RESUMO
SLC37A4 encodes an endoplasmic reticulum (ER)-localized multitransmembrane protein required for transporting glucose-6-phosphate (Glc-6P) into the ER. Once transported into the ER, Glc-6P is subsequently hydrolyzed by tissue-specific phosphatases to glucose and inorganic phosphate during times of glucose depletion. Pathogenic variants in SLC37A4 cause an established recessive disorder known as glycogen storage disorder 1b characterized by liver and kidney dysfunction with neutropenia. We report seven individuals who presented with liver dysfunction multifactorial coagulation deficiency and cardiac issues and were heterozygous for the same variant, c.1267C>T (p.Arg423∗), in SLC37A4; the affected individuals were from four unrelated families. Serum samples from affected individuals showed profound accumulation of both high mannose and hybrid type N-glycans, while N-glycans in fibroblasts and undifferentiated iPSC were normal. Due to the liver-specific nature of this disorder, we generated a CRISPR base-edited hepatoma cell line harboring the c.1267C>T (p.Arg423∗) variant. These cells replicated the secreted abnormalities seen in serum N-glycosylation, and a portion of the mutant protein appears to relocate to a distinct, non-Golgi compartment, possibly ER exit sites. These cells also show a gene dosage-dependent alteration in the Golgi morphology and reduced intraluminal pH that may account for the altered glycosylation. In summary, we identify a recurrent mutation in SLC37A4 that causes a dominantly inherited congenital disorder of glycosylation characterized by coagulopathy and liver dysfunction with abnormal serum N-glycans.
Assuntos
Antiporters/genética , Defeitos Congênitos da Glicosilação/etiologia , Retículo Endoplasmático/patologia , Hepatopatias/complicações , Proteínas de Transporte de Monossacarídeos/genética , Mutação , Adulto , Criança , Pré-Escolar , Defeitos Congênitos da Glicosilação/patologia , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Feminino , Fibroblastos/metabolismo , Fibroblastos/patologia , Genes Dominantes , Glicosilação , Humanos , Lactente , Recém-Nascido , Masculino , LinhagemRESUMO
Glanzmann thrombasthenia (GT) is a rare inherited platelet function disorder caused by a quantitative and/or qualitative defect of the αIIbß3 integrin. Pregnancy and delivery are recognized risk periods for bleeding in women with GT. The newborn may also be affected by fetal and neonatal immune thrombocytopenia induced by the transplacental passage of maternal anti-αIIbß3 antibodies, which can lead to severe hemorrhage and fetal loss. Pregnancy in women with GT thus requires a multidisciplinary approach, including prepregnancy counseling and a treatment plan for delivery for both the mother and child. In this article, we summarize the current knowledge on pregnancy in women with GT and describe how we manage this severe platelet disorder in our clinical practice.
Assuntos
Doenças do Recém-Nascido , Púrpura Trombocitopênica Idiopática , Trombastenia , Trombocitopenia Neonatal Aloimune , Feminino , Morte Fetal , Hemorragia , Humanos , Recém-Nascido , Complexo Glicoproteico GPIIb-IIIa de Plaquetas , Gravidez , Trombastenia/terapia , Trombocitopenia Neonatal Aloimune/terapiaRESUMO
BACKGROUND: Centrifugation-based autotransfusion devices only salvage red blood cells while platelets are removed. The same™ device (Smart Autotransfusion for ME; i-SEP, France) is an innovative filtration-based autotransfusion device able to salvage both red blood cells and platelets. The authors tested the hypothesis that this new device could allow a red blood cell recovery exceeding 80% with a posttreatment hematocrit exceeding 40%, and would remove more than 90% of heparin and 75% of free hemoglobin. METHODS: Adults undergoing on-pump elective cardiac surgery were included in a noncomparative multicenter trial. The device was used intraoperatively to treat shed and residual cardiopulmonary bypass blood. The primary outcome was a composite of cell recovery performance, assessed in the device by red blood cell recovery and posttreatment hematocrit, and of biologic safety assessed in the device by the washout of heparin and free hemoglobin expressed as removal ratios. Secondary outcomes included platelet recovery and function and adverse events (clinical and device-related adverse events) up to 30 days after surgery. RESULTS: The study included 50 patients, of whom 18 (35%) underwent isolated coronary artery bypass graft, 26 (52%) valve surgery, and 6 (12%) aortic root surgery. The median red blood cell recovery per cycle was 86.1% (25th percentile to 75th percentile interquartile range, 80.8 to 91.6) with posttreatment hematocrit of 41.8% (39.7 to 44.2). Removal ratios for heparin and free hemoglobin were 98.9% (98.2 to 99.7) and 94.6% (92.7 to 96.6), respectively. No adverse device effect was reported. Median platelet recovery was 52.4% (44.2 to 60.1), with a posttreatment concentration of 116 (93 to 146) · 109/l. Platelet activation state and function, evaluated by flow cytometry, were found to be unaltered by the device. CONCLUSIONS: In this first-in-human study, the same™ device was able to simultaneously recover and wash both platelets and red blood cells. Compared with preclinical evaluations, the device achieved a higher platelet recovery of 52% with minimal platelet activation while maintaining platelet ability to be activated in vitro.
Assuntos
Transfusão de Sangue Autóloga , Procedimentos Cirúrgicos Cardíacos , Adulto , Humanos , Plaquetas , Eritrócitos , Hemoglobinas , HeparinaRESUMO
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.
Assuntos
Trombastenia , Gravidez , Feminino , Humanos , Trombastenia/diagnóstico , Isoanticorpos , Complexo Glicoproteico GPIIb-IIIa de Plaquetas , Plaquetas , Glicoproteínas da Membrana de Plaquetas , EritrócitosRESUMO
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.
Assuntos
Albinismo/sangue , Plaquetas/metabolismo , Síndrome de Hermanski-Pudlak/sangue , Feminino , Humanos , LactenteRESUMO
PURPOSE: Hermansky-Pudlak syndrome (HPS) is characterized by oculocutaneous albinism, excessive bleeding, and often additional symptoms. Variants in ten different genes have been involved in HPS. However, some patients lack variants in these genes. We aimed to identify new genes involved in nonsyndromic or syndromic forms of albinism. METHODS: Two hundred thirty albinism patients lacking a molecular diagnosis of albinism were screened for pathogenic variants in candidate genes with known links to pigmentation or HPS pathophysiology. RESULTS: We identified two unrelated patients with distinct homozygous variants of the BLOC1S5 gene. Patients had mild oculocutaneous albinism, moderate bleeding diathesis, platelet aggregation deficit, and a dramatically decreased number of platelet dense granules, all signs compatible with HPS. Functional tests performed on platelets of one patient displayed an absence of the obligate multisubunit complex BLOC-1, showing that the variant disrupts BLOC1S5 function and impairs BLOC-1 assembly. Expression of the patient-derived BLOC1S5 deletion in nonpigmented murine Bloc1s5-/- melan-mu melanocytes failed to rescue pigmentation, the assembly of a functional BLOC-1 complex, and melanosome cargo trafficking, unlike the wild-type allele. CONCLUSION: Mutation of BLOC1S5 is disease-causing, and we propose that BLOC1S5 is the gene for a new form of Hermansky-Pudlak syndrome, HPS-11.
Assuntos
Síndrome de Hermanski-Pudlak , Alelos , Animais , Plaquetas , Síndrome de Hermanski-Pudlak/genética , Humanos , Camundongos , MutaçãoRESUMO
Glanzmann thrombasthenia (GT) is caused by inherited defects of the αIIb ß3 platelet glycoprotein. This bleeding disorder can be treated with platelet transfusion therapy, but some patients will be immunized and begin to form anti-human leucocyte antigen (HLA) and/or anti-αIIb ß3 antibodies. These antibodies can bind and interfere with the function of the transfused platelets, rendering treatment ineffective. However, platelet transfusion refractoriness attributable to HLA antibodies may be managed by the selection of compatible donors, although they are not always readily available, particularly in an emergency. Thus, anti-αIIb ß3 antibodies represent one of the most severe complications in GT. Both genetic and environmental factors may contribute to the risk of anti-αIIb ß3 development, but the underlying pathogenic mechanisms are still unknown. This review will summarize the current knowledge of the risk factors for development of anti-αIIb ß3 antibodies in patients with GT and discuss how these findings may influence the clinical management of patients.
Assuntos
Autoanticorpos , Imunização , Complexo Glicoproteico GPIIb-IIIa de Plaquetas , Transfusão de Plaquetas/efeitos adversos , Trombastenia , Reação Transfusional , Autoanticorpos/sangue , Autoanticorpos/imunologia , Humanos , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/imunologia , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/metabolismo , Fatores de Risco , Trombastenia/sangue , Trombastenia/imunologia , Trombastenia/terapiaRESUMO
Platelet δ-storage pool disease (δ-SPD) is a platelet function disorder characterized by a reduction in the number or content of dense granules. Reports on δ-SPD are mostly limited to case presentations. We aimed to retrospectively describe a series of patients with δ-SPD to better characterize the disease. We studied 16 patients with congenital or acquired δ-SPD. Lumiaggregometry, α- and δ-granules content, platelet ultrastructure, αIIbß3 integrin, and glycoprotein Ib (GPIb) activation were assessed. Most of the patients generally demonstrate mild to moderate bleeding diathesis. Platelet aggregation studies showed moderate abnormalities with variable profiles, while all the individuals had almost complete absence of adenosine triphosphate release. Mepacrine capture, CD63 expression, and study of dense granules by electron microscopy enabled to distinguish different subtypes of δ-SPD with quantitative or qualitative defect. Surprisingly, significantly decreased GPIb expression levels after platelet activation with thrombin receptor activating peptide 50 µM were found, suggesting that GPIb-impaired mobilization may represent an additional feature of the disorder. In conclusion, δ-SPD represents a complex disorder with various clinical and biological aspects, requiring a great deal of expertise to be properly diagnosed.
Assuntos
Plaquetas/metabolismo , Microscopia Eletrônica/métodos , Deficiência do Pool Plaquetário , Feminino , Humanos , Masculino , Agregação PlaquetáriaRESUMO
Variants in ETV6, which encodes a transcription repressor of the E26 transformation-specific family, have recently been reported to be responsible for inherited thrombocytopenia and hematologic malignancy. We sequenced the DNA from cases with unexplained dominant thrombocytopenia and identified six likely pathogenic variants in ETV6, of which five are novel. We observed low repressive activity of all tested ETV6 variants, and variants located in the E26 transformation-specific binding domain (encoding p.A377T, p.Y401N) led to reduced binding to corepressors. We also observed a large expansion of megakaryocyte colony-forming units derived from variant carriers and reduced proplatelet formation with abnormal cytoskeletal organization. The defect in proplatelet formation was also observed in control CD34+ cell-derived megakaryocytes transduced with lentiviral particles encoding mutant ETV6. Reduced expression levels of key regulators of the actin cytoskeleton CDC42 and RHOA were measured. Moreover, changes in the actin structures are typically accompanied by a rounder platelet shape with a highly heterogeneous size, decreased platelet arachidonic response, and spreading and retarded clot retraction in ETV6 deficient platelets. Elevated numbers of circulating CD34+ cells were found in p.P214L and p.Y401N carriers, and two patients from different families suffered from refractory anemia with excess blasts, while one patient from a third family was successfully treated for acute myeloid leukemia. Overall, our study provides novel insights into the role of ETV6 as a driver of cytoskeletal regulatory gene expression during platelet production, and the impact of variants resulting in platelets with altered size, shape and function and potentially also in changes in circulating progenitor levels.
Assuntos
Plaquetas/metabolismo , Mutação em Linhagem Germinativa , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Proteínas Proto-Oncogênicas c-ets/genética , Proteínas Repressoras/genética , Trombopoese/genética , Antígenos CD34/metabolismo , Contagem de Células Sanguíneas , Diferenciação Celular , Família , Feminino , Regulação da Expressão Gênica , Genótipo , Humanos , Hiperplasia , Masculino , Megacariócitos/citologia , Megacariócitos/metabolismo , Megacariócitos/patologia , Linhagem , Fenótipo , Contagem de Plaquetas , Proteínas Proto-Oncogênicas c-ets/metabolismo , Proteínas Repressoras/metabolismo , Transcrição Gênica , Variante 6 da Proteína do Fator de Translocação ETSRESUMO
Inherited thrombocytopenia (IT) is a heterogeneous group of rare diseases that are often confused with immune thrombocytopenia (ITP). The objective of this study was to supply clinicobiological elements that allow a distinction to be drawn between IT and chronic ITP. We then compared 23 adult patients with IT and 9 patients with chronic ITP. Our study revealed six discriminating criteria: (i) an age of discovery <34 years: positive predictive value (PPV) = 88.2% [63.6; 98.5], (ii) a family history of thrombocytopenia: PPV = 100.0% [82.4; 100.0], (iii) a personal history of bleeding: PPV = 100% [76.8; 100.0], (iv) a mean platelet volume >11 fL: PPV = 93.3% [68.1; 99.8], (v) an excess of giant platelets on blood smear: 100.0% [76.8; 100.0], and (vi) a percentage >44% of platelets with a surface area >4 µm(2) in electron microscopy: PPV = 83.3% [58.6; 96.4]. If at least three of these criteria were combined, it was possible to distinguish IT from chronic ITP with 91.3% [72.0; 98.9] sensitivity and PPV = 100.0% [66.4; 100.0] specificity. The secondary objective of this study was to assess the prevalence of potential IT diagnosis in patients with chronic thrombocytopenia of uncertain origin. Applying our diagnostic approach to a series of 20 cases allowed us to estimate that 40% of them could be suffering from IT. Finally, our diagnostic approach may help to correctly distinguish IT from chronic ITP, particularly in the context of macrothrombocytopenia.
Assuntos
Púrpura Trombocitopênica Idiopática/diagnóstico , Trombocitopenia/diagnóstico , Trombocitopenia/etiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Autoanticorpos/imunologia , Plaquetas/imunologia , Plaquetas/metabolismo , Plaquetas/ultraestrutura , Comorbidade , Diagnóstico Diferencial , Feminino , Seguimentos , Testes Genéticos , Hemorragia/etiologia , Humanos , Masculino , Volume Plaquetário Médio , Pessoa de Meia-Idade , Mutação , Contagem de Plaquetas , Testes de Função Plaquetária , Púrpura Trombocitopênica Idiopática/sangue , Púrpura Trombocitopênica Idiopática/complicações , Púrpura Trombocitopênica Idiopática/imunologia , Sensibilidade e Especificidade , Trombocitopenia/sangue , Trombocitopenia/complicações , Adulto JovemRESUMO
We report the largest international study on Glanzmann thrombasthenia (GT), an inherited bleeding disorder where defects of the ITGA2B and ITGB3 genes cause quantitative or qualitative defects of the αIIbß3 integrin, a key mediator of platelet aggregation. Sequencing of the coding regions and splice sites of both genes in members of 76 affected families identified 78 genetic variants (55 novel) suspected to cause GT. Four large deletions or duplications were found by quantitative real-time PCR. Families with mutations in either gene were indistinguishable in terms of bleeding severity that varied even among siblings. Families were grouped into type I and the rarer type II or variant forms with residual αIIbß3 expression. Variant forms helped identify genes encoding proteins mediating integrin activation. Splicing defects and stop codons were common for both ITGA2B and ITGB3 and essentially led to a reduced or absent αIIbß3 expression; included was a heterozygous c.1440-13_c.1440-1del in intron 14 of ITGA2B causing exon skipping in seven unrelated families. Molecular modeling revealed how many missense mutations induced subtle changes in αIIb and ß3 domain structure across both subunits, thereby interfering with integrin maturation and/or function. Our study extends knowledge of GT and the pathophysiology of an integrin.
Assuntos
Mutação , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/genética , Trombastenia/genética , Estudos de Coortes , Análise Mutacional de DNA , Éxons , Rearranjo Gênico , Estudos de Associação Genética , Testes Genéticos , Genótipo , Humanos , Integrina alfa2/química , Integrina alfa2/genética , Integrina beta3/química , Integrina beta3/genética , Modelos Moleculares , Fenótipo , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/química , Conformação Proteica , Domínios e Motivos de Interação entre Proteínas , Sítios de Splice de RNA , Splicing de RNA , Deleção de Sequência , Trombastenia/diagnósticoAssuntos
Síndrome de Bernard-Soulier/genética , Complexo Glicoproteico GPIb-IX de Plaquetas/genética , Adolescente , Adulto , Síndrome de Bernard-Soulier/epidemiologia , Criança , Pré-Escolar , Feminino , França/epidemiologia , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Mutação , Prevalência , Reunião , Adulto JovemAssuntos
Antígenos de Plaquetas Humanas/imunologia , Peptídeos e Proteínas de Sinalização Intercelular/genética , Isoanticorpos/imunologia , Complicações Hematológicas na Gravidez/etiologia , Complicações Hematológicas na Gravidez/terapia , Trombocitopenia/etiologia , Trombocitopenia/terapia , Regiões 5' não Traduzidas , Adulto , Biomarcadores , Coagulação Sanguínea , Testes de Coagulação Sanguínea , Gerenciamento Clínico , Suscetibilidade a Doenças , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Mutação em Linhagem Germinativa , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Gravidez , Complicações Hematológicas na Gravidez/diagnóstico , Trombocitopenia/diagnósticoAssuntos
Antibacterianos/efeitos adversos , Autoanticorpos/imunologia , Doenças Autoimunes/terapia , Ceftriaxona/efeitos adversos , Deficiência do Fator V/terapia , Fator V/imunologia , Transfusão de Plaquetas , Cuidados Pré-Operatórios/métodos , Substituição da Valva Aórtica Transcateter , Idoso de 80 Anos ou mais , Antibacterianos/uso terapêutico , Anticoagulantes/uso terapêutico , Estenose da Valva Aórtica/complicações , Estenose da Valva Aórtica/cirurgia , Fibrilação Atrial/complicações , Fibrilação Atrial/tratamento farmacológico , Autoanticorpos/sangue , Doenças Autoimunes/diagnóstico , Doenças Autoimunes/imunologia , Ceftriaxona/uso terapêutico , Terapia Combinada , Emergências , Deficiência do Fator V/diagnóstico , Deficiência do Fator V/imunologia , Feminino , Insuficiência Cardíaca/etiologia , Humanos , Tempo de Tromboplastina Parcial , Prednisona/uso terapêutico , Tempo de Protrombina , Pirazóis/efeitos adversos , Pirazóis/uso terapêutico , Piridonas/efeitos adversos , Piridonas/uso terapêutico , Infecções Urinárias/complicações , Infecções Urinárias/tratamento farmacológicoRESUMO
Prasugrel is a widely used antiplatelet agent in the setting of percutaneous coronary intervention. In case of resistance to this third-generation thienopyridine, choices of alternative drugs remain limited. Here, we describe a case of a 49-year-old man with stent thrombosis occurring 5 days after drug-eluting stent implantation despite a well-conducted antiplatelet therapy with aspirin and prasugrel. Evaluation of platelet functions by different tests revealed prasugrel resistance. Genotyping for various CYP single-nucleotide polymorphisms showed that the patient carried mutant alleles encoding enzymes CYP2B6 and CYP2C9 involved in prasugrel metabolic pathway. Strikingly, an adequate platelet response was rapidly obtained after switching from prasugrel to ticagrelor.
Assuntos
Adenosina/análogos & derivados , Piperazinas/efeitos adversos , Antagonistas do Receptor Purinérgico P2Y/uso terapêutico , Tiofenos/efeitos adversos , Trombose/tratamento farmacológico , Adenosina/uso terapêutico , Resistência a Medicamentos , Humanos , Masculino , Pessoa de Meia-Idade , Cloridrato de Prasugrel , Trombose/etiologia , TicagrelorRESUMO
BACKGROUND: Glanzmann thrombasthenia (GT) is caused by an inherited defect of platelet αIIbß3 integrin. Concizumab, a monoclonal antibody specific for tissue factor pathway inhibitor, abolishes its anticoagulant effect. OBJECTIVES: To evaluate the in vitro ability of concizumab to improve hemostasis in GT. METHODS: The effects of concizumab were evaluated in whole blood or platelet-rich plasma from GT patients (n = 5-9) using a thrombin generation assay, rotational thromboelastometry (ROTEM), a global fibrinolytic capacity assay, and a flow chamber assay (Total Thrombus formation Analysis System). Washed platelets (WPs) and 20 nM recombinant activated factor VII (rFVIIa) were included for comparison. RESULTS: The lag time in the thrombin generation assay was significantly longer (+85%; P < .0001) in GT patients than in controls. WPs, rFVIIa, and concizumab each significantly improved thrombin generation profiles. The ROTEM clotting time (CT) was significantly longer in GT patients than in controls (677 seconds vs 523 seconds; P = .03). However, CT improved after adding WPs, rFVIIa, or concizumab. Under flow, occlusive thrombi were present in all healthy controls after 10 minutes, whereas platelet-fibrin depositions were not seen in GT patients. Subocclusive or occlusive thrombi formed when GT blood was mixed with WPs, rFVIIa, or concizumab. Clots in GT platelet-rich plasma were more susceptible to fibrinolysis and were improved by WPs, rFVIIa, or concizumab. CONCLUSION: Concizumab enhanced thrombin generation, decreased the ROTEM CT, improved thrombus formation under flow, and reduced clot lysis. Our results demonstrate the potential of concizumab for subcutaneous prophylaxis in GT patients.
Assuntos
Anticorpos Monoclonais Humanizados , Fator VIIa , Hemostasia , Trombastenia , Tromboelastografia , Humanos , Trombastenia/sangue , Trombastenia/tratamento farmacológico , Hemostasia/efeitos dos fármacos , Anticorpos Monoclonais Humanizados/uso terapêutico , Anticorpos Monoclonais Humanizados/farmacologia , Adulto , Masculino , Feminino , Trombina/metabolismo , Coagulação Sanguínea/efeitos dos fármacos , Plaquetas/efeitos dos fármacos , Plaquetas/metabolismo , Proteínas Recombinantes , Fibrinólise/efeitos dos fármacos , Pessoa de Meia-Idade , Adulto Jovem , Adolescente , Trombose/sangue , Trombose/prevenção & controle , Trombose/tratamento farmacológico , Estudos de Casos e Controles , LipoproteínasRESUMO
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.
RESUMO
Background: In hemophilia and von Willebrand disease, the degree of alteration of laboratory assays correlates with bleeding manifestations. Few studies have assessed the predictive value for bleeding of laboratory assays in patients with inherited platelet function disorders (IPFDs). Objectives: To assess whether there is an association between platelet function assay results and bleeding history, as evaluated by the International Society on Thrombosis and Haemostasis (ISTH) bleeding assessment tool (BAT). Methods: Centers participating in the international ISTH-BAT validation study were asked to provide results of the diagnostic assays employed for the patients they enrolled, and the association with the individual patients' bleeding score (BS) was assessed. Results: Sixty-eight patients with 14 different IPFDs were included. Maximal amplitude of platelet aggregation was significantly lower in patients with a pathologic BS and correlated inversely with the BS, a finding largely driven by the subgroup of patients with Glanzmann thrombasthenia and CalDAG-GEFI deficiency; after their exclusion, TRAP-induced aggregation remained significantly lower in patients with a pathologic BS. Bleeding time was significantly more prolonged in patients with a high BS than in those with a normal BS (27.1 ± 6.2 minutes vs 15.1 ± 10.6 minutes; P < .01). Reduced α-granule content was significantly more common among patients with a pathologic BS than among those with a normal BS (80% vs 20%; P < .05). Receiver operating characteristic curve analysis revealed a significant discriminative ability of all the aforementioned tests for pathologic BS (P < .001), also after exclusion of patients with Glanzmann thrombasthenia and CalDAG-GEFI deficiency. Conclusion: This study shows that altered platelet laboratory assay results are associated with an abnormal ISTH-BAT BS in IPFD.