Severe haemorrhages leading to a diagnosis of rare bleeding disorder occur at a very young age: A study from the FranceCoag network.

INTRODUCTION: In the context of severe unexplained haemorrhage (SH), it is usual to seek haematological evaluation and investigate for an inherited rare bleeding disorder (IRBD). In such circumstances, appropriate screen can discriminate between IRBD and suspected child abuse. Yet, little information is available about the frequency of SH in the population of patients with IRBD. AIM: To collect epidemiologic data about SH and IRBD. METHOD: The database of the FranceCoag network has collected information about IRBD since January 2004. Based on data gathered up to 16 March 2022, a retrospective search was conducted for of SH events having occurred before or at the time of IRBD diagnosis. Demographics and diagnosis circumstances were retrieved, as well as information about SH, defined as any life-threatening bleeding or intracranial haemorrhage. RESULTS: Among the 13,433 patients of the database, 109 (0.8%) fulfilled inclusion criteria including a known date of IRBD diagnosis, haemophilia A or B (HA/HB) being the most frequent (82.5%). IRBD was discovered as a consequence of an SH event in 82.6% of the cases while CNS was involved in 55%. Severe and moderate HA/HB and other severe IRBD presented significantly more intracranial haemorrhage (p < .02) and a lower age at diagnosis (p = .03). CONCLUSIONS: These data support that any unusual SH should raise a suspicion of IRBD. Particularly before 1-year of age, it is suggested to first confirm moderate or severe haemophilia and severe IRBD by standard coagulation tests (APTT, PT and fibrinogen), combined with a clotting FXIII assay as first-line investigation. Subsequent assays of coagulation factors should be performed in the case of abnormal values, in second-line investigation.

Pubertal development of transfusion-dependent thalassemia patients in the era of oral chelation with deferasirox: results from the French registry.

Not available.

In vitro characterization of rare anti-αIIbß3 isoantibodies produced by patients with Glanzmann thrombasthenia that severely block fibrinogen binding and generate procoagulant platelets via complement activation.

Background: Glanzmann thrombasthenia (GT) is a rare bleeding disorder caused by inherited defects of the platelet αIIbß3 integrin. Platelet transfusions can be followed by an immune response that can block integrin function by interfering with fibrinogen binding. Objectives: In this study, we aimed to determine the prevalence of such isoantibodies and better characterize their pathogenic properties. Methods: Twelve patients with GT were evaluated for anti-αIIbß3 isoantibodies. Sera from patients with GT with or without anti-αIIbß3 isoantibodies were then used to study their in vitro effect on platelets from healthy donors. We used several approaches (IgG purification, immunofluorescence staining, and inhibition of signaling pathways) to characterize the pathogenic properties of the anti-αIIbß3 isoantibodies. Results: Only 2 samples were able to severely block integrin function. We observed that these 2 sera caused a reduction in platelet size similar to that observed when platelets become procoagulant. Mixing healthy donor platelets with patients' sera or purified IgGs led to microvesiculation, phosphatidylserine exposure, and induction of calcium influx. This was associated with an increase in procoagulant platelets. Pore formation and calcium entry were associated with complement activation, leading to the constitution of a membrane attack complex (MAC) with enhanced complement protein C5b-9 formation. This process was inhibited by the complement 5 inhibitor eculizumab and reduced by polyvalent human immunoglobulins. Conclusion: Our data suggest that complement activation induced by rare blocking anti-αIIbß3 isoantibodies may lead to the formation of a MAC with subsequent pore formation, resulting in calcium influx and procoagulant platelet phenotype.

Acquired haemophilia A in paediatric patients: A retrospective French cohort of eight cases.

Acquired haemophilia A (AHA) is a rare haemorrhagic disease characterised by new-onset haemorrhagic symptoms associated with a dramatic decrease in factor VIII levels and an anti-factor VIII neutralising autoantibody concentration >0.6 Bethesda units. Elderly people are often affected, whereas children are rarely affected; the paediatric incidence reported in the literature is about 0.045 case/million/year. For some time, the paediatric standard of care has been that for adults, but clinicians have often reported poor outcomes. Here, we describe the largest retrospective paediatric AHA cohort assembled to date, including eight patients diagnosed in France from 2000 to 2020.

Determinants of adherence and consequences of the transition from adolescence to adulthood among young people with severe haemophilia (TRANSHEMO): A multicentric French national observational cross-sectional study based on the FranceCoag registry.

INTRODUCTION: It is necessary to gain insights into adherence to healthcare in people with severe haemophilia (PwSH), especially during the transition from paediatric to adult care, which is an important phase in lives of young people with childhood chronic disease. This adherence can be considered as a marker of successful transition. OBJECTIVES: The main objective of the quantitative phase of the TRANSHEMO project was to compare the adherence to healthcare between adolescents and young adults (YAs) with severe haemophilia. The secondary objective was to identify the determinants (facilitators and barriers) of this adherence and associations between these determinants. METHODS: A multicentre, observational, cross-sectional study was conducted in 2017-2019 on PwSH aged between 14 and 17 years (adolescents) or between 20 and 29 years (YAs), included in the FranceCoag registry and having completed the questionnaires. The adherence to healthcare (treatment regimens and clinical follow-up) was compared between adolescents and YAs using the chi-squared test. The determinants of this adherence were analysed by structural equation modelling. RESULTS: There were 277 participants, 107 adolescents, and 170 YAs. The rate of adolescents adhering to healthcare was 82.2%, while the rate of YAs was 61.2% (p < .001). The barriers to the adherence to healthcare were being YA, having repeated at least one school grade and presenting mental health concerns. CONCLUSION: Adolescents had better adherence to healthcare than YAs. According to the determinants enlightened in this project, targeted supportive strategies and adapted therapeutic education programs can be developed for young PwSH to facilitate their adherence to healthcare.

Whole F8 gene sequencing combined with splicing functional analyses led to a substantial increase of the molecular diagnosis yield for non-severe haemophilia A.

INTRODUCTION: Conventional genetic investigation fails to identify the F8 causal variant in 2.5%-10% of haemophilia A (HA) patients with non-severe phenotypes. In these cases, F8 deep intronic variants could be causal. AIM: To identify pathogenic F8 deep intronic variants in genetically unresolved families with non-severe HA analysed in the haematology laboratory of the Hospices Civils de Lyon. METHODS: The whole F8 was analysed by next generation sequencing. The pathogenic impact of candidate variants identified was assessed using both in silico analysis (MaxEntScan and spliceAI) and functional analysis (RNA or minigene assay). RESULTS: Sequencing was performed in 49/55 families included for which a DNA sample from a male propositus was available. In total, 33 candidate variants from 43 propositi were identified. These variants corresponded to 31 single nucleotide substitutions, one 173-bp deletion, and an 869-bp tandem triplication. No candidate variant was found in six propositi. The most frequent variants found were the association of [c.2113+1154G>C and c.5374-304C>T], identified in five propositi, and the c.2114-6529C>G identified in nine propositi. Four variants had been previously described as HA-causing. Splicing functional assay found a deleterious impact for 11 substitutions (c.671-94G>A, c.788-312A>G, c.2113+1154G>C, c.2114-6529C>G, c.5999-820A>T, c.5999-786C>A, c.5999-669G>T, c.5999-669G>A, c.5999-669G>C, c.6900+4104A>C, and c.6901-2992A>G). The HA-causing variant was identified in 33/49 (67%) cases. In total, F8 deep intronic variants caused 8.8% of the non-severe HA among the 1643 families analysed in our laboratory. CONCLUSION: The results emphasise the value of whole F8 gene sequencing combined with splicing functional analyses to improve the diagnosis yield for non-severe HA.

High Rates of Anti-αIIbß3 Antibodies Produced by a Glanzmann Thrombasthenia Patient after First and Unique Red Blood Cells Administration.

Immunization against the platelet αIIbß3 glycoprotein due to blood transfusion represents one of the most severe complications in Glanzmann thrombasthenia (GT) disease. Anti-αIIbß3 isoantibodies development may lead to ineffective platelet transfusion and can, in case of pregnancy, cross the placenta leading to fetal thrombocytopenia. We describe here the case of a girl with type I GT who developed high rates of anti-αIIbß3 isoantibodies after first and unique blood transfusion. Surprisingly, this patient had only received red blood cell concentrates and immunization was presumably stimulated by the residual presence of platelets in concentrates. This study emphasizes the need for regular anti-αIIbß3 antibodies screening in GT, even though patients have never been previously transfused with platelet concentrates.

A new case with Hermansky-Pudlak syndrome type 9, a rare cause of syndromic albinism with severe defect of platelets dense bodies.

Hermansky-Pudlak syndrome (HPS) is a rare form of syndromic oculocutaneous albinism caused by disorders in lysosome-related organelles. Ten genes are associated with different forms of HPS. HPS type 9 (HPS-9) is caused by biallelic variants of BLOC1S6. To date, only three patients with HPS-9 have been reported. We described one patient presenting with ocular features of albinism. Genetic analysis revealed two compound heterozygous variants in the BLOC1S6 gene. Extended hematological studies confirmed the platelet storage pool disease with absence of dense granules and abnormal platelet aggregation. By reviewing the previous published cases we confirm the phenotype of HPS-9 patients. This patient is the only one described with dextrocardia and abnormal psychomotor development.

Immunization against αIIb ß3 and αv ß3 in Glanzmann thrombasthenia patients carrying the French Gypsy mutation.

Essentials The c.1544+1G>A mutation was identified in Gypsy Glanzmann thrombasthenia (GT) patients. Gypsy GT patients express normal αv ß3 carrying HPA-1b epitopes. To demonstrate HPA-1a alloimmunization by modified antigen capture assays. Gypsy GT patients could develop anti-HPA-1a alloantibodies against ß3 and αv ß3 . ABSTRACT: Background Glanzmann thrombasthenia (GT) is a rare bleeding disorder caused by the absence or the dysfunction of the platelet αIIb ß3 integrin. A founder mutation in the ITGA2B gene was previously identified in French Gypsy patients. Interestingly, this mutation was strongly linked to the human platelet antigen-1b (HPA-1b). The HPA-1bb Gypsy patients are at risk of isoimmunization against αIIb ß3 , as this complex is not expressed at their platelet surface. Tentatively, they would, however, not have an increased risk of developing anti-HPA-1a alloantibodies by exposure of αIIb ß3 on platelets from random platelet transfusions. However, the ß3 chain can also associate with the αv subunit expressed at the platelet surface. Because Gypsy GT patients express normal αv ß3 carrying HPA-1b epitopes, these patients might develop anti-HPA-1a alloantibodies reacting with αv ß3 and/or ß3 . Objectives/Patients/Methods To demonstrate this hypothesis, sera from HPA-1bb (n = 5) and HPA-1ab (n = 1) Gypsy GT patients were investigated by modified antigen capture assay using platelets or stable transfected cells. Furthermore, stable transfected cells expressing either αIIb ß3 or αv ß3 together with soluble monomeric chimeric ß3 (as absorbent) were used to differentiate anti-ß3 and anti-αv ß3 reactivity. Results Only HPA-1bb patients developed alloantibodies reacting with HPA-1a cells. Further analysis showed that HPA-1bb patients developed anti-HPA-1a alloantibodies reacting with ß3 and/or αv ß3 . Conclusion In this study, we found that HPA-1bb patients who failed to express αIIb ß3 on the platelet surface can develop alloantibodies against HPA-1a reacting with ß3 as well as αv ß3 . This is of particular importance as anti-HPA-1a alloantibodies might cause fetal neonatal alloimmune thrombocytopenia and/or platelet transfusion refractoriness.

A novel rare c.-39C>T mutation in the PROS1 5'UTR causing PS deficiency by creating a new upstream translation initiation codon.

Autosomal dominant inherited Protein S deficiency (PSD) (MIM 612336) is a rare disorder caused by rare mutations, mainly located in the coding sequence of the structural PROS1 gene, and associated with an increased risk of venous thromboembolism. To identify the molecular defect underlying PSD observed in an extended French pedigree with seven PSD affected members in whom no candidate deleterious PROS1 mutation was detected by Sanger sequencing of PROS1 exons and their flanking intronic regions or via an multiplex ligation-dependent probe amplification (MLPA) approach, a whole genome sequencing strategy was adopted. This led to the identification of a never reported C to T substitution at c.-39 from the natural ATG codon of the PROS1 gene that completely segregates with PSD in the whole family. This substitution ACG→ATG creates a new start codon upstream of the main ATG. We experimentally demonstrated in HeLa cells that the variant generates a novel overlapping upstream open reading frame (uORF) and inhibits the translation of the wild-type PS. This work describes the first example of 5'UTR PROS1 mutation causing PSD through the creation of an uORF, a mutation that is not predicted to be deleterious by standard annotation softwares, and emphasizes the need for better exploration of such type of non-coding variations in clinical genomics.

Determinants of adherence and consequences of the transition from adolescence to adulthood among young people with severe haemophilia (TRANSHEMO): study protocol for a multicentric French national observational cross-sectional study.

INTRODUCTION: Severe haemophilia is a rare disease characterised by spontaneous bleeding from early childhood, which may lead to various complications, especially in joints. It is nowadays possible to avoid these complications thanks to substitutive therapies for which the issue of adherence is major. The transition from adolescence to adulthood in young people with severe haemophilia is a critical period as it is associated with a high risk of lack of adherence to healthcare, which might have serious consequences on daily activities and on quality of life. METHODS AND ANALYSIS: We present the protocol for a cross-sectional, observational, multicentric study to assess the differences between adolescents and young adults with severe haemophilia in France through the transition process, especially on adherence to healthcare. This study is based on a mixed methods design, with two complementary and consecutive phases, comparing data from a group of adolescents (aged 14-17 years) with those from a group of young adults (aged 20-29 years). The quantitative phase focuses on the determinants (medical, organisational, sociodemographic and social and psychosocial and behavioural factors) of adherence to healthcare (considered as a marker of the success of transition). The qualitative phase explores participants' views in more depth to explain and refine the results from the quantitative phase. Eligible patients are contacted by the various Haemophilia Treatment Centres participating in the French national registry FranceCoag. ETHICS AND DISSEMINATION: The study was approved by the French Ethics Committee and by the French National Agency for Medicines and Health Products Safety (number: 2016-A01034-47). Study findings will be disseminated to the scientific and medical community in peer-reviewed journals and presented at scientific meetings. Results will be popularised to be communicated via the French association for people with haemophilia to participants and to the general public. TRIAL REGISTRATION NUMBER: NCT02866526; Pre-results.

Analyses of the FranceCoag cohort support differences in immunogenicity among one plasma-derived and two recombinant factor VIII brands in boys with severe hemophilia A.

Around one third of boys with severe hemophilia A develop inhibitors (neutralizing antibodies) against their therapeutic factor VIII product. This adverse effect may result in more life-threatening bleeding, disability, impaired quality of life, and costly care. We compared the incidence of inhibitors in boys treated with the three factor VIII products most used in France: one plasma-derived (Factane) and two recombinant products (Advate and Kogenate Bayer). A previously untreated cohort of patients was created in 1994 to investigate risk factors for inhibitor development. We selected boys with severe hemophilia A (factor VIII <1 IU/dL) first treated with one of the three factor VIII products studied. Details of product infusions, inhibitor assays and main fixed and time-varying inhibitor risk factors were recorded for the first 75 exposure days. Three outcomes (all inhibitors, high-titer inhibitors and subsequently treated inhibitors) were analyzed by univariate and multivariate Cox models. We studied 395 boys first treated between 2001 and 2016 (131, 137, and 127 with Factane, Advate, and Kogenate Bayer, respectively). Clinically significant inhibitors were diagnosed in 121 patients (70 high-titer). The incidence of high-titer inhibitors was significantly associated with the factor VIII product received (P=0.005): the cumulative incidence at 75 exposure days was 12.7% (95% CI: 7.7-20.6) with Factane, 20.4% (95% CI: 14.0-29.1) with Advate, and 31.6% (95% CI: 23.5-41.7) with Kogenate Bayer. The low inhibitor incidence observed with Factane is concordant with recent findings from the SIPPET randomized trial. These consistent results from observational and experimental studies should lead to improved care for previously untreated patients and cost savings for healthcare systems worldwide.