/d) and 21 patients (77,78%) by continuous infusion (average dose 254,94IU/kg/d). Duration of the treatment was modified in accordance with the course of thrombosis (monitored by Doppler ultrasound with compression), but it went on for at least 7 days and was followed by the prophylaxis with LMWH or vitamin K antagonists. The treatment with LMWH (both i.v. or s.c.) lead to recanalisation of the vein in 26 cases (96,29%), 58% of them without any residue or mural thrombosis. We did not notice any bleeding as adverse event of the treatment in our patients.We would like to point out that treatment of DVT with continuous infusion of LMWH in children might be efficient and safe alternative of to s.c. application in certain circumstances. When administered by continuous infusion, LMWH has shorter half-life and it could be useful especially in hospitalized children and in children who are endangered by risk of bleeding complications.

Massive haemorrhage is a major cause of death in trauma patients. In military trauma cases the exsanquination is the reason of death in 44% (WDMET Vietnam war 1967–1969, 8000 casualties) In civilian trauma 39% of patients die because of massive haemorrhage. (Sauaia A et al. J. Trauma, 1995; 38:185–193). Massive bleeding is responsible for the death of more than 80% of trauma patients in the operating room (Hoyt DB et al. J. Trauma; 37: 426–432). There are also other medical specialisations which are faced with the problem of massive haemorrhage. Pathogenesis of life threatening bleeding is a complex problem not only in trauma patient. It is influenced by dilution coagulopathy, acidosis and other metabolic changes, thrombocytopenia and functional disorders of platelets, hypothermia and others. In fact all these problems lead - by different ways - to the thrombin formation disorders. Ineffective or inappropriate formation of thrombin than leads to defective or even no clot formation. If we were able to re-establish the proper thrombin formation, we would be theoretically able to solve most problems caused by massive haemorrhage in our patients. This is the theoretical basis for the use of rFVIIa as a potentially universal haemostatic agent in life-threatening bleeding. As the activity of rFVIIa is limited on the surfaces containing TF and phosphatidylserine - compartment physiologically active in normal clot formation - treatment with rFVIIa is probably one of the most save and most physiological way of treatment for such a bleeding. To support the evidence for the treatment of life-threatening bleeding with rFVIIa we have designed the software which registers individual cases when rFVIIa has been administered to control massive haemorrhage. This powerful tool will be able to provide its users with multiple outcomes and presentations based on statistically significant data. We believe that UniSeven registry will be useful for both intensive care givers and patients and that it will help to save numbers of human lives. Our work presents the technological background of the registry as well as first output from the registry based on data from more than 100 patients treated with rFVIIa mainly for life-threatening bleeding as a complication of trauma, surgery, cardiac surgery and malignancy in Czech Republic in years 2001– 2003. Up to now rFVIIa was administered in 114 cases in patients aged 0–80 years whose bleeding was refractory to standard therapeutical measures and threatens the patients′ lives.In 28, 57% the reason for rFVIIa administration was bleeding in trauma, 10, 7% cardiac surgery, 1, 79% gynaecology/obstetrics, 0, 89% intracranial haemorrhage and in 58% other reasons for uncontrolled bleeding. In 17 cases (15, 04%) rFVIIa was administered as a prophylaxis and in 96 cases (84, 9%) for treatment of life-threatening bleeding. Median dose of rFVIIa when administered for treatment of uncontrolled bleeding was 100 ug/kg and 1–2 doses was sufficient to treat the bleeding in more than 80% of cases. Such a treatment led to decrease of Packed cells transfusions from 7, 5 TU (median 24 h prior to rFVIIa administration) to 2 TU (median 24 h post rFVIIa administration). In our hands 62, 5% of patients with life threatening bleeding treated with rFVIIa survived. No death was related to rFVIIa treatment and we did not notice any serious adverse event related to rFVIIa treatment

Abstract 5136 Introduction: Pro-thrombotic risk factors are associated with increased risk of thrombosis. Some of them are inherited, but clinical manifestation of thrombosis in childhood is rare. It is most likely to appear in the adulthood. When leading to thrombosis during childhood, risk factors must be either very strong (e. g. homozygous deficiency of natural coagulation inhibitors), or must act together with other, usually acquired factors. Aims: - To analyse data of children referred for thrombophilia screening to Thrombosis Haemostasis centre, Dpt. of Paediatric Haematology University Hospital Brno, Czech Republic in years 2005–09. - To specify the characteristics of that cohort and identify the reasons for referral. -To determine prevalence of respective risk factors (RF) in children within study cohort. -To analyse possible correlation between related RF findings (ProC Global and FV Leiden, Protein C, Protein S; homocystein and MTHFR C677T polymorphism). Methods: We have collected data of all consecutive children aged from 0 to 18 years referred to our out-patient clinic for assessment of inherited thrombophilia in years 2005–2009 for any reason. Data recorded for each patient were as follows: age, gender, reason for assessment, thrombotic event and its type (if applicable) and vascular anomalies. Laboratory examinations done: FV Leiden mutation, Prothrombin gene mutation G20210A, MTHFR C677T polymorphism, protein C, protein S and Antithrombin levels, coagulation activity of F VIII, ProC Global test, homocystein and lipoprotein (a) level. Data were statistically analyzed to reach the aims of the study. Results: Data of 849 Caucasian children aged 0–18 years were available for analysis, 475 girls (55. 9 %) and 374 boys (44. 1 %). Median age was 11 years at the time of referral, boys 10 years, girls 13 years. Reasons for thrombophilia screening were as follows: family history of thrombosis/thrombophilia (70. 6 %), vascular anomaly (10. 8 %), thrombotic event (8 %) and others (10. 6 %). Thrombophilia screening was in more than 70 % of children performed before 15 years of age. Thrombotic event has been recorded in 79 patients (9. 3 %), both arterial (37. 6 %) and venous (63. 3 %). Adolescent patients had significantly more thrombotic events than younger children. Most of them were venous thromboses. Ischemic strokes and other arterial events were relatively more frequent in younger children. Frequency of “positive” laboratory findings in the studied cohort were as follows: MTHFR 60. 3 %, positive ProC Global test findings 58. 1 %, FV Leiden (heterozygous)37 %, hyperlipoproteinemia (a) 28. 5 %, protein S deficiency 11. 3 %, high FVIII activity 9. 4 %, Prothrombin gene mutation (heterozygous) 7. 7 %, Antithrombin deficiency 2. 7 %, elevation of homocystein 1. 6 % and protein C deficiency 1 %. Findings have confirmed high sensitivity of ProC Global test to the pathology in protein C pathway, particularly to FV Leiden mutation (sensitivity 98. 4 %). There was no statistically significant relation between homocystein level and MTHFR polymorphism status. Prevalence of RF in study cohort was found to be similar to the literature data. Deficiencies of natural coagulation inhibitors (AT, PC and PS) were rare, pro-thrombotic mutations were more frequent. Data suggest, that role of inherited pro-thrombotic risk factors in the development of thrombotic event in children is not the major one. It is very likely, that more potent risk factors, often acquired ones, are often important for development of thrombotic event during childhood. Conclusions: In our centre, we assessed proximately 170 children referred for thrombophilia screening per year. The incidence is thus 8 children per 10000. During 2005–09the main reason for referral was positive family history, but children were often referred in younger age, than recommended. The evidence available to date suggests that it is neither necessary nor useful to examine asymptomatic children before they reach puberty. Finding of inherited thrombophilia, and thus possibility to use measures preventing eventual thrombotic event, are more important in adolescence and adulthood rather than in younger age. In children with thrombotic event, however, it is recommended to screen for inherited risks. Diagnosis and treatment of thrombotic event in children requires a specialised care and relevant expertise of the Paediatric Thrombosis Haemostasis centre. Disclosures: No relevant conflicts of interest to declare.