Acquired Glanzmann Thrombasthenia in a Pediatric Patient with Alagille Syndrome

Introduction/Objective Acquired Glanzmann Thrombasthenia is a rare bleeding disorder that is characterized by inhibition of glycoprotein IIb/IIIa signaling, usually by an autoantibody, leading to an interference in platelet aggregation. Clinically, this disorder presents with spontaneous mucocutaneous bleeding in the setting of a normal platelet count. Acquired Glanzmann Thrombasthenia has been associated with primary immune thrombocytopenic purpura (ITP), several types of hematologic and solid malignancies, solid organ transplants, and other autoimmune disorders. Methods/Case Report A 4-year-old female patient with a history of Alagille Syndrome requiring liver transplant at age 3 was admitted to the hospital after presenting to the emergency department with complaints of bruising, nosebleeds, and a petechial rash. The patient was found to have a platelet count of 11 K/mm3 and was diagnosed with ITP. The patient received a single dose of IVIG at 1g/kg with subsequent resolution of bleeding and a recovering platelet count of 27 K/mm3 12 hours after administration. However, two months later, the patient presented again with worsening bruising, multiple nosebleeds per day, and worsening petechiae. Lab studies revealed the patient’s platelet count was within normal limits. A platelet antibody screen was positive with a subsequent Platelet Antibody Bead Array revealing anti-Gp IIb/IIIa HPA-1 and HPA-3 positivity. Results (if a Case Study enter NA) N/A Conclusion Acquired Glanzmann Thrombasthenia is a rare bleeding disorder that is the result of interference with platelet aggregation. Antibodies that may be associated with any of several underlying conditions lead to impaired platelet function and subsequent mucocutaneous bleeding. The present case represents an occurrence of Acquired Glanzmann Thrombasthenia in a patient with multiple risk factors for development of the disorder.

How I Manage cyclic thrombocytopenia

Cyclic thrombocytopenia (CTP) is a rare disease, which is characterized by periodic fluctuation of the platelet count. The pathogenesis of CTP is unknown and most likely heterogeneous. Patients with CTP are almost always misdiagnosed as having primary immune thrombocytopenia (ITP). The interval between ITP and CTP diagnosis can be many years. CTP patients often receive ITP-specific therapies including corticosteroids, thrombopoietin receptor agonists, rituximab and splenectomy which are followed by a transient increase in platelet count that is wrongly attributed to treatment effect with inevitable "relapse". CTP can be diagnosed by frequent platelet count monitoring which reveals a typical pattern of periodic platelet cycling. An early diagnosis of CTP will prevent these patients from being exposed to possibly harmful therapies. The bleeding phenotype is usually mild and consists of mucocutaneous bleeding at the time when the platelet count is at its nadir. Severe bleeding from other sites can occur but is rare. Some patients respond to cyclosporine A or to danazol, but most patients do not respond to any therapy. CTP can be associated with hematological malignancies or disorders of the thyroid gland. Nevertheless, spontaneous remissions can occur, even after many years.

Defective Platelet Thromboxane A2 Signaling and Serotonin Release in the Pathogenesis of Bleeding during Viral Infection

Viral hemorrhagic fever (VHF) refers to a group of diverse acute human diseases caused by single stranded RNA viruses typically associated with fever, vascular damage and abnormal vascular barrier function. These infections are a continuing threat to public health due to the high case-fatality rate and potential bioterrorism threats. Critically infected VHF patients with unfavorable prognosis often present bleeding symptoms and shock. Thrombocytopenia associated with endothelial, coagulation and platelet dysfunction has been reported during these infections, but their relationship to bleeding is still poorly defined. We have previously established that infection by lymphocytic choriomeningitis virus (LCMV) in extremely thrombocytopenic mice causes severe mucocutaneous bleeding and death mediated by interferon α/β receptor (IFNAR) signaling. We now show in vivo that IFNAR is expressed on megakaryocytes but not on circulating platelets, contrary to previously reported evidence. To explain how increased IFN-I in LCMV-infected mice alters the function of platelets lacking IFNAR, we cross-transplanted WT or IFNAR-/- bone marrow (BM) cells into IFNAR-/- and WT mice. Upon platelet depletion and LCMV infection, only chimeras with WT bone marrow died, suggest that IFN-I-sensitive bone marrow-derived cells are responsible for the mucocutaneous bleeding observed in conditions of extreme thrombocytopenia. Moreover, the results of BM transplantation studies prove that endothelial cell alterations and infection-related inflammatory conditions are not alone sufficient to cause hemorrhage. Circulating platelets during LCMV infection show a generalized aggregation disfunction that persists longer for the arachidonic acid/thromboxane A2 (AA/TBXA2) activation pathway. These aggregation defects are associated, and possibly linked to an impaired secretory ability of both α- and δ-granule. Since circulating platelets are unresponsive to IFN-I, these findings are consistent with the possibility that bone marrow-resident megakaryocytes are targets of IFN-I stimulation during LCMV infection and are the origin of structural and functional platelet abnormalities observed in the circulation. Indeed, megakaryocytes from LCMV-infected mice exhibited fewer granules limited to the perinuclear zone rather than normally diffused throughout the demarcation membrane system; the latter was also underdeveloped. Moreover, platelet transcriptome evaluation of genes involved in platelet production and function showed that IFN-I downregulates bone marrow expression of NF-E2 - a key transcription factor for thrombocytopoiesis - as well as of cyclooxygenase-1 and thromboxane-A synthase. The latter enzymes are required for TBXA2 synthesis from AA amplifying platelet activation. Thus, in addition to being decreased in number, circulating platelets of LCMV-infected animals have impaired activation-induced cargo release from storage granules supporting hemostasis. Experimentally, we observed that bleeding during LCMV infection is increased following aspirin, but not clopidogrel, administration. This suggested that serotonin secretion may be the final effector required to control erythrocyte extravasation. Accordingly, bleeding associated with LCMV infection was markedly enhanced in mice lacking platelet serotonin (TPH1-/-mice), and this was ameliorated by transfusion of normal platelets. In conclusion, we have identified a IFN-I targeting of megakaryocytes leading to reduced production of dysfunctional platelets with abnormal serotonin release as the cause of potentially lethal bleeding in a mouse model of arenavirus infection. Our demonstration that infusion of viable platelets can prevent lethal anemia in LCMV-infected susceptible mouse strains indicates that the same therapeutic intervention monitored by platelet response to AA stimulation may aid in treating severe VHF cases in human patients. Disclosures Aiolfi: MERU-VasImmune, Inc: Other: Stock option. Ruggeri:MERU-VasImmune Inc.: Equity Ownership, Other: CEO and Founder.

A Case of Bernard-Soulier Syndrome due to a Novel Homozygous Missense Mutation in an Exon of the GP1BA Gene

Bernard-Soulier syndrome (BSS) is an extremely rare autosomal recessive bleeding disorder clinically characterized by macrothrombocytopenia and a mucocutaneous bleeding tendency. A 1-year-old Chinese patient who was born to consanguineous parents was diagnosed with early onset of BSS. Gene sequencing and bioinformatics analysis were conducted. We identified a novel homozygous missense mutation (c.790T>C) in the GP1BAgene that causes an amino acid residue substitution of a cysteine with an arginine that might have a deleterious effect on the protein function as predicted by bioinformatics analysis. If a patient has clinical manifestations that include recurrent mucocutaneous bleeding, a mean platelet volume and platelet-large cell ratio above normal levels, and giant platelets on a peripheral smear and has consanguineous parents, a diagnosis of BSS can be suspected. In these situations, gene sequencing for mutations in the GPIb-IX-V complex is necessary.

Risk Factors and Manageability of the Mainly Mild Mucocutaneous Bleeding Profile Observed in Attp Patients Treated with Caplacizumab during the Phase III Hercules Study

Introduction : Acquired thrombotic thrombocytopenic purpura (aTTP) is a rare, life-threatening autoimmune blood clotting disorder, manifested by systemic microvascular thrombosis leading to profound thrombocytopenia, hemolytic anemia, and organ ischemia. Results of the Phase 3 HERCULES study demonstrated the efficacy of caplacizumab in aTTP patients (Scully et al., Blood 2017;130:LBA-1). Consistent with its mechanism of action, an increase in mainly mild mucocutaneous bleeding events was observed in patients treated with caplacizumab. Here we report on the risk factors and manageability of these bleeding events. Methods : Analyses were performed on the study's safety population (i.e., all patients who received at least 1 administration of study drug). Bleeding-related treatment-emergent adverse events (TEAEs) were identified using the Standardized MedDRA (Medical Dictionary for Regulatory Activities) Query (SMQ) for 'Hemorrhage', excluding laboratory terms and the Preferred Term TTP. Bleeding events were analyzed in relation to the use of concomitant antithrombotic therapy and direct oral anticoagulants (DOACs), the severity of the bleeding events, and the requirement and type of therapeutic intervention. Bleeding-related TEAEs were analyzed during the double-blind treatment period. Results : The safety population consisted of 71 caplacizumab- and 73 placebo-treated patients. During the treatment period, at least one bleeding event was reported in 44 patients (62.0%; in total 108 events) in the caplacizumab group and 34 patients (46.6%; in total 61 events) in the placebo group. Twelve patients (16.9%) had a bleeding event while on concomitant antithrombotic therapy in the caplacizumab group vs. 9 patients (12.3%) in the placebo group. In patients not receiving antithrombotics, or in patients in whom the bleeding event occurred prior to onset of antithrombotic therapy, bleeding event occurred in 32 patients (45.1%) in the caplacizumab group vs. 26 patients in the placebo group (35.6%). Table 1 summarizes the most frequent bleeding events in relation to the use of antithrombotic therapy. Of note, 3 patients (4.2%) in the caplacizumab group vs. none in the placebo group received a DOAC while on study drug treatment (all administered for the treatment of major thromboembolic events). All 3 patients were reported with at least 1 bleeding event. One of these events was a SAE of menorrhagia which was treated with transfusion of red blood cells and resolved. Other events were mild AEs of epistaxis, injection site hemorrhage and gingival bleeding (all resolved without therapy). The majority of bleeding TEAEs were of mild or moderate severity (Table 2). The most common mild or moderate bleeding events in the caplacizumab group were epistaxis (27 mild events in 17 patients [23.9%] and 6 moderate events in 5 patients [7.0%]), gingival bleeding (12 mild events in 11 patients [15.5%]) and contusion (6 mild events in 5 patients [7.0%], and 1 patient [1.4%] with a moderate event). In the placebo group, contusion was the most frequently reported bleeding event (22 mild events in 9 patients [12.3%] and 2 moderate events in 1 patient [1.4%]). Severe bleeding TEAEs were epistaxis (treated with Wilate), gingival bleeding (treated with tranexamic acid), and upper gastrointestinal hemorrhage (requiring transfusion of red blood cells) each in 1 patient (1.4%) in the caplacizumab group. In the placebo group there was 1 severe (fatal) bleeding of hemorrhagic transformation stroke. Overall, therapeutic intervention for bleeding events was reported in 14 patients (19.7%) in the caplacizumab group for a total of 15 events (15/108 [13.9%]), compared to 2 patients (2.7%) in the placebo group for a total of 2 events (2/61 [3.3%]). Conclusions : The safety profile of caplacizumab was favorable. In line with its pharmacology, treatment with caplacizumab was associated with an increased risk of mucocutaneous bleeding. These events were generally mild to moderate, and the majority did not require therapeutic intervention. While the number of patients receiving DOACs was low, no increased risk for bleeding with antithrombotic therapy was observed. Disclosures Cataland: Alexion: Research Funding; Shire: Consultancy; Ablynx: Consultancy, Other: Member of Advisory Board. Scully:Novartis: Honoraria, Other: Member of Advisory Board, Speakers Bureau. Peyvandi:Novo Nordisk: Speakers Bureau; Shire: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Shire: Speakers Bureau; Roche: Speakers Bureau; Roche: Speakers Bureau; Kedrion: Consultancy; Grifols: Speakers Bureau; Novo Nordisk: Speakers Bureau; Novo Nordisk: Speakers Bureau; Sobi: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Shire: Speakers Bureau; Grifols: Speakers Bureau; Kedrion: Consultancy; Octapharma US: Honoraria; Novo Nordisk: Speakers Bureau; Grifols: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Roche: Speakers Bureau; Shire: Speakers Bureau; Grifols: Speakers Bureau; Kedrion: Consultancy; Sobi: Speakers Bureau; Grifols: Speakers Bureau; Novo Nordisk: Speakers Bureau; Kedrion: Consultancy; Sobi: Speakers Bureau; Octapharma US: Honoraria; Roche: Speakers Bureau; Roche: Speakers Bureau; Octapharma US: Honoraria; Sobi: Speakers Bureau; Sobi: Speakers Bureau; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Kedrion: Consultancy; Octapharma US: Honoraria; Octapharma US: Honoraria; Ablynx: Other: Member of Advisory Board, Speakers Bureau; Shire: Speakers Bureau. Coppo:Ablynx: Consultancy. Knöbl:Ablynx: Consultancy, Other: Member of Advisory Board. Kremer Hovinga:Shire: Other: Member of Advisory Board, Research Funding; Ablynx: Other: Member of Advisory Board. Metjian:Ablynx: Other: Member of Advisory Board. De La Rubia:Ablynx: Consultancy, Other: Member of Advisory Board. Minkue:Ablynx: Employment. Sousa:Ablynx: Employment. Callewaert:Ablynx: Employment. De Winter:Ablynx: Employment.