T suppressor activated lymphocytes (CD8+/DR+) inhibit megakaryocyte progenitor cell differentiation in a case of acquired amegakaryocytic thrombocytopenic purpura

Case Report: Successful Avatrombopag Treatment for Two Cases of Anti-PD-1 Antibody-Induced Acquired Amegakaryocytic Thrombocytopenia

Background: Anti-PD-1/PD-L1 immunotherapy has achieved impressive responses in multiple types of malignancies in recent years. However, immune-related adverse events (irAEs) occur and limit their continuous clinical use. Among these irAEs, acquired amegakaryocytic thrombocytopenia (AAT) is rare but often clinically serious, life-threatening and refractory to multiple treatment approaches.

Case summary: We reported for the first time the successful treatment of avatrombopag in two cases of anti-PD1 antibody-induced AAT (in particular, one case had progressed to aplastic anemia), which was refractory or intolerant to glucocorticoids, ciclosporin, intravenous immunoglobulin (IVIG), recombinant human thrombopoietin (rh-TPO) and even TPO receptor agonist (TPO-RA) eltrombopag. To date, the two cases manifested as normal platelet counts and are independent of transfusion.

Conclusion: Anti-PD1 antibody-induced AAT occurs with low frequency but is often serious and difficult to manage, for which this study proposed vatrombopag as a potential curative and safe approach.

Acquired amegakaryocytic thrombocytopenia after durvalumab administration

Immune checkpoint inhibitors (ICIs), despite their ability to potentiate antitumor T-cell responses, may cause various immune-related adverse events. Most cases of thrombocytopenia induced by ICIs have revealed a pathophysiologic mechanism of immune thrombocytopenia with increased platelet destruction and preserved megakaryocytes. Acquired amegakaryocytic thrombocytopenic purpura (AATP) is an unusual disorder characterized by thrombocytopenia with markedly diminished bone marrow megakaryocytes in the presence of otherwise normal hematopoiesis. AATP caused by ICIs has not been reported on. Herein, we present the case of a 79-year-old man diagnosed with squamous cell carcinoma of the lung who developed AATP after two courses of durvalumab, a drug targeting programmed death-ligand 1. Two weeks after the second cycle, his platelet count decreased to 2.1 × 10⁴/μL. After the patient underwent platelet transfusion, his platelet count increased to 8.1 × 10⁴/μL the next day but subsequently decreased repeatedly even after the ICI was discontinued. Six weeks after the second cycle, he developed interstitial pneumonia and was administered prednisolone (50 mg/day). However, thrombocytopenia did not improve. Bone marrow biopsy showed scarce megakaryocytes (< 1 megakaryocyte/10 high-power fields) with preservation of myeloid and erythroid series. Myelodysplasia, myelofibrosis, or metastatic lesions were not observed. Cytogenetic analysis showed a normal male karyotype of 46XY. Hence, the patient received eltrombopag, a thrombopoietin receptor agonist, and his platelet count subsequently improved. After recovery, bone marrow aspiration revealed a normal number of megakaryocytes. AATP is rarely the type of thrombocytopenia induced by ICIs and may be successfully treated with thrombopoietin receptor agonists.

Pure red cell aplasia and amegakaryocytic thrombocytopenia in thymoma: The uncharted territory

Association between thymoma and pure red cell aplasia is already well-documented in literature whereas acquired amegakaryocytic thrombocytopenia is rarely reported. In this case, even with the addition of eltrombopag to standard immunosuppression, the cytopenias did not improve, probably due to the lack of surgical resection of the tumor.

Acquired Amegakaryocytic Thrombocytopenia in Adult-onset Still's Disease: Successful Combination Therapy with Tocilizumab and Cyclosporine

Adult-onset Still's disease (AOSD) sometimes demonstrates hematologic disorder, whereas acquired amegakaryocytic thrombocytopenia (AAT) involvement is extremely rare. We herein report a 67-year-old woman with relapse of AOSD who concomitantly developed AAT. Thrombocytopenia along with high disease activity of AOSD was resistant to high-dose prednisolone, even in combination with methotrexate and tacrolimus. However, alternative treatment with cyclosporine after administering tocilizumab resulted in the improvement of thrombocytopenia, ultimately demonstrating that combination therapy based on suppressing the intractable disease activity of AOSD and subsequently adding a reliable immunosuppressant was required to achieve remission.

Participation of B-cell-activating factor receptors in the pathogenesis of immune thrombocytopenia

ESSENTIALS: Dysfunctional B-cell-activating factor (BAFF) system is related to many autoimmune diseases. The regulatory functions of BAFF/BAFF receptors were investigated in an in vitro coculture system. Different regulatory roles of BAFF were investigated via different receptors in immune thrombocytopenia. The upregulated BAFF receptors on autoreactive lymphocytes lead to their hypersensitivity to BAFF.

SUMMARY

BACKGROUND

The pathogenesis of immune thrombocytopenia (ITP) remains enigmatic. B-cell-activating factor (BAFF) and its receptors (BAFF receptor [BAFF-R], transmembrane activator and calcium modulator and cyclophilin ligand interactor [TACI], and B-cell maturation antigen) play central roles in the integrated homeostatic regulation of lymphocytes.

OBJECTIVES

To investigate the pathologic roles of BAFF receptors in regulating the bioactivities of lymphocytes in ITP.

METHODS

An in vitro culture system was established by stimulating CD14(-) peripheral lymphocytes with platelet-preloaded dendritic cells in the presence of recombinant human BAFF (rhBAFF; 20 ng mL(-1)). The functions of BAFF receptors were specifically blocked with blocking antibodies.

RESULTS

BAFF-R, besides prolonging the survival of B cells in both patients and healthy controls, prominently promoted the survival of CD8(+) T cells and the proliferation of B cells in patients with ITP. TACI, as a positive regulator, not only promoted the proliferation of CD4(+) and CD8(+) T cells, but also significantly enhanced the secretion of interleukin-4 in patients with ITP, but not in controls. Besides revealing the pathologic roles of BAFF receptors, these results also indicate that lymphocytes of patients with ITP have enhanced antiapoptotic or proliferative capacity as compared with those from healthy controls when exposed under similar stimulation of rhBAFF. Further study demonstrated that activated autoreactive B cells and CD4(+) T cells from patients with ITP showed significantly higher expression of BAFF-R or TACI than those from healthy controls.

CONCLUSIONS

Both BAFF-R and TACI are pathogenic participants in ITP. Their dysregulated expression in patients with ITP may lead to hyperreactivity of activated autoreactive lymphocytes in response to rhBAFF, and thus is highly significant in the pathogenesis of ITP.

Danazol: an effective option in acquired amegakaryocytic thrombocytopaenic purpura

Acquired amegakaryocytic thrombocytopaenic purpura (AATP) is a rare haematological condition characterised by isolated thrombocytopaenia with normal other cell lines. It is often initially misdiagnosed as immune thrombocytopaenic purpura but has characteristic bone marrow findings of reduced megakaryocyte numbers. The optimal treatment of AATP is not clearly defined but revolves around immunosuppressive therapies. We report a case of successful treatment of AATP with danazol, an antioestrogenic medication. We also review the aetiologies and pathogenesis of the disorder and suggest that danazol should be considered as an effective alternative to potent immunosuppression in AATP.

CD8+ T cells suppress autologous megakaryocyte apoptosis in idiopathic thrombocytopenic purpura

To investigate the effect and mechanism of the CD8+ T cells in bone marrow on autologous megakaryocytopoiesis in idiopathic thrombocytopenic purpura (ITP) patients, we prepared bone marrow mononuclear cells (MNCs) from 15 chronic ITP patients and 13 controls. MNCs were cultured in vitro directly (MNC group) or after depleting CD8+ T cells (CD8+ T-dep group) or adding purified autologous CD8+ T cells to CD8+ T-dep MNCs (Coculture group) or adding dexamethasone to the coculture (DEX group) all in semi-solid and liquid culture systems. The quantity and quality of megakaryocytes were measured. The megakaryocyte count was increased in the presence of autologous CD8+ T cells of patients with chronic ITP, while platelet production was reduced. In addition, lower percentages of polyploidy and apoptotic megakaryocytes, and higher levels of soluble Fas (sFas) in supernatant were observed. Dexamethasone successfully corrected this effect of CD8+ T cells on autologous megakaryocytopoiesis. These studies provide evidence that activated CD8+ T cells in bone marrow of patients with chronic ITP might suppress megakaryocyte apoptosis, leading to impaired platelet production. Megakaryocyte apoptosis would be a novel target for the management of ITP.

Acquired amegakaryocytic thrombocytopenic purpura

Acquired amegakaryocytic thrombocytopenia is an unusual hematologic disorder characterized by thrombocytopenia in association with markedly diminished bone marrow megakaryocytes. We report a case that responded to treatment with cyclosporine but not to IL-11. The bone marrow biopsy, repeated after resolution of thrombocytopenia, showed normal number of megakaryocytes.

Acquired amegakaryocytic thrombocytopenic purpura: review of a not very well-defined disorder

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a hematological disorder characterized by severe thrombocytopenia, probably due to an immunologically induced absence of megakaryocytes with a marked decrease or total absence of megakaryocytes in the bone marrow. AATP may be differentiated from other causes of peripheral destruction of platelets, such as immune thrombocytopenia (ITP). Currently, there are no standard treatments for AATP. However, immunosuppressive therapy including steroids, androgens, anti-thymocyte globulin (ATG), cyclophosphamide, cyclosporine A, immunoglobulins, splenectomy, and allogenic bone marrow transplantation (BMT) have all been utilized with varying degrees of success. However, a positive response in patients with AATP using steroids alone has rarely been reported in the literature.

Acquired amegakaryocytic thrombocytopenia - four cases and a literature review

Acquired amegakaryocytic thrombocytopenla was diagnosed in four dogs. Initial platelet counts in all four dogs were less than 50,000 x 10(9)/litre and initial bone marrow examinations revealed megakaryocytic hypoplasia with minimal changes in the erythroid and myeloid cell lines. Two dogs had evidence of idiopathic immune-mediated disease and two dogs had evidence of associated infectious disease. One dog had a positive antibody titre to Borrella burgdorferi, and one dog had positive titres to both Ehrlichia canis and B. burgdorferi. Treatment consisted of prednisone and cyclophosphamide for the dogs with presumptive immune-mediated disease, and prednisone and tetracycline for the dogs with positive antibody titres to the Infectious organisms. Both dogs with evidence of associated infectious disease responded to treatment. A postmortem examination did not reveal the underlying aetiology in the two dogs with presumptive idiopathic immune-mediated disease.

Acquired pure megakaryocytic aplasia: a separate haematological disease entity or a syndrome with multiple causes?

We report the case of a patient with acquired pure megakaryocytic aplasia. Until today, less than 20 cases of acquired pure megakaryocytic aplasia have been reported and the disease aetiology still seems to be unclear. This report summarizes the published data concerning possible aetiologies, treatment options and outcome of patients with acquired pure megakaryocytic aplasia. Furthermore, this case report presents an example for a possible disease progression.

Autoantibody to c-Mpl (thrombopoietin receptor) in systemic lupus erythematosus: relationship to thrombocytopenia with megakaryocytic hypoplasia

OBJECTIVE

To examine the prevalence, clinical associations, and pathogenic role of autoantibodies to c-Mpl, the thrombopoietin (TPO) receptor, in patients with systemic lupus erythematosus (SLE).

METHODS

Sera from 69 SLE patients, 84 patients with idiopathic thrombocytopenic purpura (ITP), and 60 healthy individuals were screened for anti-c-Mpl antibodies by enzyme-linked immunosorbent assay using recombinant c-Mpl as an antigen. Clinical findings, autoantibody profiles, and serum TPO levels were compared between SLE patients with and without anti-c-Mpl antibodies. A pathogenic role for the anti-c-Mpl antibody was evaluated by examining its inhibitory effect on TPO-dependent cell proliferation and megakaryocyte colony formation.

RESULTS

Serum anti-c-Mpl antibody was detected in 8 SLE patients (11.6%) and 7 ITP patients (8.3%), but in none of the healthy controls. Anti-c-Mpl antibody was associated with thrombocytopenia (P = 0.0002) and a decrease in bone marrow megakaryocytes (P = 0.02) in SLE patients. Serum TPO levels in thrombocytopenic SLE patients with anti-c-Mpl antibodies were significantly elevated compared with levels in those without the antibodies (P = 0.007). IgG fractions purified from anti-c-Mpl antibody-positive sera bound to c-Mpl expressed on the cell surface and inhibited TPO-dependent cell proliferation and megakaryocyte colony formation.

CONCLUSION

Autoantibody to c-Mpl is present in a subset of SLE patients with thrombocytopenia and megakaryocytic hypoplasia. It is likely that the impaired thrombopoiesis in these patients is mediated by the anti-c-Mpl antibody, which functionally blocks an interaction between TPO and c-Mpl.