First prospective report on immune tolerance in poor risk haemophilia A inhibitor patients with a single factor VIII/von Willebrand factor concentrate in an observational immune tolerance induction study.

INTRODUCTION/BACKGROUND: Development of neutralizing inhibitors against factor VIII (FVIII) is a major complication of haemophilia A treatment. AIM: The ongoing, international, open-label, uncontrolled, observational immune tolerance induction (ObsITI) study evaluates ITI, the standard of care in patients with inhibitors. PATIENTS/METHODS: Forty-eight prospective patients in this interim analysis received a single plasma-derived, von Willebrand factor-stabilized, FVIII concentrate (pdFVIII/VWF) for ITI. According to recommended Bonn protocol, 'low responders' at ITI start (<5 BU) received 50-100 IU FVIII kg(-1) daily, or every other day; 'high responders' (≥5 BU) received 100 IU FVIII kg(-1) every 12 h. RESULTS: Forty of 48 patients (83.3%), had at least one risk factor for poor ITI-prognosis at ITI start (i.e. age ≥7 years, >2 years since inhibitor diagnosis, inhibitor titre ≥10 BU at the start of ITI, or prior ITI failure). Nonetheless, 34 patients (70.8%) achieved complete success, 3 (6.3%) partial success, 1 (2.1%) partial response; ITI failed in 10 patients (20.8%), all with poor prognosis factors. All six low responders achieved complete success. ITI outcome was significantly associated with inhibitor titre level at ITI start (P = 0.0068), number of poor prognosis factors for ITI success (P = 0.0187), monthly bleeding rate during ITI (P = 0.0005) and peak inhibitor titre during ITI (P = 0.0007). Twenty-two of 35 high responder patients (62.9%) with ≥1 poor prognosis factor achieved complete success. CONCLUSION: Treatment with a single pdFVIII/VWF concentrate, mainly according to the Bonn protocol, resulted in a high ITI success rate in haemophilia A patients with inhibitors and poor prognosis for ITI success.

Prophylaxis with FEIBA in paediatric patients with haemophilia A and inhibitors.

The benefits shown with factor VIII (FVIII) prophylaxis relating to joint health and quality of life (QoL) provide the rationale for FEIBA prophylaxis in haemophilia A patients with persistent FVIII inhibitors. FEIBA has previously shown efficacy in preventing bleeds in inhibitor patients who failed to respond to, or were ineligible for immune tolerance induction (ITI). The study examined the outcome of paediatric patients undergoing long-term FEIBA prophylaxis. A retrospective chart review included severe haemophilia A patients with persistent inhibitors aged ≤13 years at the start of FEIBA prophylaxis. Baseline characteristics captured dose, frequency of prophylaxis, history of inhibitor development, including baseline titre, historical peak titre and history of ITI. Outcome measurements included annual bleed rate before and during FEIBA prophylaxis, joint status and school days missed. Sixteen cases of FEIBA prophylaxis from two centres are presented. The mean age of subjects at prophylaxis initiation was 7.5 ± 3.6 years and median baseline inhibitor titre was 23 (range 3.1-170) BU. Prior to prophylaxis initiation, median annual joint bleeds among all patients was 4 (0-48), which dropped significantly after the first year of prophylaxis, to a median annual joint bleed rate of 1 (0-7; P = 0.0179). Subsequent years (median = 9) of prophylaxis therapy demonstrated similarly low annual joint bleed rates. There were no life-threatening bleeds, no viral seroconversions or thrombotic events during FEIBA prophylaxis treatment. FEIBA prophylaxis was effective for preventing joint bleeds and subsequent joint damage, delaying arthropathy and improving outcomes in children with haemophilia A and inhibitors to FVIII, who failed or were ineligible for ITI.

[Therapy of inherited diseases of platelet function. Interdisciplinary S2K guideline of the Permanent Paediatric Committee of the Society of Thrombosis and Haemostasis Research (GTH e. V.)]. / Therapie hereditärer Thrombozytopathien. Interdisziplinäre S2K-Leitlinie der Ständigen Kommission Pädiatrie der Gesellschaft für Thrombose- und Hämostaseforschung e. V.

Inherited disorders of platelet function are a heterogeneous group. For optimal prevention and management of bleeding, classification and diagnosis of the underlying defect are highly recommended. An interdisciplinary guideline for a diagnostic approach has been published (AWMF # 086-003 S2K; Hämostaseologie 2014; 34: 201-212). Underlying platelet disorder, platelet count, age and clinical situation modify treatment. Exclusive transfusion of platelet concentrates may be inappropriate as potentially adverse effects can outweigh its benefit. A stepwise and individually adjusted approach for restitution and maintenance of haemostasis is recommended. Administration of antifibrinolytics is generally endorsed, but is of particular use in Quebec disease. Restricted to older children, desmopressin is favourable in storage pool disease and unclassified platelet disorders. Although licensed only for patients with Glanzmann thrombasthenia and alloantibodies, in clinical practice rFVIIa is widely used in inherited platelet disorders with severe bleeding tendency. This guideline aims at presenting the best available advice for the management of patients with inherited platelet function disorders.

Characterization of prodromal symptoms in a large population of patients with hereditary angio-oedema.

BACKGROUND: Hereditary angio-oedema (HAE) due to C1-inhibitor (C1-INH) deficiency is a rare autosomal dominant disease. It predisposes affected patients to attacks of disfiguring, painful angio-oedema, which, in cases of involvement of the upper airways, can be life-threatening. Frequently, prodromal symptoms occur hours to days before an attack, but their predictive value is uncertain. AIM: To characterize the spectrum of prodromal symptoms in patients with HAE in Germany. METHODS: A questionnaire asking about the frequency, type and time of occurrence of prodromal symptoms, and the interval until the onset of an attack of HAE was sent to 808 German patients with HAE. Answers from 365 participating patients were analysed. RESULTS: The survey showed that 79% of patients with HAE had experienced ≥ 1 prodromal symptom before an attack of angio-oedema. The most commonly reported prodromal symptoms (67% of which occurred within 6 h before an attack) were fatigue, malaise and short temper. Significantly more women than men reported having prodromes (83% vs. 73%, P < 0.05). Over 90% of the patients with prodromes reported that they were able to predict the onset of an attack with a certainty of ≥ 50%. In addition, there was a significant correlation between the occurrence of skin rashes and delay in the diagnosis of HAE. CONCLUSIONS: The results of this survey may aid the management of C1-HAE by recognizing that prodromal symptoms are of value in predicting the onset of an attack of angio-oedema and in diagnosing the condition.

A review of immune tolerance induction with Haemate P in haemophilia A.

Immune tolerance induction (ITI) has been shown to successfully eliminate factor VIII (FVIII) inhibitors in haemophilia patients with inhibitors. We performed a literature search to identify reports from January 1980 to October 2012 on the use of the plasma-derived, von Willebrand factor (VWF)-containing FVIII concentrate Haemate P/Humate-P in the setting of ITI. Six reports were identified that specifically evaluated the use of Haemate P/Humate-P including 32 children and 9 adults. Dosing regimens ranged from 20 IU kg(-1) every 2-3 days in patients with low-responding (LR; n = 5) inhibitors to 300 IU kg(-1) day(-1) in patients with high-responding (HR; n = 36) inhibitors. Complete success was achieved in all five LR patients, in all three HR patients with good prognostic factors (age ≤7 years, pre-ITI inhibitor titre <10 BU, historical inhibitor titre <200 BU, time between inhibitor detection and ITI start <2 years), and in 24 of 33 (73%) HR patients with poor prognostic factors. The time to complete success was 0.5-4 months in good-prognosis patients and 0.5-42 months in poor-prognosis patients. Few adverse events were observed during ITI, and no cases of inhibitor relapse were reported with follow-up periods of up to 12 years. On the basis of this retrospective review of a diverse range of studies and case reports, we conclude that Haemate P/Humate-P for ITI in patients with inhibitors is effective and produces high rates of ITI success.

Risk of angioedema following invasive or surgical procedures in HAE type I and II--the natural history.

BACKGROUND: Hereditary angioedema (HAE), caused by deficiency in C1-inhibitor (C1-INH), leads to unpredictable edema of subcutaneous tissues with potentially fatal complications. As surgery can be a trigger for edema episodes, current guidelines recommend preoperative prophylaxis with C1-INH or attenuated androgens in patients with HAE undergoing surgery. However, the risk of an HAE attack in patients without prophylaxis has not been quantified. OBJECTIVES: This analysis examined rates of perioperative edema in patients with HAE not receiving prophylaxis. METHODS: This was a retrospective analysis of records of randomly selected patients with HAE type I or II treated at the Frankfurt Comprehensive Care Centre. These were examined for information about surgical procedures and the presence of perioperative angioedema. RESULTS: A total of 331 patients were included; 247 underwent 700 invasive procedures. Of these procedures, 335 were conducted in 144 patients who had not received prophylaxis at the time of surgery. Categories representing significant numbers of procedures were abdominal (n = 113), ENT (n = 71), and gynecological (n = 58) procedures. The rate of documented angioedema without prophylaxis across all procedures was 5.7%; in 24.8% of procedures, the presence of perioperative angioedema could not be excluded, leading to a maximum potential risk of 30.5%. Predictors of perioperative angioedema could not be identified. CONCLUSION: The risk of perioperative angioedema in patients with HAE type I or II without prophylaxis undergoing surgical procedures ranged from 5.7% to 30.5% (CI 3.5-35.7%). The unpredictability of HAE episodes supports current international treatment recommendations to consider short-term prophylaxis for all HAE patients undergoing surgery.

The immune tolerance induction (ITI) dose debate: does the International ITI Study provide a clearer picture?

Among the proposed predictors for immune tolerance induction (ITI) outcome, the therapeutic regimen - specifically the dose and frequency of administered factor VIII (FVIII) as well as FVIII product type - is intensely debated. Are there any advantages for low-dose regimens (50 IU FVIII kg(-1) three times a week) over high-dose regimens (200 IU FVIII kg day(-1)) or vice versa? Are von Willebrand factor (VWF)-containing plasma-derived concentrates superior to recombinant FVIII concentrates for tolerance induction? A review of the available literature indicates that patients with good prognostic factors can achieve success with either low-dose or high-dose ITI regimens. Retrospective data suggest that patient characteristics such as maximum historical inhibitor titres and pre-ITI inhibitor titres are better predictors of treatment success than dose. Results of the prospective International ITI Study have recently become available. In inhibitor patients with good prognosis, success rates were similar between low-dose (50 IU FVIII kg(-1) three times a week) and high-dose (200 IU FVIII kg(-1) daily) regimens. However, patients receiving low-dose ITI took longer to achieve various ITI milestones and had a significantly higher bleed rate per month compared with the high-dose group (0.62 vs. 0.28; P = 0.00024), findings with important clinical implications. Inhibitor patients with poor prognostic features should be treated with a high-dose protocol. This conclusion is supported by a meta-analysis of the International Immune Tolerance Registry and North American Immune Tolerance Registry and by data from Germany showing good success rates with the high-dose, high-frequency Bonn protocol in poor prognosis patients. Type of concentrate also appears to have an influence on ITI success rates in this patient subgroup, with evidence suggesting an advantage for VWF-containing plasma-derived FVIII concentrates over recombinant or VWF-free concentrates. The ongoing prospective studies REScue Immunotolerance STudy and Observational Immune Tolerance Induction are evaluating ITI outcome with respect to product type and are expected to answer this important clinical question as well as provide greater insight into patient- and therapy-related variables in inhibitor patients with poor prognostic features.

Hereditary angioedema (HAE) in children and adolescents--a consensus on therapeutic strategies.

Hereditary angioedema due to C1 inhibitor (C1 esterase inhibitor) deficiency (types I and II HAE-C1-INH) is a rare disease that usually presents during childhood or adolescence with intermittent episodes of potentially life-threatening angioedema. Diagnosis as early as possible is important to avoid ineffective therapies and to properly treat swelling attacks. At a consensus meeting in June 2011, pediatricians and dermatologists from Germany, Austria, and Switzerland reviewed the currently available literature, including published international consensus recommendations for HAE therapy across all age groups. Published recommendations cannot be unconditionally adopted for pediatric patients in German-speaking countries given the current approval status of HAE drugs. This article provides an overview and discusses drugs available for HAE therapy, their approval status, and study results obtained in adult and pediatric patients. Recommendations for developing appropriate treatment strategies in the management of HAE in pediatric patients in German-speaking countries are provided.Conclusion Currently, plasma-derived C1 inhibitor concentrate is considered the best available option for the treatment of acute HAE-C1-INH attacks in pediatric patients in German-speaking countries, as well as for short-term and long-term prophylaxis.

A multi-centre study of efficacy and safety of Intratect®, a novel intravenous immunoglobulin preparation.

We studied the efficacy, safety and pharmacokinetic profiles of Intratect®, a recently developed polyvalent intravenous immunoglobulin (IVIG) preparation. Fifty-one patients (aged 6-48 years) with primary immunodeficiencies (PID) and established replacement therapy using a licensed IVIG were enrolled and treated for 12 months with Intratect®. Retrospective patient data served as prestudy controls. The primary efficacy variable was the annual rate of acute serious bacterial infection (ASBI) per patient. Secondary parameters were annual rate of acute relevant infection (ARI), days with antibiotic use, fever, absence from school/work and hospitalization. The average IVIG dose was 0·49 g/kg, with an average infusion rate of 2·4 ml/kg/h. The annual ASBI rate/patient was 0·02 and ARIs were detected 128 times during the 630 adverse events in 40 patients, specified mainly as bronchitis, sinusitis, respiratory tract infection, rhinitis and pharyngitis. The annual rate of respiratory ARIs/patient was 2·0 and the rates/patient for days with fever >38°C, school/work absence and hospitalization were 1·81, 3·99 and 0·36, respectively. A total of 630 adverse events (AEs) were observed in 50 of 51 (98·0%) of patients. In 46 of 51 patients the AEs were not related to infusion. Pharmacokinetic studies after the first infusion revealed a mean elimination half-life of 50·8 ± 30·3 days. During this study, 19 of 649 (2·9%) IgG trough levels were below 6 g/l, better than that of reference IVIGs during the 6 months before study start (10 of 201). These data suggest that Intratect® is a well tolerated, safe and effective IgG concentrate for the treatment of patients with PID.

Rate of inhibitor development in previously untreated hemophilia A patients treated with plasma-derived or recombinant factor VIII concentrates: a systematic review.

BACKGROUND: Different rates of inhibitor development after either plasma-derived (pdFVIII) or recombinant (rFVIII) FVIII have been suggested. However, conflicting results are reported in the literature. OBJECTIVES: To systematically review the incidence rates of inhibitor development in previously untreated patients (PUPs) with hemophilia A treated with either pdFVIII or rFVIII and to explore the influence of both study and patient characteristics. METHODS: Summary incidence rates (95% confidence interval) from all included studies for both pdFVIII and rFVIII results were recalculated and pooled. Sensitivity analysis was used to investigate the effect of study design, severity of disease and inhibitor characteristics. Meta-regression and analysis-of-variance were used to investigate the effect of covariates (testing frequency, follow-up duration and intensity of treatment). RESULTS: Two thousand and ninety-four patients (1965 treated with pdFVIII, 887 with rFVIII; median age, 9.6 months) from 24 studies were investigated and 420 patients were observed to develop inhibitors. Pooled incidence rate was 14.3% (10.4-19.4) for pdFVIII and 27.4% (23.6-31.5) for rFVIII; high responding inhibitor incidence rate was 9.3% (6.2-13.7) for pdFVIII and 17.4% (14.2-21.2) for rFVIII. In the multi-way anova study design, study period, testing frequency and median follow-up explained most of the variability, while the source of concentrate lost statistical significance. It was not possible to analyse the effect of intensity of treatment or trigger events such as surgery, and to completely exclude multiple reports of the same patient or changes of concentrate. CONCLUSIONS: These findings underscore the need for randomized controlled trials to address whether or not the risk of inhibitor in PUPs with hemophilia A differs between rFVIII and pdFVIII.

Early long-term FEIBA prophylaxis in haemophilia A patients with inhibitor after failing immune tolerance induction: A prospective clinical case series.

Persistent high-titre inhibitors after immune tolerance induction (ITI) increase the risks of haemorrhage and arthropathy, resulting in high morbidity and mortality. Long-term prophylaxis with bypassing agents may avert these risks. This study was performed to assess the effectiveness and safety of early prophylaxis with FEIBA in preventing bleeding and joint damage after failed ITI. Seven paediatric patients proceeded immediately after failed ITI to long-term FEIBA prophylaxis at 60-100 IU kg(-1) dosages and various dosing intervals depending upon bleeding tendency. Bleeding episodes and joint status were assessed. Thrombin generation assays (TGA) were also used to gauge treatment response. FEIBA prophylaxis was commenced at a median age of 6.0 years (range, 1.5-11.8 years) and continued for a median duration of 6.9 years (range, 0.8-17.1 years). The mean annual incidence of joint bleeding was 1.5 episodes per year with a 95% CI of 0.7-3.0 episodes per year. Muscle bleeding incidence was 0.9 episodes per year (CI, 0.6-1.2 episodes per year). No patient experienced major joint damage during prophylaxis. Median Pettersson and orthopaedic joint scores at the last follow-up evaluation were 4 (range, 0-12) and 2 (range, 0-4) respectively. Endogenous thrombin potential (ETP) measured by TGA exceeded 80% of normal after FEIBA infusion in the majority of the patients. Between regular prophylactic infusions, mean trough ETP equalled 2.6 fold of the inhibitor plasma control mean. FEIBA prophylaxis was well-tolerated without serious thrombotic or other complications. The only adverse event involved venous access. Therefore early long-term FEIBA prophylaxis is valuable in controlling bleeding and preserving joint integrity in young patients failing ITI.

Inhibitor treatment by rituximab in congenital haemophilia A - Two case reports.

UNLABELLED: The development of neutralizing alloantibodies (inhibitors) to factor VIII (FVIII) is one of the most serious complications in the treatment of haemophiliacs. Inhibitors occur in approximately 20 to 30% of previously untreated patients (PUPs), predominantly children, with severe haemophilia A within the first 50 exposure days (ED). Immune tolerance induction (ITI) leads to complete elimination of the inhibitor in up to 80% of the patients and offers the possibility to restore regular FVIII prophylaxis. However, patients with high titre inhibitors, in whom standard ITI fails, usually impose with high morbidity and mortality and therefore prompting physicians to alternate therapy regimens. Rituximab, an anti-CD 20 monoclonal antibody has been successfully used in children and adults for the management of B-cell mediated disorders. We report on the use of a new protocol including rituximab in two adolescents with severe haemophilia A and high titre inhibitors, severe bleeding tendency and high clotting factor consumption after failing standard ITI. Both patients received a concomitant treatment with FVIII according to the Bonn protocol, cyclosporine A and immunoglobulin. Treatment with rituximab resulted in a temporary B-cell depletion leading to the disappearance of the inhibitor. FVIII recovery and half-life turned towards normal ranges. In patient 1 the inhibitor reappeared 14 months after the last rituximab administration. In patient 2 complete immune tolerance could be achieved for 60 months. Bleeding frequency diminished significantly and clinical joint status improved in both patients. In patient 1 the treatment course was complicated by aspergillosis and hepatitis B infection. CONCLUSION: Rituximab may be favourable for patients with congenital haemophilia, high-titre inhibitors and a severe clinical course in whom standard ITI has failed. Prospective studies are required to determine safety, efficacy and predictors of success.

Factor VII deficiency: clinical manifestation of 717 subjects from Europe and Latin America with mutations in the factor 7 gene.

The congenital FVII deficiency (FVIID) is a rare haemorrhagic disorder with an autosomal recessive pattern of inheritance. Data on phenotype and the genotype from 717 subjects in Central Europe (six countries), Latin America (Costa Rica, Venezuela) and United States, enrolled in the Greifswald Registry of FVII Deficiency were analysed. We detected 131 different mutations in 73 homozygous, 145 compound heterozygous and 499 heterozygous subjects. Regional differences were observed in the mutation pattern and the clinical profile of the evaluated patients. Seventy-one per cent of homozygous and 50% of compound heterozygous subjects were symptomatic. The clinical manifestations of the homozygous subjects were characterized by intracranial haemorrhage (2%), gastrointestinal bleeding (17%), haemarthrosis (13%), epistaxis (58%), gum bleeding (38%), easy bruising (37%), haematoma (15%), haematuria (10%) and menorrhagia (19 of 26 females, 73%). The clinical variability and genotype-phenotype correlation was evaluated in the homozygous subjects. The pattern of bleeding symptoms among compound heterozygous patients was severe and similar to that of the homozygous patients. The large-scale analysis of 499 heterozygous subjects shows that 93 (19%) presented with spontaneous bleeding symptoms such as haemarthrosis (4%), epistaxis (54%), gum bleeding (14%), easy bruising (38%), haematoma (23%), haematuria (5%) and menorrhagia (19 of 45 females; 42%). The severe haemorrhages - intracranial and gastrointestinal - were not reported in heterozygous subjects. The clinical variability and the regional differences in the mutation pattern are discussed regarding care and treatment.

Mutational spectrum of the C1INH (SERPING1) gene in patients with hereditary angioedema.

Hereditary angioedema (HAE) is an autosomal dominant disease that manifests as intermittent acute swellings of the skin and mucosal surfaces, which, in the gastrointestinal tract and larynx, may even be fatal. HAE results from functional deficiency of the C1 inhibitor (C1INH) protein, which plays a key role in the classical pathway of complement activation. C1INH is the sole inhibitor of the activated proteases C1r and C1s, and is the major regulator of activated coagulation Factor XII and plasma kallikrein, which limits the generation of the vasoactive peptide bradykinin. In this paper, we report on the genetic analysis of 173 families (including 326 members) with a clinical diagnosis of HAE. Direct sequencing, Southern blotting and quantitative PCR by the MLPA method were used to screen for mutations in C1INH (SERPING1). In 142 families (82.1%), a causative C1INH gene mutation could be identified. A total of 80 novel point mutations of C1INH not published previously were detected in 96 pedigrees (including 172 members). Our results corroborate C1INH (SERPING1) deficiency as a disease of extreme allelic heterogeneity with almost each individual family carrying their own mutation. Routine molecular genetic analysis is an effective way of confirming the clinical diagnosis and identifying mutation carriers early on before any clinical manifestation becomes apparent. It is, therefore, a valuable tool in prevention and adequate treatment of acute and life-threatening oedema.

Haemate P/Humate-P for the treatment of von Willebrand disease: considerations for use and clinical experience.

von Willebrand disease (VWD) is a heterogeneous bleeding disorder with symptoms in affected patients ranging from mild effects to potentially devastating haemorrhagic events. Desmopressin (DDAVP) and von Willebrand factor/factor VIII (VWF/FVIII) concentrates are the principal treatments. Haemate P/Humate-P is an intermediate-purity VWF/FVIII concentrate with extensive clinical experience in VWD. This concentrate has been shown to correct haemostatic defects of VWD, with efficacy ratings of good/excellent in nearly all patients treated for bleeding or surgical events. Haemate P/Humate-P has a high content of the high molecular weight (HMW) VWF multimer fraction, which has been shown to be very effective in achieving haemostasis. The HMW VWF multimer pattern in Haemate P/Humate-P is more similar to that of normal human plasma (94% for Haemate P/Humate-P vs. 100% for normal human plasma) than that of other VWF/FVIII concentrates and correlates with functional VWF activities including ristocetin cofactor activity (VWF:RCo) and collagen-binding activity. The recommended dosing of Haemate P/Humate-P is based preferentially on VWF:RCo activity, which is approximately twice that of FVIII:C (2.4:1). Haemate P/Humate-P has been shown to be safe; no serious adverse events or cases of thrombosis have been observed in clinical trials and no documented cases of viral transmission in nearly three decades of clinical use. While DDAVP is effective in a large proportion of VWD patients, it may not provide adequate haemostasis in all situations. In such cases, Haemate P/Humate-P is an effective replacement concentrate for all types of VWD in both adult and paediatric patients.

Immune tolerance induction with mycophenolate-mofetil in two children with haemophilia B and inhibitor.

Immune tolerance induction (ITI) in haemophilia B patients with inhibitor should be carefully considered because of the relatively poor (25%) overall success rate and the high risk of complications. ITI in combination with an immunosuppressive treatment was started in two children with haemophilia B with factor IX (FIX) inhibitor. To avoid anaphylactic reactions and inhibitor boost, the FIX replacement therapy was stopped and patients received a treatment with recombinant activated factor VII (rFVIIa). After disappearance of FIX inhibitor, a combination of mycophenolate-mofetil (MMF), dexamethasone (DEXA) and intravenous immunoglobulin (IVIG) and a high dose FIX replacement therapy was started. Immune tolerance could be induced in patient 2, whereas eradication of FIX inhibitor was incomplete in patient 1. Both patients benefited from the immune suppressive treatment and FIX replacement therapy was tolerated without any allergic complications. Neither development of a nephrotic syndrome nor a severe bleeding episode was observed. Strategies to induce tolerance in haemophilia B patients with inhibitors need to be explored in a systematic way. Given the low frequency of disease and even lower incidence of inhibitors, prospective randomized studies may not be possible. International registry-based retrospective and prospective data collection could play the key role in the study of the outcome variables in ITI for haemophilia B.

A common 253-kb deletion involving VWF and TMEM16B in German and Italian patients with severe von Willebrand disease type 3.

BACKGROUND: Severe von Willebrand disease (VWD) type 3 is caused by large deletions, insertions, small truncating mutations, splice site mutations and missense mutations of the VWF gene, respectively. Large deletions have been regarded as being a rare cause of VWD type 3. Complete gene deletions have only been identified in Italian and German patients to date. However, their extent and breakpoints have not been determined yet. OBJECTIVES: To identify the breakpoints of complete VWF deletions in patients with VWD type 3. PATIENTS/METHODS: Five index patients with large deletions from two unrelated German and three Italian families were investigated by polymerase chain reaction (PCR) and primer walking. Haplotypes were composed of eight deletion flanking markers. RESULTS: After initial characterization of a homozygous 253,246 bp deletion (Delta253 k) in a German patient, with the centromeric breakpoint located between CD9 and VWF and the telomeric breakpoint in intron 3 of TMEM16B, respectively, we identified the same Delta253 k in an additional two homozygous and two compound-heterozygous patients, and in their heterozygous parents. All patients share the same deletion-associated marker haplotype. The genomic structure of the breakpoint regions favors DNA double-strand breaks followed by non-homologous end-joining repair as an underlying molecular mechanism rather than a homologous recombination event. CONCLUSIONS: Our results suggest a single genetic origin of Delta253 k. Homozygosity for Delta253 k in non-consanguineous families from two different countries may indicate a higher incidence of large deletions in VWD type 3 than previously thought. The availability of a Delta253k-specific assay allows simple and rapid detection of even heterozygous patients and carriers.