Safety of intramuscular COVID-19 vaccination in patients with haemophilia.

BACKGROUND: Guidelines recommend that patients with haemophilia should preferably receive vaccination subcutaneously. COVID-19 and other vaccines, however, are only licenced for intramuscular application. AIMS: To assess the safety of intramuscular COVID-19 vaccination in patients living with haemophilia. METHODS: Part A of this prospective observational study enrolled consecutive patients with haemophilia A (HA) and B (HB) of all ages and severities and assessed injection site bleeding and other complications within 30 days of vaccination. Part B enrolled patients providing informed consent for detailed data collection including medication and prophylaxis around the time of vaccination. Logistic regression was performed to assess potential risk factors for bleeding. RESULTS: Four hundred and sixty-one patients were enrolled into part A. The primary endpoint injection site bleeding occurred in seven patients (1.5%, 95% confidence interval .7-3.1%). Comprehensive analysis of 214 patients (404 vaccinations, part B) revealed that 97% of patients with severe haemophilia had prophylaxis before vaccination, either as part of their routine prophylaxis or using additional doses. 56% and 30% of patients with moderate and mild haemophilia, respectively, received prophylaxis before vaccination. Among the seven bleeds recorded, three occurred when intramuscular vaccination was done without prophylaxis (odds ratio 12). CONCLUSIONS: This is the first prospective study reporting on the safety of intramuscular vaccination in haemophilia. The rate of injection site bleeding was low in mild haemophilia, and in moderate and severe haemophilia if patients received factor prophylaxis.

Rare genetic variants in SMAP1, B3GAT2, and RIMS1 contribute to pediatric venous thromboembolism.

Recent genome-wide association studies (GWAS) have confirmed known risk mutations for venous thromboembolism (VTE) and identified a number of novel susceptibility loci in adults. Here we present a GWAS in 212 nuclear families with pediatric VTE followed by targeted next-generation sequencing (NGS) to identify causative mutations contributing to the association. Three single nucleotide polymorphisms (SNPs) exceeded the threshold for genome-wide significance as determined by permutation testing using 100 000 bootstrap permutations (P < 10-5). These SNPs reside in a region on chromosome 6q13 comprising the genes small ARF GAP1 (SMAP1), an ARF6 guanosine triphosphatase-activating protein that functions in clathrin-dependent endocytosis, and ß-1,3-glucoronyltransferase 2 (B3GAT2), a member of the human natural killer 1 carbohydrate pathway. Rs1304029 and rs2748331 are associated with pediatric VTE with unpermuted/permuted values of P = 1.42 × 10-6/2.0 × 10-6 and P = 6.11 × 10-6/1.8 × 10-5, respectively. Rs2748331 was replicated (P = .00719) in an independent study sample coming from our GWAS on pediatric thromboembolic stroke (combined P = 7.88 × 10-7). Subsequent targeted NGS in 24 discordant sibling pairs identified 17 nonsynonymous coding variants, of which 1 located in SMAP1 and 3 in RIMS1, a member of the RIM family of active zone proteins, are predicted as damaging by Protein Variation Effect Analyzer and/or sorting intolerant from tolerant scores. Three SNPs curtly missed statistical significance in the transmission-disequilibrium test in the full cohort (rs112439957: P = .08326, SMAP1; rs767118962: P = .08326, RIMS1; and rs41265501: P = .05778, RIMS1). In conjunction, our data provide compelling evidence for SMAP1, B3GAT2, and RIMS1 as novel susceptibility loci for pediatric VTE and warrant future functional studies to unravel the underlying molecular mechanisms leading to VTE.

Impact of high-risk thrombophilia status on recurrence among children with a first non-central-venous-catheter-associated VTE: an observational multicentre cohort study.

Deficiency of antithrombin (AT), protein C (PC) or protein S (PS) constitutes a major risk factor for venous thromboembolism (VTE). Individuals at high risk for recurrence who benefit from screening need to be identified. The primary study objective was to determine the individual recurrence risk among children with a first non-central-venous-catheter-associated VTE with respect to their thrombophilia status and to evaluate if the clinical presentation at first VTE onset differs between children with AT, PC or PS deficiency versus no thrombophilia. We calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia, age, sex and positive family VTE history in 161 consecutively enrolled paediatric VTE patients. The presence of a deficiency relative to no thrombophilia was evaluated as a potential predictor of recurrence. Predictors for recurrence were AT deficiency (hazard ratio/95% CI: 6·5/2·46-17·2) and female gender (2·6/1·1-6·35). The annual recurrence rates (95% CIs) were 5·4% (2·6-10) in AT-deficient children, 1·3% (0·3-3·8) in patients with PC deficiency, 0·7% (0·08-2·4) in the PS-deficient cohort and 0·9% (0·4-1·8) in patients with no thrombophilia. Positive family VTE history or combined thrombophilias did not predict recurrence. Given the overall annual incidence rate of recurrence of 1·5% we suggest screening for AT deficiency in children with VTE.

Impact of high risk thrombophilia status on recurrence among children and adults with VTE: An observational multicenter cohort study.

BACKGROUND: Antithrombin [AT]-, protein C [PC]- or protein S [PS]-deficiency [D] constitutes a major risk factor for venous thromboembolism [VTE]. Primary study objective was to evaluate if the clinical presentation at first VTE onset differs between children and adults and to compare the individual recurrence risk among patients with respect to age at onset and their thrombophilia status ATD, PCD or PSD. METHODS/PATIENTS/RESULTS: In 137 of 688 consecutively enrolled pediatric and adult VTE patients we calculated the absolute risk of VTE recurrence and event-free-survival adjusted for thrombophilia and positive family VTE history. At first VTE children manifested i) with a lower rate of pulmonary embolism, ii) a higher rate of cerebral vascular events or multiple VTEs, and iii) showed a higher proportion of unprovoked VTE compared to adolescents and adults. Adult patients reported more often a positive VTE history compared to younger study participants. The adjusted odds of recurrence in adults was 2.05 compared to children. CONCLUSION: At disease manifestation children and adults differ with respect to i) thrombotic locations, ii) percentage of unprovoked versus provoked VTE, and iii) different rates of positive VTE family histories. Furthermore, adults showed a two-fold increase risk of VTE recurrence compared to children.

Clinical and laboratory characteristics of children with venous thromboembolism and protein C-deficiency: an observational Israeli-German cohort study.

Venous thromboembolism [TE] is a multifactorial disease and protein C deficiency [PCD] constitutes a major risk factor. In the present study the prevalence of PCD and the clinical presentation at TE onset, including neonatal purpura fulminans, in a cohort of children are reported. In 367 unselected children (0·1-19 years) recruited between July 1996 and December 2013, a comprehensive thrombophilia screening was performed along with recording of anamnestic data. Twenty-five of 338 children (7·4%) had PCD. Mean age at first TE onset was 10 years (range 0·1-18). Leading thromboembolic manifestations were neonatal purpura fulminans (n = 5), TE of cerebral veins (n = 3), stroke (n = 2) deep veinthrombosis (DVT) of the leg (n = 10), DVT & pulmonary embolism (n = 2) and DVT & pelvic veins (n = 3). Concomitant risk factors for TE were identified in 12 patients, whereas 13 children spontaneously developed TE. A positive family history of DVT was found in 10 children. In this unselected cohort of paediatric patients with symptomatic TE the overall prevalence of PCD was 7·4%; 1·5% presented with neonatal purpura fulminans. 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.

Inherited thrombophilia in children with venous thromboembolism and the familial risk of thromboembolism: an observational study.

Screening for inherited thrombophilia (IT) is controversial; persons at high risk for venous thromboembolism (VTE) who benefit from screening need to be identified. We tested 533 first- and second-degree relatives of 206 pediatric VTE patients for IT (antithrombin, protein C, protein S, factor V G1691A, factor II G20210A) and determined the incidence of symptomatic VTE relative to their IT status. The risk for VTE was significantly increased among family members with, versus without, IT (hazard ratio = 7.6; 95% confidence interval [CI], 4.0-14.5; P < .001) and highest among carriers of antithrombin, protein C, or protein S deficiency (hazard ratio = 25.7; 95% CI, 12.2-54.2; P < .001). Annual incidences of VTE were 2.82% (95% CI, 1.63%-4.80%) among family members found to be carriers of antithrombin, protein C, or protein S deficiency, 0.42% (0.12%-0.53%) for factor II G202010A, 0.25% (0.12%-0.53%) for factor V G1691A, and 0.10% (0.06%-0.17%) in relatives with no IT. Given the high absolute risk of VTE in relatives with protein C, protein S, and antithrombin deficiency, we suggest screening for these forms of hereditary thrombophilia in children with VTE and their relatives. Interventional studies are required to assess whether thromboembolism can be prevented in this high-risk population.

Validation of a predictive model for identifying an increased risk for thromboembolism in children with acute lymphoblastic leukemia: results of a multicenter cohort study.

Among risk factors for developing thromboembolism (VTE) in children with acute lymphoblastic leukemia were Escherichia coli asparaginase, concomitant steroid use, presence of central venous lines, and thrombophilic abnormalities. Developing a predictive model for determining children at increased risk would be beneficial in targeting interventional studies to high-risk groups (HRGs). Predictive variables were incorporated into a risk assessment model, which was evaluated in 456 children and then validated in 339 patients. VTE risk by score was no greater than 2.5 for low-risk group (LRG) and greater than 2.5 for HRG. VTE rates at 3.5 months (validation cohorts) were 2.5% in LRG and 64.7% in HRG. In multivariate analysis adjusted for age, duration of asparaginase administration, enoxaparin prophylaxis, and T-immunophenotype, the HRG was significantly associated with VTE compared with the LRG (hazard/95% confidence interval [CI], 8.22/1.85-36.53). Model specificity was 96.2% and sensitivity was 63.2%. As secondary objective we investigated the use of enoxaparin for VTE prophylaxis in the HRG. HRG patients without enoxaparin prophylaxis showed a significantly reduced thrombosis-free survival compared with children on low-molecular-weight heparin (LMWH). On the basis of the high specificity, the model may identify children with leukemia at risk of VTE. LMWH may help prevent VTE in the HRG; this warrants assessment in larger cooperative clinical trials.

Home therapy with intravenous human C1-inhibitor in children and adolescents with hereditary angioedema.

BACKGROUND: C1-esterase inhibitor (C1-INH) replacement therapy is the treatment of choice for acute edema attacks in patients with hereditary angioedema (HAE). STUDY DESIGN AND METHODS: Our retrospective, observational study assessed the efficacy and safety of home therapy with a human plasma-derived C1-INH concentrate (pC1-INH) in 20 pediatric patients with HAE who had previously been treated with physician-based therapy. While on home therapy, 15 patients received on-demand treatment and five received individual replacement treatment (IRT). RESULTS: The switch to home therapy did not involve a significant increase in the dose of pC1-INH administered, but there was a significant increase in dosing frequency. Although only two patients were affected, the frequency of laryngeal attacks appeared to decrease on home therapy. All attacks, including laryngeal edema, were treated successfully during home therapy with pC1-INH. The mean annual number of days hospitalized was reduced from 3.8 during physician-based therapy to 0.11 during home therapy. No side effects or injection site complications were reported. The median time from onset of attack to administration of pC1-INH was reduced from 67.5 minutes during physician-based therapy to 15 minutes after switching to home therapy. The corresponding median time to initial symptom relief for all types of attack was reduced from 60 to 40 minutes. CONCLUSION: As in adults, home therapy with pC1-INH is effective and safe in the treatment of HAE attacks in pediatric patients; a larger, randomized study should ideally confirm our findings before this approach can be considered the standard of care for pediatric patients.

Impact of thrombophilia on risk of arterial ischemic stroke or cerebral sinovenous thrombosis in neonates and children: a systematic review and meta-analysis of observational studies.

BACKGROUND: The aim of this study was to estimate the impact of thrombophilia on risk of first childhood stroke through a meta-analysis of published observational studies. METHODS AND RESULTS: A systematic search of electronic databases (Medline via PubMed, EMBASE, OVID, Web of Science, The Cochrane Library) for studies published from 1970 to 2009 was conducted. Data on year of publication, study design, country of origin, number of patients/control subjects, ethnicity, stroke type (arterial ischemic stroke [AIS], cerebral venous sinus thrombosis [CSVT]) were abstracted. Publication bias indicator and heterogeneity across studies were evaluated, and summary odds ratios (ORs) and 95% confidence intervals (CIs) were calculated with fixed-effects or random-effects models. Twenty-two of 185 references met inclusion criteria. Thus, 1764 patients (arterial ischemic stroke [AIS], 1526; cerebral sinus venous thrombosis [CSVT], 238) and 2799 control subjects (neonate to 18 years of age) were enrolled. No significant heterogeneity was discerned across studies, and no publication bias was detected. A statistically significant association with first stroke was demonstrated for each thrombophilia trait evaluated, with no difference found between AIS and CSVT. Summary ORs (fixed-effects model) were as follows: antithrombin deficiency, 7.06 (95% CI, 2.44 to 22.42); protein C deficiency, 8.76 (95% CI, 4.53 to 16.96); protein S deficiency, 3.20 (95% CI, 1.22 to 8.40), factor V G1691A, 3.26 (95% CI, 2.59 to 4.10); factor II G20210A, 2.43 (95% CI, 1.67 to 3.51); MTHFR C677T (AIS), 1.58 (95% CI, 1.20 to 2.08); antiphospholipid antibodies (AIS), 6.95 (95% CI, 3.67 to 13.14); elevated lipoprotein(a), 6.27 (95% CI, 4.52 to 8.69), and combined thrombophilias, 11.86 (95% CI, 5.93 to 23.73). In the 6 exclusively perinatal AIS studies, summary ORs were as follows: factor V, 3.56 (95% CI, 2.29 to 5.53); and factor II, 2.02 (95% CI, 1.02 to 3.99). CONCLUSIONS: The present meta-analysis indicates that thrombophilias serve as risk factors for incident stroke. However, the impact of thrombophilias on outcome and recurrence risk needs to be further investigated.

Consensus Recommendations for Intramuscular COVID-19 Vaccination in Patients with Hemophilia.

BACKGROUND: Currently available coronavirus disease 2019 (COVID-19) vaccines are approved for intramuscular injection and efficacy may not be ensured when given subcutaneously. For years, subcutaneous vaccination was recommended in patients with hemophilia to avoid intramuscular bleeds. Therefore, recommendations for the application of COVID-19 vaccines are needed. METHODS: The Delphi methodology was used to develop consensus recommendations. An initial list of recommendations was prepared by a steering committee and evaluated by 39 hemophilia experts. Consensus was defined as ≥75% agreement and strong consensus as ≥95% agreement, and agreement as a score ≥7 on a scale of 1 to 9. After four rounds, a final list of statements was compiled. RECOMMENDATIONS: Consensus was achieved that COVID-19 vaccines licensed only for intramuscular injection should be administered intramuscularly in hemophilia patients. Prophylactic factor replacement, given on the day of vaccination with a maximum interval between prophylaxis and vaccination of 24 hours (factor VIII and conventional factor IX concentrates) or 48 hours (half-life extended factor IX), should be provided in patients with moderate or severe hemophilia. Strong consensus was achieved that patients with mild hemophilia and residual factor activity greater than 10% with mild bleeding phenotype or patients on emicizumab usually do not need factor replacement before vaccination. Swelling, erythema, and hyperthermia after vaccination are not always signs of bleeding but should prompt consultation of a hemophilia care center. In case of injection-site hematoma, patients should receive replacement therapy until symptoms disappear. CONCLUSIONS: Consensus was achieved on recommendations for intramuscular COVID-19 vaccination after replacement therapy for hemophilia patients depending on disease severity.

Characterization of acute hereditary angioedema attacks during pregnancy and breast-feeding and their treatment with C1 inhibitor concentrate.

OBJECTIVE: The objective of the study was to investigate the rates and characteristics of hereditary angioedema (HAE) attacks associated with pregnancy, delivery, and the postpartum period and their treatment with C1 esterase inhibitor (INH) concentrate. STUDY DESIGN: This was an observational study including 22 women with type I HAE, with data collected before, during, and after 35 pregnancies (37 children) based on patient diaries, interviews, and case report forms. RESULTS: In 83% of pregnancies, attack rates increased during pregnancy; highest mean rates occurred in the second and third trimesters. C1-INH concentrate effectively controlled attacks and was safe for mothers and children. Low-plasma C1-INH activity during pregnancy tended to be associated with an increased chance of giving birth to a child with HAE. CONCLUSION: Increased attack rates during pregnancy in women with HAE are well controlled with C1-INH concentrate, indicating the clear benefit of integrating the availability of C1-INH concentrate into the management plan for these women during pregnancy and delivery.

Impact of inherited thrombophilia on venous thromboembolism in children: a systematic review and meta-analysis of observational studies.

BACKGROUND: The aim of the present study was to estimate the impact of inherited thrombophilia (IT) on the risk of venous thromboembolism (VTE) onset and recurrence in children by a meta-analysis of published observational studies. METHODS AND RESULTS: A systematic search of electronic databases (Medline, EMBASE, OVID, Web of Science, The Cochrane Library) for studies published from 1970 to 2007 was conducted using key words in combination as both MeSH terms and text words. Citations were independently screened by 2 authors, and those meeting the inclusion criteria defined a priori were retained. Data on year of publication, study design, country of origin, number of patients/controls, ethnicity, VTE type, and frequency of recurrence were abstracted. Heterogeneity across studies was evaluated, and summary odds ratios and 95% CIs were calculated with both fixed-effects and random-effects models. Thirty-five of 50 studies met inclusion criteria. No significant heterogeneity was discerned across studies. Although >70% of patients had at least 1 clinical risk factor for VTE, a statistically significant association with VTE onset was demonstrated for each IT trait evaluated (and for combined IT traits), with summary odds ratios ranging from 2.63 (95% CI, 1.61 to 4.29) for the factor II variant to 9.44 (95% CI, 3.34 to 26.66) for antithrombin deficiency. Furthermore, a significant association with recurrent VTE was found for all IT traits except the factor V variant and elevated lipoprotein(a). CONCLUSIONS: The present meta-analysis indicates that detection of IT is clinically meaningful in children with, or at risk for, VTE and underscores the importance of pediatric thrombophilia screening programs.

C1-inhibitor concentrate for individual replacement therapy in patients with severe hereditary angioedema refractory to danazol prophylaxis.

BACKGROUND: Hereditary angioedema (HAE) caused by functional deficiency of C1-inhibitor (C1-INH) is a rare disease that manifests with recurrent spontaneous nonallergic edema of the subcutaneous tissues and mucous membranes. In cases of laryngeal edema that are not treated immediately, HAE is associated with high mortality rates. Attenuated androgens (e.g., danazol) are usually administered for prophylaxis, but associated side effects may limit their use. This study investigated the efficacy, safety, and quality of life (QoL) associated with a pasteurized plasma-derived C1-inhibitor (pC1-INH) concentrate for individual replacement therapy (IRT) in patients with severe HAE suffering from frequent attacks who were intolerant or not responding to danazol. STUDY DESIGN AND METHODS: Twenty-two patients with severe HAE and danazol incompatibility or insufficient efficacy of danazol were recruited. Intraindividual comparisons of efficacy, safety, and QoL with pC1-INH concentrate IRT versus danazol treatment were made using retrospective and prospective patient data. Pharmacokinetic data were collected for 15 of the 22 patients. RESULTS: In patients receiving pC1-INH regularly, the median number of attacks per year decreased significantly compared to danazol prophylaxis (p < 0.001), and the 24 laryngeal edema episodes per year ceased. Superior efficacy of pC1-INH was found for all QoL variables (e.g., general condition, social activities). No transmission of human immunodeficiency virus or hepatitis A, B, or C was observed. CONCLUSION: In patients with severe HAE who experience severe side effects and/or lack of efficacy of danazol prophylaxis, very early substitution with pC1-INH can completely abolish the incidence of potentially fatal laryngeal edema and can reduce the incidence of acute attacks.

Prevalence of Obesity in Young Patients with Severe Haemophilia and Its Potential Impact on Factor VIII Consumption in Germany.

Similar to the general population, overweight and obesity have increasingly become a medical and economic burden also in patients with haemophilia in industrialized nations. In this study in seven German haemophilia centres, we identified a prevalence of overweight and obesity of 25.2% among 254 young patients <30 years (median: 13 years; range: 0-30 years) with severe haemophilia A and without a history of inhibitors. The median FVIII dosage based on bodyweight was significantly higher in normal weight compared with overweight or obese patients (96.9 vs. 72.9 IU/kg/week, respectively; p < 0.0001). This suggests that an individualized dosing regime which might be based on FVIII pharmacokinetics, physical activity and pre-existing haemophilic arthropathy is applied rather than dosing by bodyweight only. The bleeding rates observed in obese (median: 1; range: 0-17) versus normal weight patients (median: 2; range: 0-28) did not differ significantly (p = 0.057). Lower bleeding rates might be due to reduced activity or expected higher FVIII plasma levels in overweight patients. Due to the increasing prevalence of overweight/obesity in patients with haemophilia an interdisciplinary approach for individualized haemophilia treatment and weight loss programmes might be helpful for optimal and economical treatment for this group of patients.

Risk factors for recurrent venous thromboembolism in the European collaborative paediatric database on cerebral venous thrombosis: a multicentre cohort study.

BACKGROUND: The relative importance of previous diagnosis and hereditary prothrombotic risk factors for cerebral venous thrombosis (CVT) in children in determining risk of a second cerebral or systemic venous thrombosis (VT), compared with other clinical, neuroimaging, and treatment variables, is unknown. METHODS: We followed up the survivors of 396 consecutively enrolled patients with CVT, aged newborn to 18 years (median 5.2 years) for a median of 36 months (maximum 85 months). In accordance with international treatment guidelines, 250 children (65%) received acute anticoagulation with unfractionated heparin or low-molecular weight heparin, followed by secondary anticoagulation prophylaxis with low-molecular weight heparin or warfarin in 165 (43%). RESULTS: Of 396 children enrolled, 12 died immediately and 22 (6%) had recurrent VT (13 cerebral; 3%) at a median of 6 months (range 0.1-85). Repeat venous imaging was available in 266 children. Recurrent VT only occurred in children whose first CVT was diagnosed after age 2 years; the underlying medical condition had no effect. In Cox regression analyses, non-administration of anticoagulant before relapse (hazard ratio [HR] 11.2 95% CI 3.4-37.0; p<0.0001), persistent occlusion on repeat venous imaging (4.1, 1.1-14.8; p=0.032), and heterozygosity for the G20210A mutation in factor II (4.3, 1.1-16.2; p=0.034) were independently associated with recurrent VT. Among patients who had recurrent VT, 70% (15) occurred within the 6 months after onset. CONCLUSION: Age at CVT onset, non-administration of anticoagulation, persistent venous occlusion, and presence of G20210A mutation in factor II predict recurrent VT in children. Secondary prophylactic anticoagulation should be given on a patient-to-patient basis in children with newly identified CVT and at high risk of recurrent VT. Factors that affect recanalisation need further research.

Cerebral venous thrombosis in children: a multifactorial origin.

BACKGROUND: The present study was performed to assess the association of prothrombotic risk factors and underlying conditions (infections, vascular trauma, immobilization, malignancies, autoimmune diseases, renal diseases, metabolic disorders, obesity, birth asphyxia, cardiac malformations, and use of prothrombotic drugs) with cerebral venous thrombosis (CVT) in children. METHODS AND RESULTS: From 1995 to 2002, 149 pediatric patients aged newborn to <18 years (median 6 years) with CVT were consecutively enrolled. In patients and in 149 age- and gender-matched children with similar underlying clinical conditions but without CVT, the factor V G1691A mutation, the factor II G20210A variant, lipoprotein(a) [Lp(a)], protein C, protein S, antithrombin, and antiphospholipid antibodies, as well as associated clinical conditions, were investigated. Eighty-four (56.4%) of the patients had at least 1 prothrombotic risk factor compared with 31 control children (20.8%; P<0.0001). In addition, 105 (70.5%) of 149 patients with CVT presented with an underlying predisposing condition. On univariate analysis, factor V, protein C, protein S, and elevated Lp(a) were found to be significantly associated with CVT. However, in multivariate analysis, only the combination of a prothrombotic risk factor with an underlying condition (OR 3.9, 95% CI 1.8 to 8.6), increased Lp(a) (OR 4.1, 95% CI 2.0 to 8.7), and protein C deficiency (OR 11.1, 95% CI 1.2 to 104.4) had independent associations with CVT in the children investigated. CONCLUSIONS: CVT in children is a multifactorial disease that, in the majority of cases, results from a combination of prothrombotic risk factors and/or underlying clinical condition.

Role of protein S deficiency in children with venous thromboembolism. An observational international cohort study.

Venous thromboembolism [TE] is a multifactorial disease, and protein S deficiency [PSD] constitutes a major risk factor. In the present study the prevalence of PSD and the clinical presentation at TE onset in a cohort of children is reported. In 367 unselected paediatric patients with TE (age 0.1-18 years) recruited between July 1996 and December 2013, a comprehensive thrombophilia screening was performed along with recording of anamnestic data. Thirty of 367 paediatric patients (8.2 %) derived from 27 families had PSD. Mean age at first TE onset was 14.5 years (range 0.1 to 18). Thrombotic locations were cerebral veins (n=8), calf vein TE (n=3) deep veins (DVT) of the leg (n=12), DVT & pulmonary embolism (n=5) and intra-cardiac veins (n=1) or purpura fulminans (n=1). PSD co-occurred with the factor 5 mutation at rs6025 or the homozygous factor 2 susceptibility variant at rs1799963 in one case each. The Heerlen polymorphism detected in five children presented with milder PSD. In 18 patients (60 %) a concomitant risk factor for TE was identified. A second TE event within primarily healthy siblings occurred in three of 27 PSD families (11.0 %). In this cohort of children with symptomatic TE, the prevalence of PSD adjusted for family status was 7.4 %. 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.

Recurrent thromboembolism in infants and children suffering from symptomatic neonatal arterial stroke: a prospective follow-up study.

BACKGROUND AND PURPOSE: The present study was performed to evaluate the rate of recurrent symptomatic thromboembolism with respect to prothrombotic risk factors and underlying clinical conditions. METHODS: In a series of 215 consecutively enrolled neonates with arterial ischemic stroke (AIS), the factor V G1691A mutation, factor II G20210A variant, methylenetetrahydrofolate reductase (MTHFR) T677T genotype, lipoprotein (Lp) (a), antithrombin, protein C, protein S, and anticardiolipin antibodies (ACA) were investigated. Patient median follow-up was 3.5 years (range, 1 to 8 years). RESULTS: During follow-up, 7 infants and children (3.3%) showed recurrent symptomatic thromboembolism (AIS, n=4; venous sinus thrombosis, n=2; deep vein thrombosis of the leg, n=1). The factor V mutation, factor II variant, elevated Lp(a) >30 mg/dL, protein C deficiency, and protein S or antithrombin deficiency were associated with first stroke onset. In 5 of 7 cases (71.4%), prothrombotic risk factors [MTHFR T677T, elevated Lp(a), hyperhomocysteinemia, protein C deficiency] were involved at the time of recurrence. Furthermore, a second thromboembolic event was triggered additionally by underlying diseases (71%), eg, cardiac malformation and immobilization, diarrhea, mastoiditis, and moyamoya syndrome. CONCLUSIONS: Data shown here give evidence that symptomatic recurrent thromboembolism is not common in children with neonatal AIS. The risk of a second event, however, is increased when underlying diseases occur and prothrombotic risk factors are involved.

Maternal thrombophilia and neonatal thrombosis.

In neonates and infants, numerous clinical and environmental conditions lead to elevated thrombin generation and subsequent thrombus formation. Genetic prothrombotic defects (protein C, protein S and antithrombin deficiency, mutations of coagulation factor V and factor II, elevated lipoprotein (a)) have been established as risk factors of thromboembolic events in neonates and infants. The interpretation of the laboratory evaluation relies on age-dependent normal reference values. Because appropriate clinical trials are missing in these age groups, treatment recommendations are adapted from small-scale studies in neonates and infants and from guidelines relating to adult patient protocols. Secondary long-term anticoagulation should be administered on an individual basis.

Increased fasting total homocysteine plasma levels as a risk factor for thromboembolism in children.

Elevated total homocysteine (tHcy) concentrations are an independent risk factor for thromboembolic events in adults. In children with moderate hyperhomocysteinemia data are sparse. Therefore, between 1995 and 2002 we consecutively recruited 163 white pediatric patients with a first symptomatic thromboembolic event and 255 healthy controls (mean age: 6.4 years in patients vs. 6.6 years in controls, range: 3 months to 18 years) and measured fasting tHcy levels. Median tHcy levels in patients were significantly higher (6.6 micromol/l, range 2.9-20.4 micromol/l) than in controls (5.7 micromol/l, 2.0-14.0 micromol/l, p<0.0001). 48 of the 163 patients with thromboembolism (29.5%) versus 26 of the 255 controls (10.2%) had tHcy levels above the age-specific normal 90th percentile (OR 2.9, 95%CI: 1.7-4.8). The odds ratio for children in the highest quintile compared to children with levels in the lowest quintile was 4.3 (1.6-8.1; highest quintile: median tHcy level 9.6 micromol, range 8.0-20.4), showing a significantly increased risk for thromboembolic disease with even mild hyperhomocysteinemia. We conclude that hyperhomocysteinemia above the age-specific cut-off values is a risk factor for thromboembolic events in children. Therefore, screening for elevated fasting tHcy levels of patients with thromboembolism is recommended to stratify the risk of thromboembolism.