A GP1BA Variant in a Czech Family with Monoallelic Bernard-Soulier Syndrome

Bernard-Soulier syndrome (BSS) is a rare inherited disorder characterized by unusually large platelets, low platelet count, and prolonged bleeding time. BSS is usually inherited in an autosomal recessive (AR) mode of inheritance due to a deficiency of the GPIb-IX-V complex also known as the von Willebrand factor (VWF) receptor. We investigated a family with macrothrombocytopenia, a mild bleeding tendency, slightly lowered platelet aggregation tests, and suspected autosomal dominant (AD) inheritance. We have detected a heterozygous GP1BA likely pathogenic variant, causing monoallelic BSS. A germline GP1BA gene variant (NM_000173:c.98G > A:p.C33Y), segregating with the macrothrombocytopenia, was detected by whole-exome sequencing. In silico analysis of the protein structure of the novel GPIbα variant revealed a potential structural defect, which could impact proper protein folding and subsequent binding to VWF. Flow cytometry, immunoblot, and electron microscopy demonstrated further differences between p.C33Y GP1BA carriers and healthy controls. Here, we provide a detailed insight into its clinical presentation and phenotype. Moreover, the here described case first presents an mBSS patient with two previous ischemic strokes.

Successful pregnancy and delivery management in a patient with Bernard Soulier Syndrome

Bernard Soulier Syndrome (BSS) is an inherited bleeding disorder characterized by macrothrombocytopenia and absence of ristocetin-induced platelet aggregation. Clinical findings vary from person to person. Most of the patients are diagnosed with muco-cutaneous bleeding such as purpura, epistaxis and gingival bleeding in early childhood. Few pregnant women with BSS are described in the literature. Management of thrombocytopenia during pregnancy and delivery requires a multidisciplinary approach. The family should be warned about the potentially life-threatening bleeding during pregnancy and the delivery and the decision about mode of delivery should be individualised, involving discussion with patient and multidisciplinary team.

Surgery-Associated Bleeding Risk in Patients with Platelet Function Disorders - a Cross Sectional Study with the American Thrombosis and Hemostasis Network Dataset (ATHNdataset)

Introduction: Platelet function disorders (PFDs) are a group of heterogenous bleeding disorders with varying bleeding phenotype. Intraoperative and post-operative bleeding are serious complications among patients with PFDs undergoing surgery. There are very few studies in literature that have specifically investigated surgery associated bleeding complications in PFDs. The aim of this study was to utilize a large national dataset to describe surgeries performed in patients with PFD, characterize the bleeding associated with these surgical procedures and outline the therapeutic approaches adopted. Methods: In this retrospective study, the ATHNdataset was queried for demographic data, PFD diagnosis, surgeries among patients with PFD, intraoperative and post-operative bleeding episodes and treatment. Descriptive statistics were used. The ATHNdataset captures information from patients with bleeding and clotting disorders from over 140 federally funded hemophilia and thrombosis treatment centers (HTCs) in the US. Patients authorize inclusion of their demographic and clinical information in this de-identified Health Insurance Portability and Accountability Act (HIPAA)-compliant data set. Results: From January 2010 to March 2020, the ATHNdataset captured 2767 patients with PFDs, of which 1769 (63.93%) were female and 998 (36.1%) were male, with 1393 patients between 0-18 years (50%) and 1374 (50%) adults >18 years. PFDs identified include 32 patients with Bernard Soulier syndrome (1.16%), 131 patients with Glanzmann thrombasthenia (4.7%), 4 patients with Gray platelet syndrome (0.14%), 29 patients with Hermansky Pudlak syndrome (1%), 1548 patients with storage pool deficiency (55.9%), and 1023 patients diagnosed as PFD (36.9%). A total of 3252 procedures were reported between 2010 and 2020; 1271 patients (46%) patients with at least one documented procedure. Figure 1 shows common procedures among patients with PFDs. Surgery-associated bleeding episodes (includes intraoperative and post-operative bleeds) were reported with 69 procedures (2.1%), which included intraoperative bleeds reported for 18 procedures (0.5%) and post-operative bleeds reported for 51 procedures (1.6%). Of the 60 procedures in patients with Glanzmann thrombasthenia, surgery-associated bleeding episodes were reported after 9 dental procedures (41%), 1 circumcision (25%) and 11 other surgeries/procedures (18.3%). Of the 6 procedures in patients with Bernard Soulier syndrome, no intraoperative or post-operative bleeding episodes were reported. Of 1688 procedures in patients with storage pool deficiency, surgery-associated bleeding episodes were reported after 26 dental procedures (1.5%) and 62 other surgeries/procedures (3.67%). No intraoperative or post-operative mortality was reported among these patients. Of 1272 patients who underwent at least 1 procedure, 646 patients (50.7%) received some form of treatment before/during/after a procedure. Among these 646 patients, 2794 exposure days of hemostasis medications were used before/during/after procedures. Among these, 49% were prior to the procedure, 0.7 % during the procedure and 49.5% after the procedure. Treatments used are shown in figure 2. Conclusion: Our study shows that patients with PFDs have a substantial risk of bleeding associated with surgery. Identifying the risk of bleeding by type and providing appropriate pre-surgical prophylaxis can decrease rates of surgery-associated bleeding in PFDs. Figure 1 Figure 1. Disclosures Sidonio: Sanofi, Takeda, Octapharma, Bayer, Biomain, Grifols, Kedrion, Genentech. Catalyst, Guardian Therapeutics, Novo Nordisk, Hema Biologics, Uniqure.: Consultancy, Honoraria. Ahuja: Genentech: Membership on an entity's Board of Directors or advisory committees; Takeda: Other: DSMB member ; XaTek, Inc: Patents & Royalties; Sanofi: Membership on an entity's Board of Directors or advisory committees.

Dubin Johnson Syndrome associated with defective ristocetin – induced platelet agglutination

Background: This is the first reported case of platelet aggregation defect in association with Dubin-Johnson Syndrome. Case presentation: We reported a 14 months old female infant with recurrent attacks of mild to moderate ear and nose bleeding and moderate amount of subarachnoid hemorrhage with ristocetin induced platelet agglutination other than Von Willebrand Factor disease and Bernard–Soulier syndrome. The patient also had fluctuating bilirubin level (Maximum of 15 mg/dl) and remaining liver function tests were normal; the patient diagnosed as Dubin Johnson Syndrome by liver biopsy. Conclusions: Dubin-Johnson Syndrome may be associated with platelet aggregation defect.

A Novel Mutation in GP1BB Reveals the Role of the Cytoplasmic Domain of GPIbβ in the Pathophysiology of Bernard-Soulier Syndrome and GPIb-IX Complex Assembly

Bernard-Soulier syndrome (BSS) is an autosomal-recessive bleeding disorder caused by biallelic variants in the GP1BA, GP1BB, and GP9 genes encoding the subunits GPIbα, GPIbβ, and GPIX of the GPIb-IX complex. Pathogenic variants usually affect the extracellular or transmembrane domains of the receptor subunits. We investigated a family with BSS caused by the homozygous c.528_550del (p.Arg177Serfs*124) variant in GP1BB, which is the first mutation ever identified that affects the cytoplasmic domain of GPIbβ. The loss of the intracytoplasmic tail of GPIbβ results in a mild form of BSS, characterized by only a moderate reduction of the GPIb-IX complex expression and mild or absent bleeding tendency. The variant induces a decrease of the total platelet expression of GPIbβ; however, all of the mutant subunit expressed in platelets is correctly assembled into the GPIb-IX complex in the plasma membrane, indicating that the cytoplasmic domain of GPIbβ is not involved in assembly and trafficking of the GPIb-IX receptor. Finally, the c.528_550del mutation exerts a dominant effect and causes mild macrothrombocytopenia in heterozygous individuals, as also demonstrated by the investigation of a second unrelated pedigree. The study of this novel GP1BB variant provides new information on pathophysiology of BSS and the assembly mechanisms of the GPIb-IX receptor.

BERNARD SOULIER SYNDROME IN PREGNANCY

Bernard-Soulier syndrome is an inherited platelet disorder, transmitted in an autosomal recessive pattern. Thrombocytopenia and large defective platelets are characteristics, often presents early with bleeding symptoms, such as epistaxis, ecchymosis, menometrorrhagia, and gingival or gastrointestinal bleeding. Diagnosis can be conrmed by platelet aggregation studies and ow cytometry. Differential diagnosis includes other inherited giant platelet disorders, as well as von Willebrand disease and immune thrombocytopenic purpura. During pregnancy, it can present as recurrent rst trimester miscarriages, antepartum, intrapartum and postpartum haemorrhage. Treatment remains generally supportive with platelet transfusions and recombinant factor VII has also been described in literature.

Establishment of a Bernard-Soulier syndrome model in zebrafish

Platelets play an essential role in thrombosis and hemostasis. Abnormal hemostasis can cause spontaneous or severe post-traumatic bleeding. Bernard-Soulier syndrome (BSS) is a rare inherited bleeding disorder caused by a complete quantitative deficiency in the GPIb-IX-V complex. Multiple mutations in GP9 lead to the clinical manifestation of BSS. Understanding the roles and underlying mechanisms of GP9 in thrombopoiesis and establishing a proper animal model of BSS would be valuable to understand the disease pathogenesis and to improve its medical management. Here, by using CRISPR-Cas9 technology, we created a zebrafish gp9SMU15 mutant to model human BSS. Disruption of zebrafish gp9 led to thrombocytopenia and a high bleeding tendency, as well as an abnormal expansion of progenitor cells. The gp9SMU15 zebrafish can be used as a BSS animal model as GP9 roles in thrombocytopoiesis are highly conserved from zebrafish to mammals. Utilizing the BSS model, we verified the clinical GP9 mutations by in vivo functional assay and tested clinical drugs for increasing platelets. Thus, the inherited BSS zebrafish model could be of benefit for in vivo verification of patient-derived GP9 variants of uncertain significance and for potential BSS therapeutic strategy development.

Bernard Soulier syndrome: a rare, frequently misdiagnosed and poorly managed bleeding disorder

Bernard Soulier syndrome is a rare, congenital platelet bleeding disorder, with autosomal recessive inheritance. It is characterised by macrothrombocytopenia and platelet dysfunction, leading to mucocutaneous bleeding noted in early childhood. This entity poses an important diagnostic challenge, and blood smear and DNA sequencing are paramount for the correct diagnosis. Differential diagnosis includes May-Hegglin anomaly, Glanzmann Thrombasthenia and von Willebrand disease; it is also often misdiagnosed as idiopathic thrombocytopenic purpura. We report a 68-year-old man diagnosed with von Willebrand disease for three decades, admitted with gastrointestinal bleeding, anaemia and severe thrombocytopenia. Replacement with von Willebrand factor did not stop the haemorrhage, suggesting another aetiology for the bleeding disorder. Corticosteroids and intravenous immune globulin were also ineffective. Genetic sequencing showed a homozygous mutation in GP1BA gene, thus establishing the correct diagnosis.