Anjali Sharathkumar

Linkage analysis identifies a locus for plasma von Willebrand factor undetected by genome-wide association

The plasma glycoprotein von Willebrand factor (VWF) exhibits fivefold antigen level variation across the normal human population determined by both genetic and environmental factors. Low levels of VWF are associated with bleeding and elevated levels with increased risk for thrombosis, myocardial infarction, and stroke. To identify additional genetic determinants of VWF antigen levels and to minimize the impact of age and illness-related environmental factors, we performed genome-wide association analysis in two young and healthy cohorts (n = 1,152 and n = 2,310) and identified signals at ABO (P < 7.9E-139) and VWF (P < 5.5E-16), consistent with previous reports. Additionally, linkage analysis based on sibling structure within the cohorts, identified significant signals at chromosome 2q12–2p13 (LOD score 5.3) and at the ABO locus on chromosome 9q34 (LOD score 2.9) that explained 19.2% and 24.5% of the variance in VWF levels, respectively. Given its strong effect, the linkage region on chromosome 2 could harbor a potentially important determinant of bleeding and thrombosis risk. The absence of a chromosome 2 association signal in this or previous association studies suggests a causative gene harboring many genetic variants that are individually rare, but in aggregate common. These results raise the possibility that similar loci could explain a significant portion of the “missing heritability” for other complex genetic traits.

Post-thrombotic syndrome in children: a single center experience.

Background Development of post-thrombotic syndrome (PTS) is increasingly being recognized as a complication of deep venous thrombosis (DVT) in children. Objective To determine the prevalence, clinical characteristics, and predictors of moderate to severe PTS in children. Methods A retrospective chart review was performed on those children who were followed in the coagulation clinic for objectively confirmed DVTs from December 2004 to December 2006. The scoring system used by Kuhle et al was used to grade the severity of PTS as: mild, moderate, and severe. Results PTS developed in 20% (11/55; 95% confidence interval 9.4-30.1) of children, in which 8/11 were moderate and 3/11 were severe. Median interval between diagnosis of PTS and DVT was 90 days (range, 46 d to 3 y). The majority (72.7%) of patients in the non-PTS group received treatment intervention within 48 hours of diagnosis of DVT. Delay in treatment initiation (>48 h) and recurrence of DVT were associated with the development of PTS (P<0.05). Variables including occlusive thrombus, location and number of vessels involved with DVT, age at diagnosis, underlying thrombophilia, intensity of anticoagulation, and body mass index were not associated with the development of PTS. Other debilitating consequences of DVT requiring intervention included portal hypertension (n=2), chylothorax (n=1), and reflux sympathetic dystrophy (n=1). The small sample size and limited follow up restricted the statistical analysis. Conclusions PTS is a significant problem in children with symptomatic DVTs. Early treatment intervention within the first 48 hours of diagnosis of DVT and prevention of thrombosis recurrence may prevent development of PTS. Although PTS refers to consequences of intravenous hypertension owing to extremity DVTs, sequlae of nonextremity DVTs require special consideration in pediatric PTS classification.

Clinical course of postthrombotic syndrome in children with history of venous thromboembolism.

Postthrombotic syndrome (PTS) is a chronic morbidity of venous thromboembolism (VTE) in children. Information about the evolution of PTS is lacking in children. Present study was aimed to evaluate the time-course of extremity PTS in children who were serially followed in a hematology clinic. This retrospective cohort study included 69 consecutive children with documented VTEs that presented with symptoms of extremity VTE: 67 extremity VTEs with or without extension to vena cava, 2 inferior vena cava VTEs. Severity of PTS was assessed using modified Villalta scale. Median age of the cohort was 12.6 years (interquartile range 1.6–15 years) while median follow-up was 28.7 months (interquartile range 13.3–33.4 months. PTS prevalence was 46.8% [95% confidence interval (CI) 37.9–57.7%]. Lower extremity VTE was associated with development of PTS compared to upper extremity VTE regardless of catheter use (P = 0.002). The time-course of PTS fluctuated in 11 of 33 children (33%; 95% CI 20–47%) at a median interval of 12 months from diagnosis of VTE (range 4–14 months): three progressed from mild/moderate to severe, one improved from moderate to mild, seven fluctuated between mild and moderate. Recurrence and incomplete resolution of VTE were associated with variability in PTS severity (P < 0.05). In summary, this study suggested that almost 50% of study cohort developed PTS, and the time-course of PTS was not static in one third of children. Future research should focus on identifying the predictors contributing to the worsening of PTS and developing risk-stratified treatment interventions so as to improve the outcome of children with VTE.

Successful eradication of inhibitor in a patient with severe haemophilia B and anaphylaxis to factor IX concentrates: is there a role for Rituximab and desensitization therapy?

loosely packed platelet thrombi with an increased predisposition towards embolization [8,9]. On this basis, she may be a candidate for aspirin. Taken together, these studies suggest that our patient had an increased tendency to form thrombi, and an increased lysis of clots that may have predisposed her to embolization. Our patient’s bleeding phenotype did not offset the increased risk for thrombosis incurred by indwelling central lines and exposure to oestrogen-containing oral hormonal contraception. Catheter-associated DVTs have been reported in afibrinogenemia patients on hFC [10]. Furthermore, she developed increased fibrinogen clearance during her acute PE. This observation has been reported previously in massive haemorrhage, major surgery and advanced pregnancy [4]. In summary, congenital afibrinogenemia is rare bleeding disorder. However, this disorder should also be considered prothrombotic, especially in high-risk settings. We have illustrated that afibrinogenemia with a bleeding phenotype is not protective from catheterassociated thrombosis or PE. Anticoagulation in these patients is challenging and requires careful monitoring, preferentially with anti-Xa levels, and increased doses of hFC may be required in the acute setting to prevent further bleeding in the setting of a consumptive coagulopathy.

Clinical advances in hemophilia management

Hemophilia is an excellent example in medicine where clinical translation of basic science discoveries has transformed the gloomy outlook of the disease. This review provides an overview of clinical advances in hemophilia management with a specific focus on the molecular heterogeneity of the disease and progress in management of patients with inhibitors. Novel therapeutics and the emerging ethical issues in the field of hemophilia are also discussed. Pediatr Blood Cancer 2011; 57: 910–920.

Current practice perspectives on the management of thrombosis in children with renal insufficiency: the results of a survey of pediatric hematologists in North America.

No guidelines exist for the management of venous thromboembolic events (VTE) in children with renal insufficiency (RI).

Autoimmune haemophilia in a teenager

Autoimmune haemophilia A (AHA) is a rare but potentially life-threatening disorder characterized by the sudden onset of bleeding in patients without a personal or family history of bleeding disorder. It is extremely uncommon in children. In this article, we describe the management of an adolescent girl with AHA who presented with acute hypovolaemic shock due to intraabdominal bleeding. The Northwestern University Institutional Review Board (IRB) determined that this report was exempt from IRB review. [Correction added on 8 October 2013 after first online publication: the statement on IRB approval has been corrected.] A previously healthy 13-year-old girl presented to an outside medical facility with intermittent abdominal pain for 2 weeks. She noticed a bruise on her left thigh, enlarging in size over a few days and tracking towards her calf. Her menstrual cycles began 1 day prior to presentation. She had no past history of unusual bleeding. On physical examination, there was a large bruise over her left medial thigh. Laboratory studies revealed a normocytic anaemia with haemoglobin of 8.0 g dL . A right adnexal mass measuring 6.5 9 5 9 5 cm was noted on abdominal ultrasound. She was referred to our centre for further evaluation for an oncological process. The activated partial thromboplastin time (APTT) was 73.3 s and the prothrombin time (PT) was 10 s. A urine pregnancy test was negative. A CT scan of the abdomen showed a 7.4 9 6.7 cm lobulated heterogeneous mass originating from the right ovary with retroperitoneal and pelvic fluid collections (Fig. 1a). In addition, there was an intramuscular mass measuring 10.3 9 2.9 cm within the right obturator internus muscle consistent with a haematoma (Fig. 1b). Due to the concern for bleeding from the right ovarian mass, an emergent exploratory laparotomy was planned to identify and control the site of intra-abdominal bleeding and to biopsy the ovarian mass. Just prior to the patient’s transfer to the operating room, the patient became hypotensive with a fall in haemoglobin to 6.5 g dL . Despite multiple fluid boluses, transfusion of three units of packed red blood cells, fresh frozen plasma and dopamine infusion, the blood pressure and haemoglobin remained depressed. The haematology service was consulted who suspected the diagnosis of AHA, and recommended treatment with a factor VIII (FVIII) bypassing agent. Recombinant human FVIIa (rFVIIa, NovoSeven ; NovoNordisk, Princeton, NJ, USA) 270 mcg kg , was given and bleeding stopped after one dose. She was continued on rFVIIa at 90 mcg kg 1 per dose IV every 4 h for 48 h. Coagulation assays revealed that the APTT did not correct with pooled plasma (1:1 mixture) and showed persistent prolongation after incubation (APTT after immediate mix 47 and 53 s after 1 h incubation at 37°C). The FVIII activity level was 0.08 U mL 1 and the FVIII inhibitor titre was 35 BU [1]. To suppress the inhibitor, she was commenced on prednisone, 1 mg kg 1 per day. After 48 h of rFVIIa therapy, factor eight inhibitor bypassing agent (FEIBA) was initiated at 85 IU of FIX activity per kg once daily. After 3 days, FEIBA doses were tapered to 50 IU kg 1 twice weekly, and she was discharged home. Within 2 weeks of discharge, she developed papular, pruritic skin lesions in close proximity to the IV infusion site, which coincided with FEIBA infusions. Due to a suspected allergic reaction to FEIBA, her treatment plan was changed to rFVIIa as needed. The prednisone was continued for 2 weeks followed by a gradual wean over the next 2 weeks. Upon initiation of steroids, she showed a reduction in inhibitor titres and increase in FVIII activity, 19 BU and 0.17 U mL , respectively, but shortly after the steroid taper, she was re-admitted with a right biceps bleed. At this time the inhibitor titres were elevated (61 BU) and FVIII levels were decreased to 0.05 U mL . Due to the relapse while on steroids, therapy with the anti-CD20 monoclonal antibody, Rituximab , at 375 mg m , was given weekly for 3 weeks. After the second dose of Rituximab , the FVIII inhibitor was undetectable and FVIII activity increased to within the normal range. The time course of the inhibitor titres and FVIII activities are shown in the Supplementary Appendix S1. Serial abdominal ultrasound examinations showed progressive decrease in the size of the ovarian mass, and a CT-scan at 6 months showed near complete resolution of the muscle haematoma without any calcification. To further evaluate her haemostasis, serial thrombin generation assays (TGAs) were performed (Technoclone GmbH, Vienna, Austria). The Table 1 shows the relationship between FVIII activity and the Correspondence: Surabhi Batra, MD, Pediatric Hematology/ Oncology and Stem-Cell Transplantation, Ann & Robert H. Lurie Children’s Hospital of Chicago, 224 East Chicago Avenue, Chicago, IL 60611, USA Tel.: +312 227 4000; fax: +312 227 4090; e-mail: sbara@luriechildrens.org

Bleeding disorders and Noonan syndrome.

To the Editor: We read with great interest a review article written by Briggs and Dickerman [1] published in February 2012 issue of Pediatric Blood & Cancer. In this review, the authors have summarized the clinical spectrum of bleeding disorders in patients with Noonan syndrome (NS). The authors also provide recommendations about performing screening tests for the evaluation of bleeding disorders, various management options for bleeding diathesis. We have concerns about these recommendations. Various algorithms are available to evaluate patients with suspected bleeding disorders. These algorithms are helpful to characterize disorders of primary, secondary hemostasis regardless of underlying disease pathology [2]. The authors recommend performing PTT/aPTT, bleeding time (BT), platelet count, factor XI levels as a first tier testing. I think, authors want to suggest PT, PTT instead of PTT/aPTT as PTT, aPTT provides the same information about the coagulation pathway. This screening test provides insight about the deficiencies of coagulation proteins involved in intrinsic, common pathway. With regard to BT, it is important to realize that in many institutions BT is replaced by the platelet function analyzer (PFA)-100 test. Normal values of BT, PFA-100 may not rule out primary hemostasis disorders and specifically platelet function abnormalities or von Willebrand disease (VWD). With regard to treatment of bleeding complications of unknown etiology in a patient with NS, the authors suggested using cryoprecipitate for the treatment of possible VWD. We believe this is incorrect, as cryoprecipitate does not contain von Willebrand factor (VWF). The primary clotting proteins available in cryprecipitate are fibrinogen, factor VIII, factor XIII, and fibrinectin. The use of cryoprecipitate will be appropriate if patient with NS experience disseminated intravascular coagulation or there is documented hypofibrinogenemia. In practice, cryoprecipitate and fresh frozen plasma are no longer recommended for the treatment of VWD due to the high volume and risk of viral transmission. It is important to underscore that both intermediate purity (e.g., Humate-P by CSL Behring) and high-purity (Wilate by Octapharma, USA) plasma derived VWF concentrates are available for the treatment for VWD [3]. Recombinant VWF products are in clinical trials. Considering the pace with which medicine is progressing, it is difficult to stay abreast with advances in different subspecialties of hematology and oncology. Therefore, it may be prudent to consult a hematologist while managing a patient with NS.