ALBERT

Beschreibung: Abstract 2977 Poster Board II-957 Background: Venous thrombosis is a multifactorial disease and inherited genetic traits (IT) constitute a major risk factor. The aim of the present prospective cohort study was to determine i) the relative and absolute risks of first symptomatic thromboembolism [TE] in previously healthy family members of children with venous thromboembolism, and ii) whether to screen family members in a high risk population. Methods: In 205 patients (neonate to 18 years) and 526 FM followed over a total person-time of 14157 years /1000 units [person-time] a comprehensive IT screening was performed along with recording of family histories of preexisting cardiovascular diseases. FM were followed until July 2009: study endpoint was cumulative time to first TE within FM. Survival analysis (Cox regression: hazard ratio (HR/95% Confidence intervals (CIs)] adjusted for age and gender and number of new cases divided by the total population at risk (incidence rate) were calculated (events (%) per 1000 person-years [CIs]). Results: The final study population included 526 FM with 462 subjects 〉 14 years. The cumulative TE –free survival in FM with IT was significantly lower compared to those without: HR/CI: 6.6/ 3.3-13.5. The overall rate of symptomatic TEs was 2.9%[2.07-3.9]. The hazard adjusted for age and gender in the group of antithrombin(AT)-/protein C[PC)-/protein S(PS)-deficient FM was 29.4%[13.3-62.5], and for carriers of factor (F) V G1691A, F II G202010A mutations or elevated lipoprotein (a) it was found to be 3.3%[1.3-8.3], 1.96% [0.4- 9.0] and 2.1%[1.04-3.8]. Corresponding annual incidence rates in FM 〉 14 years were 4.8% for AT-/PC- or PS-deficiency states, 0.72% in subjects carrying the FV mutation, 0.36 % in FII carriers, and 0.20% for subjects with elevated lipoprotein (a) compared with 0.19% in FM with no IT. Thus, compared to adult data from the view of adult index cases [Lijfering W et al. Blood 2009] i) the risk of TE in family members of pediatric index cases with TE depends on IT, ii) the age at TE in the index patient as well as in the family members has a strong effect on TE incidence, and iii) the first symptomatic TE in primary healthy family members 〉 14 years of age with respect to the IT investigated is comparable to or exceeds adult data. Conclusions: i) Adult family members of pediatric index patients with an early onset of symptomatic thrombosis should be considered for IT testing, ii) primary thromboprophylaxis in family members derived from pediatric index patients should be considered in risk situations in adult carriers of AT/PC/PS-deficiencies & FV mutation. In addition, iii) larger prospective studies are needed to investigate the effects of multiple ITs and its interactions to take into account whether events are provoked or not to investigate the effect of screening. Disclosures: Off Label Use: Enoxaparin (LMWH) is used off-label in children to prevent symptomatic thromboembolism.

Beschreibung: To clarify the role of protein Z (PZ) in children with stroke/thromboembolism (TE), the present haplotype (HT)–based family study was performed. We genotyped 365 pediatric stroke/TE families (stroke n = 216; TE n = 149) for 4 single nucleotide polymorphisms (SNPs; rs3024718, rs3024731, rs3024772, and rs3024778) to assess the association between genetic variation within a conserved block of linkage disequilibrium harboring the PZ gene and pediatric TE. Association was assessed with use of the transmission disequilibrium test (TDT), corrected for multiple testing (permutation testing: HAPLOVIEW). In addition, PZ antigen was determined and correlated with carriership of PZ haplotypes and the FV G1691A mutation. Rs3024718, rs3024731, and rs3024772 are in tight linkage disequilibrium (LD) and define 4 haplotypes, capturing 97% of the genetic variation for this LD block. HT1 (ATG) was significantly overtransmitted from parents to affected offspring (HT frequency 73.5%, T:U 122:80, χ2 = 8.791, P = .003). The ATG risk haplotype was significantly correlated with greater PZ antigen levels. Multivariate analysis adjusted for age, sex, established thrombophilias, smoking, fibrinogen, and PZ levels revealed a significant association of the ATG haplotype and TE in children (odds ratio [OR] 1.4; 95% confidence interval [95% CI] 1.08-1.93). Our results suggest that the ATG haplotype of the PZ gene is a genetic marker for symptomatic TE in white German children.

Beschreibung: Background: Fibrinogen, the precursor of fibrin, is an essential component of the hemostatic system. A previous large case-control study showed that genetic variation in the fibrinogen gamma gene (FGG) increased the risk for VT in adults. We investigated the association of haplotypes comprising the fibrinogen alpha (FGA) and gamma (FGG) genes, carriership of the Factor VLeiden-mutation and risk for VT in two large family-based study samples for pediatric thromboembolism. Methods: We genotyped 7 single nucleotide polymorphisms in FGA and FGG, and the G1691A Factor VLeiden polymorphism in 244 pediatric VT and 268 thrombo-embolic stroke families. Association was assessed using the Transmission Disequilibrium Test (TDT) and corrected for multiple testing. Results: Association analysis revealed that the FGA-H1 haplotype, and the FGG-H2 and -H3 haplotypes, were significantly associated with VT (FGA-H1, P=0.05; FGG: H2, P=0.032; H3, P=0.0216). In an independent study sample, FGA-H1 (P=0.0085) and FGG-H2 (P=0.05) were significantly associated with TS. When stratifying for FVLeiden carriership, the association between FGA and FGG and VT was more pronounced in FVLeiden-negative families (FGA-H1, P=0.0006; FGG-H2, P=0.0005). Homozygous carriership of the FGG-H2 risk haplotype resulted in the lowest fibrinogen γ′ content (γ′ levels: 22.7±13.7 vs. 26.8±12.0, P=0.013; % γ′: 7.63±3.05 vs. 9.46±3.17, P=2.3×10−5), with increasing concentrations of fibrinogen γ′ in heterozygote H2 carriers. Compound heterozygote carriers of one FGG-H2 risk and one FGG-H3 protective haplotype, showed significant increase in fibrinogen γ′ (P=0.000032), while fibrinogen levels remained unchanged. In contrast, homozygote carriers of the protective FGG-H3 haplotype showed the highest concentration of fibrinogen γ′ content (% γ′: 9.21±3.09, P=0.0031) with decreased total fibrinogen levels. Conclusion: Our results support an important role of genetic variants in FGA and FGG in thromboembolism in children and adults. Our data further suggest that the genetic architecture of VT is complex and involves subtle influences through susceptibility and protective haplotypes in FGG and a genetic interaction with the FVLeiden-mutation.

Beschreibung: Abstract 805 Background: The interaction of von Willebrand factor [VWF] and its cleaving protease ADAMTS13 for preventing thrombosis in the microvasculature has been well described in patients with thrombotic thrombocytopenic purpura [TTP]. Recently it has been hypothesized that ADAMTS13 may protect the brain from ischemia by regulating VWF-platelet interaction after reperfusion, and that lower levels are associated with cardiovascular disease in young adults. Pediatric stroke is known as a multifactorial disease: Apart from various underlying mechanisms inherited genetic traits and intra-arterial thrombus formation constitute as major risk factors. The aim of the present nested case-control study was to determine the role of reduced ADAMTS13 levels in pediatric stroke. Methods: 208 pediatric patients with confirmed stroke (6 months to 18 years) and 128 population-based control children were investigated. Patients with liver disease, sepsis or antiphospholipid antibodies were excluded. ADAMTS13 activity [AC] and antigen [Ag] levels [kit: Technoclone, Vienna, Austria] have been evaluated 6 to 12 months after first stroke onset. Non-parametric statistics was performed for descriptive analysis [median (min-max) values] and inter-group comparisons [Mann-Whitney U test]. Correlation analysis was performed using Spearman rank correlation analysis. A p-value

Beschreibung: Background: Fibrinogen, the precursor of fibrin, is an essential component of the hemostatic system. A previous large case-control study showed that genetic variation in the fibrinogen gamma gene (FGG) increased the risk for VT in adults. Here we investigated the association of haplotypes comprising the fibrinogen alpha (FGA) and gamma (FGG) genes, carriership of the Factor V Leiden mutation and risk for VT in a large family-based study sample for pediatric VT. Methods: We genotyped 188 pediatric VT families for seven single nucleotide polymorphisms (SNPs) (rs6050, rs2070016, rs2070014 and rs2070011, rs1049636, rs2066861, rs2066860) as well as the G1691A Factor V Leiden (FV) polymorphism. Association was assessed using the Transmission Disequilibrium Test (TDT) and corrected for multiple testing using permutation testing as implemented in HAPLOVIEW. Interaction between FV and FGA and FGG, respectively, was assessed by TDT in families stratified for presence or absence of the FV mutation in the affected child. Results: rs6050, rs2070016, rs2070014 and rs2070011 located in the FGA gene are in tight linkage disequilibrium (LD) and define 5 common haplotypes (HT) and are linked with the neighboring FGG gene (q= 0.91). rs1049636, rs2066861, rs2066860 located in FGG are in tight LD and define 4 HTs. HTs in both, FGA and FGG are significantly overtransmitted from parents to affected offspring (FGA: HT1 (AACT), HT frequency 0.32, T:U 62: 32, p=0.0025; FGG: HT2 (ATC), HT frequency 0.32, T:U 60:32, p=0.0035). When stratifying for FV status, it became apparent that the association between FGA and FGG and VT was more pronounced in FV-negative families (FGA, HT1, T:U 55:24, p=0.0006; FGG, HT2, T:U 55:24, p=0.0005), while absent in FV-positive families. Conclusion: Our results indicate that genetic variation in FGA and FGG are risk factors for VT in children, and further that an epistatic interaction between FGA/FGG and FV Leiden influences the risk of FGG and FGA on pediatric VT. Our study highlights the complex nature of VT and the necessity to evaluate gene-gene interactions in association studies of complex, polygenic diseases.

Beschreibung: Background and objectives: Earlier studies found a strong support for a genetic basis for regulation of coagulation factor levels. The present study was conducted to estimate the variation within coagulation factors levels, and how much of this variation could be attributed to heritability and household effect in pediatric stroke families. Methods: Blood samples were collected from 853 individuals from 224 white pediatric stroke pedigrees (male 51.3%). Heritability (h2r) and household effect (c2) were estimated for plasma concentrations of fibrinogen, factor (F) II, V, VIIIC, vWF, antithrombin, protein C, protein S, protein Z, prothrombin fragment F1.2 and D-dimer using the variance component method in sequential oligo-genetic linkage analysis routines (SOLAR). Results: When incorporating h2r and c2 in one model, high and significant h2r estimates were found for protein Z (31.7), protein S (27.5), fibrinogen 29.9) and von Willebrand factor (20.4). In addition to the significant h2r estimates c2 showed a significant effect on phenotypic variation for protein Z (26.0), protein S (22.2) and vWF (14.8). A significant household effect without h2r interaction was found for FVIIIC (30.7), FII (25.6), protein C and FV (12.0). Conclusion: In the cohort investigated we have shown that genetic factors have a major effect on plasma concentrations of coagulation factors. Our research stresses the importance of research into the genetic regulation of proteins involved in hemostasis associated with pediatric stroke.

Beschreibung: Previous case-control studies showed that genetic variation in the fibrinogen γ gene (FGG) increased the risk for deep vein thrombosis (VT) in adults. We investigated the association between the fibrinogen α (FGA) and FGG haplotypes, the factor VLeiden-mutation, and pediatric VT and thromboembolic stroke (TS) in 2 independent study samples. Association analysis revealed that the FGA-H1 and FGG-H2 haplotypes were significantly overtransmitted to VT patients (FGA-H1, P = .05; FGG: H2, P = .032). In contrast, the FGG-H3 haplotype was undertransmitted (P = .022). In an independent study sample, FGA-H1 (P = .008) and FGG-H2 (P = .05) were significantly associated with TS. The association of FGA and FGG haplotypes with VT was more pronounced in FVLeiden-negative families (FGA-H1, P = .001; FGG-H2, P = .001), indicating a genetic interaction between both risk factors. The risk-conferring FGG-H2 and the protective FGG-H3 haplotypes correlated with low (FGG-H2) and high (FGG-H3) levels of the γ′ chain variant, respectively. These results provide independent and novel evidence that FGA-H1 and FGG-H2 variants are associated with an increased risk of VT and TS in children. The observed negative correlation of genetic VT risk with the plasma levels of the fibrinogen γ′ variant suggests that FGG-H2 and -H3 haplotypes modify thrombosis risk by controlling the level of this FGG splice isoform.