Hemophilia is the most common, severe, inherited bleeding disorder recognized in humans and makes up the largest proportion of patients followed in most bleeding disorders' clinics. Persons with ...hemophilia have a life-long bleeding tendency that roughly correlates to their endogenous coagulant factor VIII (FVIII) or factor IX (FIX) level (FVIII:C and FIX:C). The hallmark of bleeding in severe hemophilia is musculoskeletal bleeds (soft tissue, muscle and joint bleeds) but persons with hemophilia are also prone to other bleeds including intracranial bleeds. The neonatal period is a particularly vulnerable period for persons with severe hemophilia. Diagnosing hemophilia is mainly based on measuring FVIII:C and FIX:C levels and on distinguishing hemophilia from other conditions that can cause a low FVIII:C or FIX:C level. Management involves preventing bleeds and rapidly treating those that occur. Bleed prevention in severe hemophilia can be accomplished by avoiding high-risk activities, taking appropriate precautions and early commencement of life-long prophylaxis. With proper management, persons with severe hemophilia can now live an essentially normal life. The development of an inhibitor does however complicate management. This review will summarize the very complex and multifaceted aspects of diagnosing and managing persons with hemophilia.
Prophylactic replacement of factor concentrate is the established optimal treatment to avoid or minimize joint disease in severe hemophilia patients, thus ultimately improving their life expectancy ...and quality of life toward values matching those in the normal population. Where uncertainty still exists is around the optimal regimen to be prescribed for prophylaxis, and more and more treaters and patients are showing interest in patient tailored approaches to prophylaxis, aiming at matching the prophylaxis regimen to the specific needs of the patient. The rationale behind tailoring the prophylaxis regimen to the individual patient is based on the significant variability that exists between patients (all with the same label of severe hemophilia) with respect to their bleeding phenotype, their pharmacokinetic handling of factor, their levels of physical activity, and a variety of other characteristics that contribute to differential prophylaxis needs of patients. Of course, any form of tailoring of prophylaxis needs to take into consideration the economic resources of the country; for many countries very intense prophylaxis regimens are just not possible. This article will review different concerns and strategies when tailoring prophylaxis, and will address how these issues will apply to the new longer acting factor concentrates in development.
Factor VIII (FVIII) pharmacokinetic (PK) properties show high interpatient variability in hemophilia A patients. Although previous studies have determined that age, body mass index, von Willebrand ...factor antigen (VWF:Ag) levels, and ABO blood group status can influence FVIII PK, they do not account for all observed variability. In this study, we aim to describe the genetic determinants that modify the FVIII PK profile in a population of 43 pediatric hemophilia A patients. We observed that VWF:Ag and VWF propeptide (VWFpp)/VWF:Ag, but not VWFpp, were associated with FVIII half-life. VWFpp/VWF:Ag negatively correlated with FVIII half-life in patients with non-O blood type, but no correlation was observed for type O patients, suggesting that von Willebrand factor (VWF) half-life, as modified by the ABO blood group, is a strong regulator of FVIII PK. The FVIII-binding activity of VWF positively correlated with FVIII half-life, and the rare or low-frequency nonsynonymous VWF variants p.(Arg826Lys) and p.(Arg852Glu) were identified in patients with reduced VWF:FVIIIB but not VWF:Ag. Common variants at the VWF, CLEC4M, and STAB2 loci, which have been previously associated with plasma levels of VWF and FVIII, were associated with the FVIII PK profile. Together, these studies characterize the mechanistic basis by which VWF clearance and ABO glycosylation modify FVIII PK in a pediatric population. Moreover, this study is the first to identify non-VWF and non-ABO variants that modify FVIII PK in pediatric hemophilia A patients.
•VWF gene variants that modify FVIII binding influence FVIII PK.•Variants in clearance receptors for VWF-FVIII influence FVIII PK.
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Background Mixed autoimmune hemolytic anemia (AIHA) shows combined clinical and laboratory characteristics of warm and cold AIHA. It is relatively uncommon in children. Consequently, knowledge about ...mixed AIHA prevalence, clinical presentation, treatment options, and prognosis in children is limited to very few case reports. Case presentation We describe a six-year-old Asian girl presenting with profound anemia, blood group typing discrepancy and crossmatch incompatibility, post upper respiratory tract infection. Detection of red cell warm and cold reactive autoantibodies, led to the diagnosis of mixed AIHA. Autoantibodies with laboratory evidence of hemolysis persisted despite high dose steroid therapy. Due to the inability to wean further, the patient was subsequently commenced on mycophenolate mofetil to which she seems to be responding. Conclusions Mixed AIHA may be notoriously difficult to diagnose and treat. Detailed clinical and laboratory work-up is essential to establish the diagnosis. To the best of our knowledge, this is the first case report of mixed AIHA following upper respiratory tract infection. Awareness of this occurrence is important, as similar to warm AIHA, mixed AIHA should be treated immediately by early initiation of steroid therapy. In addition, prompt supportive care as well as long-term clinical follow-up are required to improve outcomes of these cases. Keywords: Autoimmune hemolytic anemia (AIHA), Mixed autoimmune hemolytic anemia, Warm and cold autoantibodies, Case report, Pediatric
Hemophilia in a Changing Treatment Landscape Pelland-Marcotte, Marie-Claude; Carcao, Manuel D
Hematology/oncology clinics of North America,
06/2019, Volume:
33, Issue:
3
Journal Article
Peer reviewed
The mainstay of hemophilia management has been the regular, prophylactic infusion of missing coagulation factors VIII/IX. This approach is limited by the need for frequent intravenous infusions, high ...cost, limited availability, and the development of inhibitory antibodies to factors VIII/IX. Numerous recent breakthroughs are addressing many of these limitations. These include the development of extended half-life factors that require less frequent infusions and the development of various novel agents that can be given subcutaneously and infrequently, including FVIII-mimetic antibody and downregulators of natural anticoagulants. Finally, gene therapy is set to offer patients a possibility for a cure.
Summary
Hereditary spherocytosis (HS) is a common inherited haemolytic anaemia attributed to disturbances in five different red cell membrane proteins. We performed a retrospective study of 166 ...children with HS and describe the clinical phenotype according to the genotype. In 160/166 (97%) children with HS a disease‐causing mutation was identified. Pathogenic variants in ANK1, SPTB, SLC4A1 and SPTA1 were found in 49%, 33%, 13% and 5% of patients. Children with SLC4A1‐HS had the mildest phenotype, showing the highest haemoglobin (P < 0·001), lowest reticulocyte counts (P < 0·001) and lowest unconjugated bilirubin levels (P = 0·006), and none required splenectomy in childhood (P < 0·001). Conversely, children with autosomal recessive SPTA1‐HS had the most severe clinical phenotype, with almost all patients undergoing splenectomy in early childhood. Patients with ANK1 and SPTB variants showed a similar clinical phenotype. Within each gene, variant type or location did not predict disease severity or likelihood of splenectomy. Among patients with a genetic diagnosis, 47 (29%) underwent splenectomy (23 partial; 24 total) while 57 (36%) underwent cholecystectomy. Total splenectomy led to greater improvements in haemoglobin (P = 0·02). Select use of genetic testing (especially in patients without a family history) may help predict clinical phenotype in childhood and guide family counselling.
Homozygosity/compound heterozygosity for loss of function mutations in neurobeachin-like 2 (NBEAL2) is causative for Gray platelet syndrome (GPS; MIM #139090), characterized by thrombocytopenia and ...large platelets lacking α-granules and cargo. Most GPS-associated NBEAL2 mutations generate nonsense codons; frameshifts causing premature translation termination and/or changes in mRNA splicing have also been observed. Data regarding NBEAL2 protein expression in GPS patients is limited. We observed absence of NBEAL2 in platelets from GPS patients with 3 different genotypes, and reduced/truncated platelet NBEAL2 has been reported for others. GPS is commonly associated with mild bleeding, but lifethreatening bleeding has been reported in some cases. A common long-term complication in GPS patients is myelofibrosis; splenomegaly is less common but sometimes of sufficient severity to merit splenectomy. Like GPS patients, mice lacking NBEAL2 expression exhibit macrothrombocytopenia, deficiency of platelet α-granules, splenomegaly, myelofibrosis, impaired platelet function and abnormalities in megakaryocyte development. Animal studies have also reported impaired platelet function in vivo using laser injury and thrombo-inflammation models. NBEAL2 is a large gene with 54 exons, and several putative functional domains have been identified in NBEAL2, including PH (pleckstrin homology) and BEACH (beige and Chediak-Higashi) domains shared with other members of a protein family that includes LYST and LRBA, also expressed by hematopoietic cells. Potential NBEAL2-interacting proteins have recently been identified, and it is expected that current and future efforts will reveal the cellular mechanisms by which NBEAL2 facilitates platelet development and supports hemostatic function.
Introduction
The genetic variant responsible for haemophilia A (HA) significantly impacts endogenous coagulant factor VIII (FVIII:C) level, thus impacting DDAVP responsiveness. Blood group (BG) also ...impacts FVIII:C levels, but this is difficult to evaluate in a genetically heterogeneous population. Canada has a large cohort of mild‐moderate HA due to a single point variant: c.6104T>C, p.Val2035Ala—the Twillingate variant.
Aim
To evaluate the impact of BG on endogenous FVIII:C levels and DDAVP responsiveness in a single genotype of mild‐moderate HA.
Methods
This was a retrospective, single‐centre study. BG and FVIII:C levels were obtained for males with the Twillingate variant. One‐hour absolute and fold increases in FVIII:C post‐DDAVP were calculated. T‐tests and Mann–Whitney U tests were used to compare FVIII:C levels and DDAVP challenge variables between individuals according to BGs (O vs. non‐O).
Results
Twenty males were included. There were significant differences between BGs (O vs. non‐O) in their lowest FVIII:C level at age <12 years (medians: 0.05 vs. 0.08 IU/mL; P = .05). Fifteen subjects underwent DDAVP challenges. Mean 1‐h FVIII:C were 0.29 (O BG) versus 0.41 IU/mL (non‐O BG); P = .04. There were no significant differences between BGs (O vs. non‐O) in mean absolute FVIII:C increase (0.20 vs. 0.27 IU/mL; P = .10) and FVIII:C fold increase (3.3‐fold vs. 3.8‐fold; P = .51).
Conclusion
In HA subjects with an identical genotype, BG significantly impacts baseline FVIII:C levels and FVIII:C levels post‐DDAVP, but does not impact absolute and fold increases in FVIII:C with DDAVP.
Congenital factor XIII (FXIII) deficiency is a rare, autosomal-recessive disorder, with most patients having an A-subunit (FXIII-A) deficiency. Patients experience life-threatening bleeds, impaired ...wound healing, and spontaneous abortions. In many countries, only plasma or cryoprecipitate treatments are available, but these carry a risk for allergic reactions and infection with blood-borne pathogens. The present study was a multinational, open-label, single-arm, phase 3 prophylaxis trial evaluating the efficacy and safety of a novel recombinant FXIII (rFXIII) in congenital FXIII-A subunit deficiency. Forty-one patients ≥ 6 years of age (mean, 26.4; range, 7-60) with congenital FXIII-A subunit deficiency were enrolled. Throughout the rFXIII prophylaxis, only 5 bleeding episodes (all trauma induced) in 4 patients were treated with FXIII-containing products. The crude mean bleeding rate was significantly lower than the historic bleeding rate (0.138 vs 2.91 bleeds/patient/year, respectively) for on-demand treatment. Transient, non-neutralizing, low-titer anti-rFXIII Abs developed in 4 patients, none of whom experienced allergic reactions, any bleeds requiring treatment, or changes in FXIII pharmacokinetics during the trial or follow-up. These non-neutralizing Abs declined below detection limits in all 4 patients despite further exposure to rFXIII or other FXIII-containing products. We conclude that rFXIII is safe and effective in preventing bleeding episodes in patients with congenital FXIII-A subunit deficiency. This study is registered at http://www..clinicaltrials.gov as number NCT00713648.
Essentials
The PK parameters of Eloctate vs Adynovate were compared using one‐stage and chromogenic assays in 25 boys (12‐18 years).
The FVIII levels were taken at 3, 24, 48, and 72 hours following a ...dose of either FVIII; levels analyzed by WAPPS PK program.
The PK profiles (half‐life, clearance, and time to 5%, 3%, and 1%) were not statistically different for the two EHL FVIIIs.
The significant interpatient variability in PK is mainly related to VWF levels (and blood group).
Background
A head‐to‐head comparison of the pharmokinetcs (PK) of extended half‐life (EHL) factor VIII (FVIII) concentrates in the same subjects has not been reported. Recently, boys (ages 12‐18 years) with hemophilia A in Canada were required to switch from Eloctate to Adynovate.
Objectives
Compare the PK profiles of Eloctate vs Adynovate in the same boys.
Methods
Boys switching from Eloctate to Adynovate prophylaxis had FVIII levels sampled at 3, 24, 48, and 72 hours following a regular prophylactic infusion of Eloctate and then 1‐3 months later, of Adynovate. Testing was done by one‐stage assay (OSA) and chromogenic assay (CA). The PK parameters were determined with the Web Accessible Population Pharmacokinetic Service (WAPPS)–Hemo PK tool.
Results
Twenty‐five boys (mean age 15.3 years; range: 12.1‐18.4; 9 O blood group) underwent switching. Mean (range) terminal half‐lives with the OSA were 16.1 hours (10.4 to 23.4; Eloctate) and 16.7 hours (11.0 to 23.6; Adynovate) (NS). With the CA, these were 18.0 hours (12.0 to 25.5; Eloctate) and 16.0 hours (10.3 to 22.9; Adynovate) (P = 0.001). There were no significant differences between the two EHL‐FVIIIs in clearance, area under the concentration vs time curve (AUC), Vss, or time for FVIII levels to drop to 5%, 3%, and 1%. At the 72‐h time point, mean observed FVIII levels following a mean dose of 39.3 IU/kg of Eloctate were 4.4% (OSA) and 4.4% (CA). For Adynovate, these were 5.1% (OSA) and 5.3% (CA) following similar doses. There was considerable interpatient variation in PK, mainly explained by differences in blood group/von Willebrand factor (VWF) levels.
Conclusions
Eloctate and Adynovate have almost identical PK parameters. When switching from one to another no prophylaxis regimen change is needed.
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