Therapeutic embolization and surgical excision of haemophilic pseudotumour

Haemophilic pseudotumour is a rare complication of haemophilia. Few cases of iliac haemophilic pseudotumour have been reported in the literature. These tumours can act as a focus for infection and cause cutaneous fistulas. When they present perforations and infections of endogenous origin their course is usually fatal. Suitable treatment has been investigated on numerous occasions, most of the literature agreeing that the only curative treatment is surgical resection. We present a case of haemophilic pseudotumour of the iliac and caecum with cutaneous fistulas, with a septic process of endogenous origin. It was treated with surgical resection after performing arterial embolization to reduce the vascularization of the pseudotumour, thereby reducing its size and the risk of bleeding complications during surgery.     

Pre-operative synovial hyperaemia in haemophilia patients undergoing total knee replacement and the effects of genicular artery embolization: A retrospective cohort study

Aim

Haemophilia is characterized by recurrent joint bleeding caused by a lack of clotting factor VIII or IX. Due to repeated joint bleeding, end-stage arthropathy occurs in relatively young patients. A total knee replacement (TKR) can be a solution. However, TKR may be complicated by perioperative and postoperative bleeds despite clotting factor therapy. The aim of this study was to evaluate the prevalence of pre-operative synovial hyperaemia and the effects of Genicular Artery Embolization on synovial hyperaemia and 3-month postoperative joint bleeding.

Methods

In this retrospective cohort study, all patients with haemophilia who underwent periarticular catheter angiography between 2009 and 2020 were evaluated after written informed consent. Synovial hyperaemia on angiography was scored by an interventional radiologist.

Results

Thirty-three angiography procedures in 24 patients were evaluated. Median age was 54.4 years (IQR 48.4–65.9). Preoperative synovial hyperaemia was observed in 21/33 joints (64%). Moderate and severe synovial hyperaemia was observed in 10/33 joints (30%). Synovial hyperaemia decreased in 13/15 (87%) joints after embolization. Three-month postoperative joint bleeding occurred in 5/32 joints: in 2/18 joints (11%) without synovial hyperaemia and in 3/14 joints (21%) with mild synovial hypertrophy. Non-embolized and embolized joints did not differ regarding 3-month postoperative bleeding (P = .425). No complications were observed after embolization.

Conclusion

One-third of patients with haemophilia requiring a TKR had moderate or severe synovial hyperaemia which can be reduced safely by Genicular Artery Embolization prior to TKR. Three-month postoperative bleeding appears to occur independently of the presence of residual mild synovial hyperaemia.     

Successful angiographic embolization of recurrent elbow and knee joint bleeds in seven patients with severe haemophilia

Summary.  In haemophilic joints with high-grade arthropathy, bleeds occur that do not respond to replacement therapy of the deficient coagulation factor. The reason may be pathologically reactive angiogenesis in chronic synovitis. Seven patients with severe haemophilia A or haemophilia B experienced recurrent massive bleeds of one elbow joint or knee joint in the absence of trauma. After initial application of factor VIII or IX (fVIII/fIX; 50 IU kg⁻¹ bodyweight), there was only slow and never complete relief of symptoms. Despite intensive secondary prophylaxis maintaining the plasma level of factor concentrate at minimum 50%, new massive bleeds at the same location occurred. Vascular bleeding was suspected. Angiography of the arteries was performed via the femoral artery. Vessels identified as potential bleeding sources were embolized with embolization fluid (ONYX) in eight joints (six elbow and two knee joints). Under low-dose prophylactic treatment (15 IU fVIII or fIX per kg bodyweight for three times per week), no recurrent severe bleed unresponsive to coagulation factor replacement occurred after a mean observation time of 16 months after embolization. The consumption of factor concentrate decreased to one-third of the amount consumed before embolization. In conclusion, angiographic embolization with a non-adhesive liquid embolic agent might be considered as a promising therapeutic and coagulation factor saving option in joint bleeds not responding to replacement of coagulation factor to normal levels.     

Successful combination therapy of a proximal haemophilic pseudotumour with surgery, radiation and embolization in a child with mild haemophilia A

We describe the management of a young boy with mild haemophilia A and a massive iliac pseudotumour with a multi modality approach involving factor replacement, radiation therapy, embolization and surgery. The patient was initially treated with recombinant factor VIII and radiation therapy. Because of inadequate response and worsening of bony erosion, the patient had a preoperative embolization followed by surgical excision. The surgical procedure was associated with minimal blood loss and the patient had a relatively smooth postoperative course with no physical morbidity. This case illustrates successful aggressive management of a large, proximally located pelvic pseudotumour, which resulted in an excellent outcome despite the need for a normally morbid operation.     

Haemophilia and thrombophilia: an unexpected association!

In patients with haemophilia, a close correlation is usually observed between the clinical expression of the disease and plasmatic factor VIII/factor IX clotting activity. However, some patients experience milder bleeding phenotypes than others, although they exhibit a similar biological profile. The high prevalence of some inherited thrombophilia risk factors offers the possibility of a co-inheritance in haemophilic patients which could influence the phenotypic expression of the disease. Rare thrombotic complications occurring in haemophiliacs could also be facilitated by the co-inheritance of modifier genes. The majority of thrombotic events occurring in haemophiliacs are in relation to clotting factor infusions or central venous catheters. Concerning surgical situations, in the absence of therapeutic recommendations, postoperative thromboprophylaxis is not systematically performed in haemophiliacs. However, substitutive treatment more or less completely corrects the coagulation defect and makes the venous thrombosis risk closer to the control population. It should be emphasized that haemophilia does not fully protect against venous thromboembolic disease. Patients with haemophilia very infrequently experience thrombotic events. Thus, the management of thrombotic complications occurring in haemophilic patients should be discussed in each case according to the precipitating risk factors, the clinical context and the thrombo-haemorrhagic balance of the patient with respect to a particular clinical situation.     

Dose and response in haemophilia--optimization of factor replacement therapy

The mainstay of the management of haemophilia is the replacement of clotting factors, using clotting factor concentrates (CFC) in a way that prevents bleeding and its complications. Beginning with small doses, as whole blood and plasma over 50 years ago, highly purified CFCs are now administered frequently in large doses to effectively treat this condition so that even people with severe haemophilia can lead near normal lives. However, with such regimens, compliance and expense have both become significant issues. The question therefore is whether the current models of clotting factor replacement are optimal. This article reviews the literature on the dose-response relationship in haemophilia, with particular reference to management of musculoskeletal bleeding and surgical haemostasis. Current practices are based on uncontrolled observational data. Less intensive protocols could achieve similar outcomes. Large multi-centre prospective studies are needed to provide comparative data on unresolved issues so that factor replacement therapy can be optimized, based on evidence.     

Current state of play regarding dental extractions in patients with haemophilia: Consensus or evidence‐based practice? A review of the literature

Due to the global prevalence of oral disease, tooth extraction is the most common surgical procedure required in general population thus likely to be similarly common in patients with haemophilia, especially those in older age and those living in countries with restricted resources. There are little or no consensus about optimal level and duration of factor replacement (FRP) therapy required to prevent bleeding complication following surgery and low levels of evidence to inform protocols and guidelines. The goal of this article was to review the literature regarding haematological treatment protocols and to assess their effectiveness in prevention of bleeding complications during and after tooth extractions in people with haemophilia. A total number of 29 articles were identified. Only two of the studies were randomized controlled trials, and meta‐analysis was not possible. Significant heterogeneity regarding haematological regimes, dental surgical procedures, disease severity and sample size of published studies which are unable to reliably inform the provision of safe dental surgery was noted. Based on the haematological regimens, all studies were classified into one of three groups: pre‐ and postoperative FRP or DDAVP, single preoperative FRP or DDAVP, and no FRP treatment. The overall reported bleeding rate in case of both pre‐ and postoperative FRP and single dose FRP preoperative is similar, 11.9% and 11.4%, respectively, indicating that minimizing the use of clotting factor concentrate is possible if proper local haemostatic measures are provided. Strictly designed prospective studies with higher number of patients are necessary to get firm conclusions about optimal FRP treatment required to prevent bleeding complications during and after oral surgery in patients with haemophilia.     

Von Willebrand disease within the collective of haemophilic patients as reason for unexpected bleeding episodes

In the treatment of haemophilia A and B, recombinant coagulation factors are increasingly replacing plasma-derived factor VIII and IX concentrates. Although provided with replacement therapy, individual patients may exhibit bleeding episodes, which are difficult to control. These bleeds may be caused by von Willebrand disease (VWD) as an additional underlying coagulation disorder. We report in the present study our experience that in the collective of haemophilic patients, VWD must be anticipated at least with the same order of magnitude as it appears in a normal healthy population. Among the patients at our treatment centre, two patients (1.5%) were identified as suffering from VWD in addition to haemophilia A. In the collective of haemophilia B patients at our centre, three patients (10%) with VWD were found. Two of these patients exhibited unexpected severe bleeding episodes, which could only satisfactorily be controlled by the administration of Haemate-P or DDAVP supplementary to the recombinant coagulation factor concentrate.     

Cardiac surgery in patients with haemophilia

Abstract. Today the populations of haemophilia patients in many countries have a higher life expectancy than previously known, and age‐related disorders such as arterial disease are expected to become more prevalent, calling for surgical intervention. Cardiac surgery constitutes a major haemostatic challenge because of sternotomy, the need of total heparinization, extracorporal circulation, mild hypothermia and cardiac arrest. To evaluate our current experience and results with cardiac surgery in patients with haemophilia the present case series report on six patients with haemophilia A (Severe = 1, Moderate = 1, Mild = 4) undergoing cardiac surgery (coronary artery bypass grafting; CABG = 2, aortic valve replacement = 1, CABG + aortic valve replacement = 2, ventricular resection + mitral valve reconstruction = 1). The present paper provides detailed information on the haemostatic treatment regimens adopted (factor concentrate dosages, timing and duration) and postoperative thromboprophylaxis (dosing and duration of low molecular weight heparin). Moreover, we present data on concomitant disorders (hypertension, hypercholesterolaemia, atrial fibrillation and diabetes), left ventricle ejection fraction (30–60%), type of anaesthesia, total amount of heparin (34 500–53 500 IU) and duration of extracorporeal circulation (80–115 min). Clinical outcomes included: re‐operation because of bleeding (none), transfusion requirements, peri‐ and postoperative blood loss and complications and postoperative development of inhibitors (none). Clinical outcomes were compared with a control group of patients (n = 5993) without haemophilia and we found no difference in postoperative morbidity. Adopting meticulously supervised haemostatic treatment regimens, we have successfully performed major cardiac surgery in patients with haemophilia A. The clinical outcome as well as the severity and incidence of postoperative complications were similar to patients without haemophilia.     

Characteristics and management of the haemophilia‐associated pseudotumours

The management of haemophilia‐associated pseudotumours presents an ongoing challenge to the haematologist, surgeon and interventional radiologist alike. There is a range of therapeutic approaches including factor replacement, embolization, radiotherapy and a variety of surgical interventions. However, there remains little evidence regarding the most appropriate treatment. We aimed to evaluate the available options of management for the haemophilia‐associated pseudotumour. A literature review was performed using relevant terminology and reviewed for treatment approaches and outcomes. The results demonstrated that most of the data is from single case reports with a small number of single‐ and multicentre case series. In total, 133 patients with 134 described pseudotumours were identified. Adequate haemostatic control with factor replacement was a key component to successful treatment. Surgical excision was the most commonly reported surgical intervention with various composites used for filling of the surgical cavity. The use of radiotherapy has been described particularly in the paediatric population and sites of difficult surgical access. Embolization can be considered as a method of presurgical optimization. Patients with both factor inhibitors and pseudotumours have poorer postoperative outcomes. This review demonstrates that although a lack of large‐centre, randomized studies, timely surgical intervention with adequate haemostatic support and the consideration adjuvant therapies in selected cases can achieve acceptable outcomes in this cohort of patients.     

Continuous infusion of coagulation factor concentrates during intensive treatment

In clinical management of bleeds and surgical procedures in patients suffering from bleeding disorders either repetitive bolus injections (BI) or continuous infusion (CI) can be used for coagulation factor replacement. Continuous infusion seems to be an attractive route of administration and may be considered if replacement therapy is required for more than 3 days. The strongest argument favouring continuous infusion is its superiority in providing the patient with a safe and constant level of the deficient coagulation factor by balancing input with clearance. Furthermore, several studies have shown that coagulation factor consumption may be reduced by CI compared to repetitive bolus injections (BI) since unnecessary peaks of factor level are avoided. Concerns have been raised whether continuous infusion of coagulation concentrates is associated with an increased risk of developing inhibitors. However, available data have so far not shown an increased risk for inhibitor development in severe haemophilia patients with more than 50 exposure days of coagulation factor concentrates. Further, previously reported complications when using CI such as phlebitis at the infusion site and pump failure are nowadays very seldom seen when small amounts of heparin are added to the infusion bag, and increased quality of the pumps are available. Over the last decades, numerous reports have confirmed CI to be a safe and effective mode of coagulation factor replacement even in the most challenging surgical procedures, such as total joint arthroplasties.     

Analysis of low frequency bleeding data: the association of joint bleeds according to baseline FVIII activity levels

Summary. Many studies in the field of haemophilia and other coagulation deficiencies require analyses of bleeding frequencies. In haemophilia, the association of bleeding frequency with factor VIII (FVIII) activity levels is known from experience, but significant results are lacking. Bleeding frequencies in haemophilia are highly skewed count data, with large proportions of zeros. Both the skewness and the high amount of zeros pose a problem for standard (linear) modelling techniques. This study investigated the optimal analysing strategy for bleeding data by using the association of residual clotting factor level and number of joint bleeds in moderate and mild patients treated on demand as example. In total, 433 patients with moderate (27%) and mild (73%) haemophilia A treated on demand were included in this study. One year of self‐reported data on joint bleed frequency and baseline clotting factor activity were analysed using Poisson, negative binomial, zero‐inflated Poisson, and zero‐inflated negative binomial distributions. Multivariate regression analysis using negative binomial distribution provided the optimum data analytical strategy. This model showed 18% reduction [Rate ratio (RR) 0.82; 95%confidence interval (CI) 0.77–0.86] of bleeding frequency with every IU dL^‐1 increase in residual FVIII activity. The actual association is expected to be higher because of exclusion (30 out of 463 patients) of patients on prophylaxis (baseline FVIII levels 0.01–0.06 IU mL^?1). The best way to analyse low frequency bleeding data is using a negative binomial distribution.     

Efficacy assessment of a new clotting factor concentrate in haemophilia A patients, including prophylactic treatment

Summary.  Currently, efficacy of a new factor concentrate is mostly judged by its ability to achieve haemostasis after a bleeding episode. However, in patients on prophylaxis, the effectiveness in preventing bleeds, and thus joint damage, is most important. An albumin-free recombinant factor VIII (FVIII) concentrate was introduced in the Netherlands in 2004. In this study, the efficacy of a new recombinant plasma/albumin-free FVIII concentrate (rAHF-PFM, Advate®) was assessed by comparing bleeding frequency and factor consumption before and after switching to the new product, on both prophylactic and on-demand treatment. Eighty-two previously treated haemophilia A patients with  at least 1-year clinical follow-up were included in this study. Data on 410 patient-years were analysed, including 165 patient-years on other clotting factor products, and 245 patient-years on the new concentrate. In total, 19 628 368 IU of other factor concentrates were administered, to treat 839 bleeds, including 578 joint bleeds and cover 104 years of prophylactic treatment. For rAHF-PFM 33 082 250 IU FVIII, were used to treat 1144 bleeds, including 734 joint bleeds and cover 175 years of prophylactic treatment. No inhibitors, seroconversions or other serious adverse events were observed. Annual FVIII consumption per kg and annual number of joint bleeds before and after switching to the new albumin-free recombinant factor concentrate were similar in all patients. In conclusion, rAHF-PFM is equally effective as other clotting factor concentrates for prophylactic treatment in severe haemophilia.     

Prophylactic recombinant factor VIIa in haemophilia patients with inhibitors

Prevention of bleeding, especially into joints, with prophylactic factor infusions is the most effective treatment for severe haemophilia patients. Approximately 15-30% of patients with factor VIII deficiency and 3-5% of patients with factor IX deficiency develop neutralizing antibodies (inhibitors) to factor precluding their use. Such patients often have significant bleeding complications including life- and limb-threatening bleeds and severe joint disease. Prophylaxis for such patients is not generally considered because of the fact that the standard (bypassing) agents for such patients are not as effective as natural factor replacement, because of concerns for thrombotic complications and also because of the very high cost of bypassing agents. We treated two patients with high titre inhibitors with prophylactic recombinant factor VIIa (rFVIIa). The first patient was treated as a result of development of a target joint and to reduce the use of agents that can lead to anamnesis of his inhibitor. The second patient had multiple severe bleeds and was hospitalized 20% of the time over a 2-year period. He had a very poor quality of life. Both patients had shown good responses previously to rFVIIa for treatment of bleeds. Both patients had an outstanding response to prophylaxis albeit at a very high cost. Prophylaxis with rFVIIa can be an effective approach in select inhibitor patients with severe complications related to bleeding.     

Management of haemophilic pseudotumours with special emphasis on radiotherapy and arterial embolization

Summary.  The haemophilic pseudotumour is an expanding destructive haematoma, which is associated with a considerable amount of morbidity in haemophilic patients. Its prevention is paramount. In fact, this goal can be achieved by primary prophylaxis to avoid muscle haematomas and by adequate and long-term haematological treatment of muscle haematomas in case they appear. At the moment, surgical excision of pseudotumour is the preferred treatment by many authors. However, there are instances that surgical extraction of the lesion is not feasible. In such situations, radiotherapy and arterial embolization should be considered either alone or as an adjunct to surgery. Conservative management using a combination of radiotherapy and replacement therapy should be considered for treating haemophilic bone pseudotumours, which are located in the skull or in the distal parts of the limbs, especially in conditions where some impediments to surgical excision exist. In fact, the radiation should be delivered to the lesion site in small fragments of 2 Gy or less to a total dosage of 6–23.5 Gy, which is the most recommended radiation dosage, at the moment. Therapeutic arterial embolization of haemophilic pseudotumours should be considered in lesions of large size, especially in pseudotumours of pelvic region, as it may effectively reduce its size and decrease the risk of bleeding complications during surgery. Nevertheless, in view of its temporary effect, embolization may better be performed, as a preparatory procedure, at best about 2 weeks prior to surgery. This time lapse will allow for mass shrinkage but is insufficient for vessel restoration.     

Operative management and outcomes in children with congenital bleeding disorders: a retrospective review at a single haemophilia treatment centre

Establishing haemostasis for surgical procedures in children with inherited bleeding disorders is challenging. Providers are often hesitant to undertake surgeries in children with bleeding disorders out of fear of bleeding complications. To review the preoperative management and haemorrhagic complications of children with inherited bleeding disorders at our institution, we conducted a retrospective electronic medical record review from 1999 to 2010. Primary focus was review of bleeding complications and factor replacement strategies. A total of 168 procedures were performed in 66 children. Fifteen procedures (8%) in four children were performed in the presence of high-titre factor inhibitors. Procedures included central venous catheter (CVL) placement or revision (41%), otolaryngology procedures (23%), dental (11%), non-synovectomy orthopaedic procedures (8%), synovectomy (5%), circumcision (5%) and miscellaneous (7%). All patients received preoperative factor replacement (100% in haemophilia patients) followed by various factor replacement regimens postoperatively. No deaths or life-threatening bleeding occurred with any procedure. Twelve of 168 procedures (7%) were complicated by bleeding. Tonsillectomy was the most common procedure complicated by haemorrhage 4 of 15 (26%) followed by nasal surgery (3/7 bleeds = 43%). The CVL surgeries were remarkably free of complications with only 1/69 (1.4%) with bleeding. Surgical procedures are safe in children with bleeding disorders with adequate planning and factor replacement. Bleeding remains a problem in a subset of patients and requires ongoing haematological involvement and oversight. Delayed bleeding following T&A was especially common and suggests a need for close follow-up and ongoing factor coverage for this group of patients.     

A 6-year follow-up of dosing, coagulation factor levels and bleedings in relation to joint status in the prophylactic treatment of haemophilia

Summary. The primary aim of this study was to investigate the possible relationship between coagulation factor level and bleeding frequency during prophylactic treatment of haemophilia after stratification of the patients according to joint scores. The secondary aim was to obtain a systematic overview of the doses of coagulation factors prescribed for prophylaxis at the Malmö haemophilia treatment centre during a 6‐year period. A retrospective survey of medical records for the years 1997–2002 and pharmacokinetic study results from the 1990s was complemented by collection of blood samples for coagulation factor assay when needed. Information on the dosing and plasma levels of factor VIII or factor IX, joint scores and incidence of bleedings (joint bleeds and ‘other bleeds’) was compiled. The patients were stratified by age (0–6, 7–12, 13–18, 19–36 and >36 years) and joint score (0, 1–6 and >6). Individual pharmacokinetic parameters of plasma coagulation factor activities (FVIII:C and FIX:C) were estimated. Trough levels during the treatment were calculated, as well as the number of hours per week of treatment during which plasma FVIII:C/FIX:C fell below a 1, 2 or 3% target level. Fifty‐one patients with haemophilia A (two moderate, 49 severe) and 13 with haemophilia B (all severe) were included, yielding data for 364 patient‐years of treatment. There was a wide range of dosing schedules, the most common ones being three times a week or every other day for FVIII and twice a week or every third day for FIX. The overall relationship between FVIII:C/FIX:C levels and incidence of joint bleeding was very weak, even after stratification of the patients according to joint score. There was no relationship between coagulation factor level and incidence of other bleeds. In this cohort of patients on high‐dose prophylactic treatment, dosing was based more on clinical outcome in terms of bleeding frequency than on the aim to maintain a 1% target level of FVIII:C/FIX:C. Some patients did not bleed in spite of a trough level of <1% and others did in spite of trough levels >3%. The practical implication of our findings is that dosing in prophylactic treatment of haemophilia should be individualized. Thus, proposed standard regimens should be implemented only after careful clinical consideration, with a high readiness for re‐assessment and individual dose tailoring.     

A comparison between prophylaxis and on demand treatment for severe haemophilia

Patients with severe haemophilia can be treated for bleeding either prophylactically or on demand. Each treatment modality has advantages and disadvantages from both a medical and economic point of view. This study aims to find which modality requires more units of clotting factors per body weight per year and to compare the number of bleeds between the two. The study sample consisted of 133 patients with severe haemophilia A and B treated in the Katharine Dormandy Haemophilia Centre at the Royal Free Hampstead NHS Trust in London. The average number of clotting factors used per body weight per year was 2181.7 units for prophylaxis vs. 711 units for on demand treatment (P = 0.000). Although more units used means more money spent, and although prophylaxis has additional complications, namely venipunctures and increased risk of viral contamination, other criteria must be considered including the total number of bleeds and health-related quality of life. The total number of bleeds per year was significantly (P = 0.021) less for prophylactically (7.4) vs. on-demand treated patients (11.4). This suggests that prophylaxis reduces the risk of arthropathies, the number of future hospital visits and orthopaedic surgeries, and is thus the optimal modality of treatment for patients with severe haemophilia.     

Changes in treatment strategies for severe haemophilia over the last 3 decades: effects on clotting factor consumption and arthropathy

A cohort study was performed among 214 patients with severe haemophilia, born 1944-1994, to describe changes in treatment over the last 3 decades and its effects on clotting factor consumption and haemophilic arthropathy. Data on treatment strategy, clotting factor consumption, and outcome were collected for 3567 patient years (from 1972 to 1998), and 493 Pettersson scores were analysed. Median follow up was 17 years (range 6-27 years), and median age in 1998 was 27.6 years. Since 1965, replacement therapy, prophylaxis, and home treatment have been used and treatment intensified. Over the last 3 decades, annual clotting factor consumption increased by 260%, for both prophylactic and on-demand treatment. Annual clotting factor consumption kg-1 increased during childhood and appeared to stabilize in early adulthood for patients born 1965-79, who were treated with early replacement therapy or early prophylaxis. In contrast, clotting factor consumption increased continuously for patients born before 1965, who had had no access to replacement therapy during the early years of their life. The annual number of joint bleeds decreased over the years. Arthropathy as measured by the Pettersson score generally became apparent around the age of 15 years and was lowest in patients treated with primary prophylaxis. In conclusion, clotting factor consumption has increased and haemophilic arthropathy has decreased due to the intensification of treatment for severe haemophilia over the last 3 decades. Annual clotting factor consumption stabilizes in adulthood for patients who receive early intensive treatment.     

Haemophilia B: Where are we now and what does the future hold?

Research has been lacking on the natural history, complications, and treatment of haemophilia B, which is less common than haemophilia A and was recognized as a distinct clinical entity in 1947. Although the two diseases share the same clinical manifestations, they differ in causative mutation, risk of inhibitor development, and patient quality of life. Frequently debated is whether haemophilia B is as clinically severe as haemophilia A, with much of the published data on overall and haemophilia-specific health outcomes suggesting that haemophilia B may have a less severe clinical phenotype. However, although fewer haemophilia B than haemophilia A patients appear to experience bleeding, bleeds are just as severe. We review distinguishing characteristics of haemophilia B and its treatment, including management strategies for neonates, therapeutic approaches for patients who develop inhibitors, pharmacokinetics of factor IX concentrates administered as replacement therapy, and potential future treatments.