Indication for allogeneic stem cell transplantation in Glanzmann’s thrombasthenia

Glanzmann Thrombasthenia: Perspectives from Clinical Practice on Accurate Diagnosis and Optimal Treatment Strategies

Glanzmann thrombasthenia (GT) is a rare autosomal recessive disorder of fibrinogen-mediated platelet aggregation due to a quantitative or qualitative deficit of the α_IIbβ₃ integrin at the platelet surface membrane resulting from mutation(s) in ITGA2B and/or ITGB3. Patients tend to present in early childhood with easy bruising and mucocutaneous bleeding. The diagnostic process requires consideration of more common disorders of haemostasis and coagulation prior to confirming the disorder with platelet light transmission aggregation, flow cytometry of CD41 and CD61 expression, and/or exon sequencing of ITGA2B and ITGB3. Antifibrinolytic therapy, recombinant activated factor VII, and platelet transfusions are the mainstay of therapy, although the latter may trigger formation of anti-platelet antibodies in GT patients and inadvertent platelet-refractory disease. The management of these patients therefore remains complex, particularly in the context of trauma, labour and delivery, and perioperative care. Bone marrow transplantation remains the sole curative option, although the venue of gene therapy is being increasingly explored as a future alternative for definitive treatment of GT.

Successful Use of Hematopoietic Stem Cell Transplantation for 2 Pediatric Cases of Glanzmann Thrombasthenia and Review of the Literature

Glanzmann thrombasthenia is a rare platelet disorder characterized by an abnormal integrin receptor on the surface of platelets that results in the failure of platelets to aggregate. Currently, curative therapy is allogeneic hematopoietic stem cell transplantation (HSCT). The authors report 2 patients with Glanzmann thrombasthenia who successfully underwent allogeneic HSCT from unrelated donors, including one using umbilical cord blood stem cells. Although both patients had evidence of engraftment, hematopoietic recovery, and normalization of platelet aggregation, they also experienced several post-transplant complications. Allogeneic HSCT carries a significant risk of morbidity and mortality that should be considered before proceeding with the transplant.

Anti-αIIb β3 immunization in Glanzmann thrombasthenia: review of literature and treatment recommendations

Glanzmann thrombasthenia (GT) is caused by inherited defects of the α_IIb β₃ 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-α_IIb β₃ 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-α_IIb β₃ antibodies represent one of the most severe complications in GT. Both genetic and environmental factors may contribute to the risk of anti-α_IIb β₃ development, but the underlying pathogenic mechanisms are still unknown. This review will summarize the current knowledge of the risk factors for development of anti-α_IIb β₃ antibodies in patients with GT and discuss how these findings may influence the clinical management of patients.

Genetics of inherited platelet disorders

The current review describes inherited platelet disorders, illustrates their clinical phenotype and molecular genetic defects. Platelets are the key molecules mediating haemostasis via adhesion, activation and clot formation at the site of injury. The inherited platelet disorders can be classified according to their platelet defects: receptor/cytoskeleton defects, secretion disorder, and signal transduction defect.

Patients with inherited thrombocytopathia present with mucous membrane bleedings (epistaxis, gingival bleeding) and may present with serious life threatening bleedings following surgery or trauma. Therefore, biochemical and molecular genetic characterization of inherited platelet disorders is important to understand these disorders and to support an efficient therapy.

Allogeneic hematopoietic cell transplantation in an adult patient with Glanzmann thrombasthenia

Glanzmann thrombasthenia is a rare bleeding disorder that can present life‐threatening bleeding. Our patients develop antiplatelet antibodies that become refractory to any pharmacological treatment. Allogeneic hematopoietic stem‐cell transplantation is the only currently curative procedure, but has major risks mainly in adult; indeed, our patient died.

Megakaryocyte- and megakaryocyte precursor-related gene therapies

Hematopoietic stem cells (HSCs) can be safely collected from the body, genetically modified, and re-infused into a patient with the goal to express the transgene product for an individual's lifetime. Hematologic defects that can be corrected with an allogeneic bone marrow transplant can theoretically also be treated with gene replacement therapy. Because some genetic disorders affect distinct cell lineages, researchers are utilizing HSC gene transfer techniques using lineage-specific endogenous gene promoters to confine transgene expression to individual cell types (eg, ITGA2B for inherited platelet defects). HSCs appear to be an ideal target for platelet gene therapy because they can differentiate into megakaryocytes which are capable of forming several thousand anucleate platelets that circulate within blood vessels to establish hemostasis by repairing vascular injury. Platelets play an essential role in other biological processes (immune response, angiogenesis) as well as diseased states (atherosclerosis, cancer, thrombosis). Thus, recent advances in genetic manipulation of megakaryocytes could lead to new and improved therapies for treating a variety of disorders. In summary, genetic manipulation of megakaryocytes has progressed to the point where clinically relevant strategies are being developed for human trials for genetic disorders affecting platelets. Nevertheless, challenges still need to be overcome to perfect this field; therefore, strategies to increase the safety and benefit of megakaryocyte gene therapy will be discussed.

[Therapy of inherited diseases of platelet function. Interdisciplinary S2K guideline of the Permanent Paediatric Committee of the Society of Thrombosis and Haemostasis Research (GTH e. V.)]

Inherited disorders of platelet function are a heterogeneous group. For optimal prevention and management of bleeding, classification and diagnosis of the underlying defect are highly recommended. An interdisciplinary guideline for a diagnostic approach has been published (AWMF # 086-003 S2K; Hämostaseologie 2014; 34: 201-212). Underlying platelet disorder, platelet count, age and clinical situation modify treatment. Exclusive transfusion of platelet concentrates may be inappropriate as potentially adverse effects can outweigh its benefit. A stepwise and individually adjusted approach for restitution and maintenance of haemostasis is recommended. Administration of antifibrinolytics is generally endorsed, but is of particular use in Quebec disease. Restricted to older children, desmopressin is favourable in storage pool disease and unclassified platelet disorders. Although licensed only for patients with Glanzmann thrombasthenia and alloantibodies, in clinical practice rFVIIa is widely used in inherited platelet disorders with severe bleeding tendency. This guideline aims at presenting the best available advice for the management of patients with inherited platelet function disorders.

Glanzmann thrombasthenia in Pakistan: molecular analysis and identification of novel mutations

Glanzmann thrombasthenia (GT) is an inherited genetic disorder affecting platelets, which is characterized by spontaneous mucocutaneous bleeding and abnormally prolonged bleeding in response to injury or trauma. The underlying defect is failure of platelet aggregation due to qualitative and/or quantitative deficiency of platelet integrin αIIbβ3 resulting from molecular genetic defects in either ITGA2B or ITGB3. Here, we examine a Pakistani cohort of 15 patients with clinical symptoms of GT who underwent laboratory and molecular genetic analysis. In patients with a broad range of disease severity and age of presentation, we identified pathogenic mutations in ITGA2B in 11 patients from 8 different families, including 2 novel homozygous mutations and 1 novel heterozygous mutation. Mutations in ITGB3 were identified in 4 patients from 3 families, two of which were novel homozygous truncating mutations. A molecular genetic diagnosis was established in 11 families with GT, including 5 novel mutations extending the spectrum of mutations in this disease within a region of the world where little is known about the incidence of GT. Mutational analysis is a key component of a complete diagnosis of GT and allows appropriate management and screening of other family members to be performed.

Stem Cell Transplant in Severe Glanzmann Thrombasthenia in an Adult Patient

Glanzmann thrombasthenia is an inherited auto-somal recessive disorder characterized by normal platelet count but lack of platelet aggregation due to absence of platelet glycoprotein IIb/IIIa. The disease usually is associated with mild bleeding, but severe fatal hemorrhage may occur. Allogeneic stem cell transplant is the only curative method of treatment. A literature search showed 18 previously reported cases of Glanzmann thrombasthenia treated with allogeneic hematopoietic stem cell transplant. We report an 18-year-old woman with severe Glanzmann thrombasthenia who was treated with allogeneic hematopoietic stem cell transplant from her sister. After 24-month follow-up, the patient was well, had no bleeding tendency, and had mild chronic skin graft-versus-host disease.

Use of allogeneic stem cell transplantation for moderate-severe Glanzmann thrombasthenia

Glanzmann thrombasthenia (GT) is a rare, autosomal recessive coagulopathy characterized by either qualitative or quantitative abnormalities of the membrane glycoprotein αIIbβ3 complex leading to bleeding tendencies, ranging from purpura to life-threatening hemorrhage. Although patients can be managed with supportive measures including platelet transfusions, complications such as alloimmunization are possible. Allogeneic stem cell transplantation (ASCT) can be indicated in severe cases of GT. We report the case of an eight-month-old girl diagnosed with moderate-severe GT, who was successfully treated with a reduced-intensity, human leukocyte antigen (HLA)-identical ASCT.

High-level transgene expression in induced pluripotent stem cell-derived megakaryocytes: correction of Glanzmann thrombasthenia

Megakaryocyte-specific transgene expression in patient-derived induced pluripotent stem cells (iPSCs) offers a new approach to study and potentially treat disorders affecting megakaryocytes and platelets. By using a Gp1ba promoter, we developed a strategy for achieving a high level of protein expression in human megakaryocytes. The feasibility of this approach was demonstrated in iPSCs derived from two patients with Glanzmann thrombasthenia (GT), an inherited platelet disorder caused by mutations in integrin αIIbβ3. Hemizygous insertion of Gp1ba promoter-driven human αIIb complementary DNA into the AAVS1 locus of iPSCs led to high αIIb messenger RNA and protein expression and correction of surface αIIbβ3 in megakaryocytes. Agonist stimulation of these cells displayed recovery of integrin αIIbβ3 activation. Our findings demonstrate a novel approach to studying human megakaryocyte biology as well as functional correction of the GT defect, offering a potential therapeutic strategy for patients with diseases that affect platelet function.