ALBERT

Description: Key Points Hermansky-Pudlak syndrome type 2 confers a moderate risk for hemophagocytic lymphohistiocytosis.

Description: The present study was designed to evaluate prothrombotic risk profiles in 59 consecutively recruited white neonates with renal venous thrombosis (RVT). The rates of prothrombotic risk factors (PRs)—for example, the factor V (FV) 1691G〉 A mutation, the factor II (FII) 20210G〉 A variant, antithrombin (AT), protein C (PC), protein S (PS), elevated lipoprotein(a) (Lp(a)), total fasting plasma homocysteine (tHcy) levels, and anticardiolipin antibodies (ACAs)—were compared with those of 118 healthy control children. At onset, 32 (54.2%) of the 59 neonates showed underlying clinical conditions; 40 (67.8%) of them and 23 (85.2%) of the 27 infants with idiopathic RVT showed at least one PR. Univariate analysis revealed significantly elevated odds ratios/95% confidence intervals (ORs/95% CIs) for FV and Lp(a). Additionally, PC/AT deficiency and ACAs were found significantly more often in the patient group (P = .04). Multivariate analysis calculated significant ORs/95% CIs only for FV (OR, 9.4; 95% CI, 3.3-26.6) and elevated Lp(a) (OR, 7.6; 95% CI, 2.4-23.8). Of the 59 neonates investigated, 53 revealed renal atrophy, and 13 children additionally suffered from severe arterial hypertension. In conclusion, the present study demonstrates the significance of genetic PR—especially the FV mutation and elevated Lp(a)—for the etiology of neonatal RVT.

Description: Pediatric stroke is a rare but highly penetrant disease with a strong genetic background. Although there are an increasing number of genome-wide association studies (GWASs) for stroke in adults, such studies for stroke of pediatric onset are lacking. Here we report the results of the first GWAS on pediatric stroke using a large cohort of 270 family-based trios. GWAS was performed using the Illumina 370 CNV single nucleotide polymorphisms array and analyzed using the transmission disequilibrium test as implemented in PLINK. An enrichment analysis was performed to identify additional true association signals among lower P value signals and searched for cumulatively associated genes within protein interaction data using dmGWAS. We observed clustering of association signals in 4 genes belonging to one family of metalloproteinases at high (ADAMTS12, P = 2.9 × 10−6; ADAMTS2, P = 8.0 × 10−6) and moderate (ADAMTS13, P = 9.3 × 10−4; ADAMTS17, P = 8.5 × 10−4) significance levels. Over-representation and gene-network analyses highlight the importance of the extracellular matrix in conjunction with members of the phosphoinositide and calcium signaling pathways in the susceptibility for pediatric stroke. Associated extracellular matrix components, such as ADAMTS proteins, in combination with misbalanced coagulation signals as unveiled by gene network analysis suggest a major role of postnatal vascular injury with subsequent thrombus formation as the leading cause of pediatric stroke.

Description: It has been recently shown that the first bleeding onset in children with severe hemophilia A (HA) carrying prothrombotic risk factors is significantly later in life than in non-carriers.1 The present multicenter study was performed to determine whether the factor (F) V G1691A or the F II G20210A are associated with decreased annual bleeding episodes (ABE) in 106 pediatric PUP patients with severe HA (Intron 22 58.6%) consecutively admitted to German pediatric hemophilia treatment centers. Treatment was initiated according to the frequency of bleedings, and most patients received on demand therapy with a switch over to prophylactic therapy 3x/week (40–60 IU/kgKG factor VIIII concentrate) when more than three bleedings (range 2–6) had occurred into the same joint (n=49). Prospective median(range) patient follow-up was 14(4–35) years. Heterozygosity of the FV mutation was found in 8 subjects, homozygosity in one, and 5 children carried the FII mutation once combined with protein C-deficiency. Carriers of the FV and FII mutations had significantly fewer ABE than non-carriers (p=0.004). 66 of 106 PUP patients developed at least one target joint with a median(range) Pettersson score of 1(0–12) available in 57 patients clearly dependent on age (p=0.039) as well as ABE (p=0.037). The “Nuss” joint score available in 33 subjects highly correlated with the Pettersson score (p=0.007). Data presented here give evidence that the clinical expression of severe HA in children is influenced by the co-expression of the FV and FII mutation.

Description: Abstract 3154 Poster Board III-91 Background. The development of alloantibodies that inhibit the coagulant activity of factor VIII (FVIII) is currently the most challenging complication of treatment in persons with hemophilia. Among other factors known to influence inhibitor development, several reports in the literature claimed for a different rate of inhibitor development in hemophilia A (HA) patients after plasma derived (pd-) or recombinant (r-) FVIII administration. Aim of this study was to compare the incident rate of inhibitors in HA patients treated with pd- or r-FVIII through systematic appraisal of the literature. Methods Studies reporting data about inhibitor rate in previously untreated patients (PUPs) with severe (〈 0.01 UI/mL) or severe-moderate HA were searched in the following electronic databases: Medline, EMBASE, OVID, Web of Science, The Cochrane Library. Details about study and patient characteristics were abstracted. To avoid double counting of patients included in more than one report of the same authors/working groups, patient recruitment periods and catchment areas were evaluated and authors were contacted for clarification if needed. If any of the required data could not be found in the published report, the corresponding author was contacted to provide the missing data of interest. High responder (HR) inhibitors were defined as 〉=5 BU/mL. Inhibitors were defined as transient when spontaneously disappearing within 6 months without the need to change treatment regimen. Firstly, the incident rate of inhibitor was recalculated for each study as the number of new inhibitor cases during the observation period divided by the number of HA patients initially inhibitor-free. Secondly, the recalculated rates were pooled for pd- and r- treated cohorts with the random effect model of Laird and Mosteller for single-cohort studies. Thirdly, a summary rate ratio (RR) was calculated for the subset of studies reporting parallel cohorts of patients treated with pd- or r-FVIII concentrates using fixed-effects and random-effects models. Sensitivity analysis, meta-regression and multivariate ANOVA were used to investigate the effect of covariates. Heterogeneity across studies and publication bias were evaluated. Results Twenty-four trials were included (19 prospective), 21 of which reporting details on HR inhibitors for a total of 2113 patients (1170 treated exclusively with pd-, 943 with r-FVIII; 1143 were severe), median age at enrolment was 9.6 months. The total number of inhibitors was 389 of which 135 in patients treated with pd- and 254 in patients treated with r-FVIII. HR inhibitors were 256 (103 for pd- and 153 for r-FVIII). Non-transient inhibitors were 162 (59 for pd- and 103 for r-FVIII). Inhibitor testing was from every 5 exposure days to every 2 year. Pooled incident rate (95% CI) was in all trials 14.7 (10.7 to 19.9) for pd- and 26.6 (22.6 to 31.0) for r-; for prospective trials 9.5 (5.7 to 15.3) for pd- and 22.4 (17.1 to 28.3) for r-; for HR inhibitors 8.5 (4.8 to 14.6) for pd- and 15.4 (12.2 to 19.3) for r-; for non-transient inhibitors 12.7 (7.3 to 21.1) for pd- and 18.9 (14.3 to 24.6) for r-. Six non concurrent cohort studies including 1259 HA patients met the inclusion criteria for RR calculation. Compared to pd-FVIII a statistically significant association with inhibitor development was demonstrated for r-FVIII, with summary RR ranging (95% CI) for HR inhibitors of 1.7 (C.I. 1.3 to 2.7), p〈 0.001, I2 = 0%, Harbord-Egger bias indicator p=0.07, fixed effect model; for all inhibitor patients of 2.0 (1.5 to 2.6), p〈 0.001, I2 = 41.6%, Harbord-Egger bias indicator p=0.06, random effect model. In the complete study set, testing frequency and study period correlated with rate of inhibitors development at meta-regression. At multivariate ANOVA testing frequency and study period were the strongest determinants of inhibitor development, and type of concentrate lost its statistical significance in the complete model. Conclusions This systematic review suggests that a lower inhibitor rate is found in patients with severe HA with the use of pd-FVIII, but also underscores the critical role of study related characteristics in the evaluation of the true effect of source of factor VIII. Future randomized and prospective follow-up studies are warranted. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 221 Introduction: Today, the most problematic and costly complication of the treatment of hemophilia A that remains to be overcome is the development of inhibitory antibodies (FVIII inhibitors) to FVIII replacement therapy, particularly in previously untreated patients (PUPs). Aim of the study: The highest risk of developing inhibitors to FVIII is during the first 20 exposure days (EDs). If the patient can be brought through this high risk period without inhibitor development, the subsequent risk is low. We therefore, as a pilot project, developed a prophylaxis regimen for the first 20–50 EDs specifically designed to induce tolerance to the administered FVIII and to minimize inhibitor development. Patients and Methods: Twenty-six consecutive PUPs with severe hemophilia A (

Description: Background: Venous thromboembolism [TE] is a multifactorial disease and antithrombin [ATD]-, protein C [PCD]- or protein S [PSD]-deficiency constitutes a major risk factor. Since screening for thrombophilia is controversial, individuals at high risk for recurrence who benefit from screening need to be identified. Primary study objective was to determinethe individual recurrence risk in children compared to adults with TE with respect to their thrombophilia status. Methods: In 142 consecutively enrolled TE patients (children n=85; adults n=57) with ATD, PCD or PSD after exclusion of six children with purpura fulminans due to homozygous PCD or PSD we calculated i) the cumulative recurrence rates (CRR) at 1, 5 and 10 year following the first TE onset and, ii) in addition, the absolute recurrence risk (ARR) per 100 patient years (%). Results: At first TE onset in univariate analysis a higher rate of unprovoked TE was found in children, whereas adults presented with a higher rate of a positive TE family history and a higher rate of recurrence: 40 out of 136 patients showed a second TE after withdrawal of anticoagulation (AC) or insufficient AC [n=6]. Two events in children were fatal [pulmonary embolism]. The overall CRR at 1, 5 and 10 years was 10.9%, 20.4% and 29.2% with total ARR [95% CIs] of 5.3 [3.4-7.8] in adults compared to 2.1 [1.0-5.3] in children [p=0.004]. Whereas the ARR was no different between adults and children in ATD patients [5.1 versus 4.7; p=0.85] and in symptomatic PCD subjects [3.9 versus 1.6; p=0.17], adults with PSD showed a higher ARR compared to children [6.3 versus 0.1; p=0.001]. Positive family TE history did not predict recurrence. Conclusion: Given the high ARR of 5.3% in adults and 2.1% in children we suggest screening for ATD, PCD and PSD in adult and pediatric TE patients. The high rate of ARR should be taken into account when initiating future therapeutic trials. Duration and intensity of AC should be carefully reevaluated in patients with ATD, PCD or PSD. Disclosures Young: Baxter, Grifols: Consultancy, Honoraria. Nowak-Gottl:Bayer, LFB: Membership on an entity's Board of Directors or advisory committees.

Description: Background: Venous thromboembolism [TE] is a multifactorial disease and antithrombin [ATD] -, protein C [PCD] - or protein S [PSD] -deficiency constitutes a major risk factor. The objective of the present study was to i) evaluate the prevalence of ATD, PCD and PSD in a white Israeli-German cohort of children with TE, ii) the underlying gene mutations, and iii) the clinical presentation of ATD, PCD and PCS on symptomatic TE in children. Methods: In 367 unselected children (0.1-18 years) with TE recruited between July 1996 and December 2013 from Germany & Israel, a comprehensive thrombophilia screening was performed. Along with standardized plasma-based coagulation assays and the use of age-dependent reference values ATD, PCD and PSD were confirmed by family studies and/or molecular diagnosis [gene sequencing & multiplex ligation-dependent probe amplification]. Apart from descriptive analysis non-parametric statistics was performed. To compare the rates of deficiency phenotypes, locations of TE, spontaneous versus provoked TE, presence or absence of a positive family history of TE, Chi-square or Fisher’s exact test was applied. Results: 6.6% of children were ATD, 6.8% PCD including purpura fulminans (1.4%) and 8.2% patients carried PSD. Mean age at first TE was 13 years (range 0.1 to 18) with no statistically significant difference found between deficiency phenotypes (p=0.32). 38 children were male. 72 of 76 children (95%) showed type 1 deficiency, whereas in 4 cases [ATD] a type 2 deficiency was found (p=0.004). Underlying gene mutations were in the majority of cases missense mutations (SERPINC1: 75%; PROC: 93%; PROS1: 72%), with 24% presence of the Herleen polymorphism (CM951058) in children with PSD. Homozygous genotypes were found in 4 cases [ATD], 6 cases [PCD] and in one PSD carrier [p=0.07]. ATD co-occurred with the factor 5 mutation [F5] at rs6025 in one and the factor 2 susceptibility variant [F2] at rs1799963 in two children. PSD co-occurred with the F5 or the homozygous F2 in one case each. Apart from purpura fulminans which was seen only in neonates with homozygous PCD, thrombotic locations were similarly distributed (p=0.11): multiple veins (n=7), cerebral veins/stroke of venous origin (n=18), deep veins [DVT; n=38], DVT & pulmonary embolism (n=13). The rates of provoked TE were 57% [ATD], 48% [PCD] and 60% in PCD (p=0.06). A positive family history was present in 43% [ATD], 40% [PCD] and 57% [PSD; p=0.41]. After withdrawal of anticoagulation, - performed on an individual basis according to CHEST guidelines (updated according to year of publication) -, recurrence rates were 38% [ATD], 24% [PCD] and 6.6% in carriers of PSD (p=0.017). Conclusion: Given its clinical implication for patients and family members, thrombophilia testing should be performed and the benefit of medical or educational interventions should be evaluated in this high risk population Disclosures No relevant conflicts of interest to declare.

Description: Abstract 1303 Poster Board I-325 Background A number of environmental and genetic factors have been identified to influence inhibitor development in children with severe hemophilia A (HA): among them, individual therapeutic regimens and the use of different factor VIII products have been controversially discussed. Methods In the present multicenter cohort study we evaluated the impact of i) treatment intensity [median individual dose administered during the first 6 to 8 weeks] and ii) type of factor VIII product [plasma-derived (pd); recombinant-derived (r)] on the risk of high-titre inhibitor development in 150 previously untreated patients with severe hemophilia A (HA) consecutively ascertained between 1982 and 2007 from five German catchment areas. Patients were followed over a period of 200 exposure days from HA onset. Study endpoint was inhibitor-free survival time related to treatment with adjustment for treatment period. Plasma levels of factor VIII were determined by one-stage clotting assays. Inhibitor testing was performed at least monthly to 3 monthly when on therapy using the Bethesda method or its modification [Nijmegen]: The lower detection limit was set at 0.6 Bethesda units [BU]. A peak inhibitor titer of 〉 5 BU was defined as high responder [HR]. A positive inhibitor testing was stated when an inhibitor was measured at least in two independent follow-up visits. The cumulative inhibitor-free survival was calculated using multivariate Cox regression [hazard ratio (HR) and 95% confidence intervals [CIs]]. Results During the follow-up period 30 of 150 children (20.0%) developed a high titre inhibitor. In univariate analysis the median dose increase per IU/kgbw significantly increased the hazard towards HR inhibitor development [HR/CI: 1.08/1.05-1.11]. In addition, 14 of 52 children treated with rFVIII concentrates (27%) versus 16 of 98 children (16.3%) treated with pdFVIII concentrates developed HR during the observation period [HR/CI: 1.9/0.9-3.9]. In multivariate analysis treatment intensity adjusted for FVIII products and treatment period were independently associated with the development of clinical meaningful inhibitors [HR/95%CI: 1.08/1.1-1.1]. Conclusion Data presented here support the hypothesis that clinical meaningful inhibitor development is of multifactorial origin and that treatment intensity plays a major role. Disclosures Off Label Use: Enoxaparin (LMWH) is used off-label in children to prevent symptomatic thromboembolism.