Acquired Amegakaryocytic Thrombocytopenic Purpura Research Articles

Acquired Amegakaryocytic Thrombocytopenic Purpura: A Review of Therapeutic Options.

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a rare bone marrow disorder characterized by either a marked decrease or a complete absence of megakaryocytes with the preservation of all other cell lines. To date, more than 60 cases of AATP have been reported in the literature. Due to the rarity of this disease, no standard treatment guidelines have been established, and therapy is based on a handful of case studies and expert opinions. Herein, we provide a comprehensive review of currently utilized therapeutic options for AATP.

Acquired Amegakaryocytic Thrombocytopenic Purpura Associated with a Paroxysmal Nocturnal Hemoglobinuria Clone: A Case Report and Review of the Literature

Background: Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a rare bone marrow disorder characterized by a marked reduction in megakaryocytes with otherwise normal hematopoiesis. Both humoral and cell-mediated suppression of megakaryocytopoeisis have been postulated as mechanisms causing AATP. Herein we report a case of a 67-year-old man diagnosed with AATP with a co-existent paroxysmal nocturnal hemoglobinuria (PNH) clone and review the literature on AATP, focusing on proposed etiologies for this rare condition. Case: A 67-year-old man presented to clinic with a 1-week history easy bruising, petechiae and a platelet count of 6 x 109/L. He had a history of left elbow bursitis caused by S. pyogenes, treated with antibiotics 6-months prior to his presentation. His CBC was normal at that time. On assessment, HIV, HBV, HCV, and H. pylori serologies were negative; CMV and EBV serologies were positive for IgG and negative for IgM. ANA and RF were negative, and vitamin B12 level was normal. There was no hepatosplenomegaly on ultrasound. Bone marrow aspirate and biopsy demonstrated a normocellular marrow with severe megakaryocytic hypoplasia. Cytogenetics demonstrated normal male karyotype with loss of Y chromosome in 9/20 metaphases. Flow cytometry revealed a population of 3.99% GPI-deficient neutrophils by FLAER assay. Molecular testing for myeloid mutations and T-cell gene rearrangement is pending. The patient was initially treated with corticosteroids and IVIG, and showed no response with persistent isolated thrombocytopenia. He was managed with platelet transfusions which resulted in a normal platelet increment of 35 x 109/L 1-hour post-transfusion. A diagnosis of AATP was established and he was admitted for immunosuppressive therapy (IST) with ATG and cyclosporine. Methods: We conducted a narrative review of the literature on AATP, searching MEDLINE and EMBASE for articles on AATP published in English between 1946 and 2020. Reference lists of selected articles were reviewed to identify additional cases. We extracted data on presentation, bone marrow findings (including cytogenetics, molecular genetics, and flow cytometry), treatment regimens and outcomes. Results: We identified 47 cases of adult patients with thrombocytopenia attributed to AATP reported in the literature (Table 1). Three main mechanisms were proposed: (i) cell-mediated autoimmunity, (ii) humoral autoimmunity, and (iii) intrinsic stem cell defect. All three mechanisms were supported by in vitro studies, which demonstrated suppression of colony forming unit-megakaryocytes (CFU-M) by patients' T-lymphocytes (Gerwitz et al. 1986; Colovic et al. 2004) and serum (Hoffman et al. 1982) found to contain IgG antibodies inhibiting CFU-M formation, as well as intrinsic defects in CFU-M progenitor proliferation. Few studies reported cytogenetic abnormalities and only one documented molecular genetic testing. Response to IST was reported in several cases, most commonly ATG and cyclosporine. Four recent cases demonstrated remission following treatment with TPO agonists eltrombopag and romiplostim. Six cases progressed to aplastic anemia and 4 to myelodysplastic syndrome (MDS). Flow cytometry results were not reported in the majority of cases, and only 1 case reported coexistence of a PNH clone, identified in a pregnant patient with AATP (Zimmerman et al. 2019). Discussion: AATP is defined as severe thrombocytopenia with bone marrow showing marked decrease or absence of megakaryocytes with preservation of other cell lineages. This broad definition encompasses a range of causes, and our review of the literature highlights the heterogenous nature of AATP which has several proposed mechanisms and a number of therapeutic options. The best evidence suggests that AATP is often secondary to T-cell-mediated suppression of megakaryocytopoeisis, which has been demonstrated by in vitro studies, and is supported in vivo by a case of AATP following PD-1 inhibition (Iyama et al. 2020), and frequent response of AATP to T-cell-directed IST. The co-existence of a PNH clone in our case lends further support to a T-cell-mediated autoimmune process, analogous to the mechanism described in aplastic anemia and hypoproliferative MDS. The application of molecular diagnostics may help to further elucidate the role of clonal hematopoiesis and intrinsic stem cell defects versus humoral and cell-mediated autoimmunity in AATP. Disclosures No relevant conflicts of interest to declare.

Acquired amegakaryocytic thrombocytopenic purpura with literature review

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is an uncommon disorder with thrombocytopenia and selectively suppressed megakaryopoiesis, often mistaken as immune thrombocytopenic purpura (ITP). It usually does not respond to steroids, and bone marrow examination shows complete absence of megakaryocytes. The treatment and prognosis of AATP vary greatly from ITP; therefore, it is important to diagnose and treat this condition early, as it can progress rapidly to complete bone marrow failure. In this case report, we report a patient with AATP responded well to cyclosporine therapy.

Acquired Amegakaryocytic Thrombocytopenic Purpura - An Underdiagnosed Entity

Acquired Amegakaryocytic Thrombocytopenic Purpura (AATP) is a rare cause of thrombocytopenia presenting over a wide age group with symptoms of bleeding and bone marrow showing isolated absence of megakaryocytes in an otherwise normal marrow. Here, we report a case of AATP in a three year old female child who was then treated with anti thymocyte globulin successfully. We report this case because of it's under diagnosis or misdiagnosis as immune thrombocytopenia (ITP) in most of the cases. We also review the literature regarding the pathogenesis and treatment of this undiagnosed entity.

Megakaryocyte Colony-Forming Units (CFU-Meg) Growth Is Enhanced by Alemtuzumab Mediated Lymphocyte Depletion: In Vitro Experiments and a Case Report of Acquired Amegakaryocytic Thrombocytopenic Purpura.

Background. Alemtuzumab (Ale) induces destruction of CD52 antigen-bearing cells by antibody-dependent cell-mediated lysis, complement-mediated lysis, and induction of apoptosis. As a potent T cell depleting agent, Ale is used also for GvHD prophylaxis, given either i.v. around the time of transplantation, or directly "in the bag" to the cell suspension containing hematopoietic stem cells and lymphocytes. Contrary to bone marrow-derived grafts, the experience with addition of Ale to the peripheral blood progenitor cells (PBPC) suspension is limited. Therefore, we decided to study the effect of short-time incubation of PBSC samples with Ale using flow-cytometry and cultivation assays.Methods. After an informed consent, a sample of PBSC product (15 mL) was obtained from the collection bag immediately after a leukapheresis (COBE Spectra) in 8 healthy donors mobilized by G-CSF. Cells were washed using 4% human albumin and then incubated at 37°C with 1) Ale at the dose of 5 μg/106 cells, and 2) water for injection as a control. Autologous plasma as a source of complement was added after 15 min of incubation and cells suspensions were further incubated for 15 minutes. Both cell suspensions were then washed, resuspended in 4% human albumin, and samples were collected for blood count, flow-cytometric analysis, and cultivation assays (CFU-GM, BFU-E, CFU-Meg).Results. As expected, Ale caused profound T-cell (by a median of 99.3% vs. 12.3% in control) as well as marked B-cell (by a median of 90.6% vs. 8.3% in control) depletion. CD4+ and CD8+ lymphocytes were eliminated equally by a median of 99.5%, and 99.1%, respectively. Ale also produced a moderate reduction of CFU-GM and BFU-E (by a median of 37.7% vs. 3.3%, and 49.7% vs. 10.8%, respectively). NK-cells were not significantly affected as well as granulocytes and monocytes. Surprisingly, incubation with Ale clearly enhanced the growth of CFU-Meg; in median 8-times more CFU-Meg were observed in samples after incubation with Ale comparing to control samples (from 3 to 21-times, p<0.01). Based on these findings we decided to use Ale for the treatment of 63-year-old woman suffering from severe and therapy resistant (steroids, cyclosporine A) acquired amegakaryocytic thrombocytopenic purpura (AATP). Patient's bone marrow samples were first tested as described above and a remarkable enhancement of CFU-Meg growth (106 CFU-Meg/1 ml of bone marrow) was observed in a sample incubated with Ale comparing to a control sample not incubated with Ale (2.4 CFU-Meg/1 ml of bone marrow). The patient subsequently received Ale at the dose of 10 mg 3 times weekly for 3 weeks. Ale administration had to be temporarily discontinued for CMV reactivation; however, platelets count significantly increased from 10x109/L to 50x109/L.Conclusion. Our results demonstrate that megakaryopoiesis is physiologically suppressed by lymphocytes. To the best of our knowledge, this is the first description that profound lymphocyte depletion by Ale enhances megakaryopoiesis in vitro and that Ale can also be used in vivo for the treatment of AATP.

Acquired amegakaryocytic thrombocytopenic purpura with a Philadelphia chromosome

A 30-year-old Chinese man with acquired amegakaryocytic thrombocytopenic purpura (AATP) and a Ph chromosome is reported. At presentation, he had severe thrombocytopenia resulting in epistaxis, gingival bleeding, and ecchymoses, while other hematologic values were within the normal range. Bone marrow aspiration showed no megakaryocytes, with a normal appearance of erythroblastic and granulopoietic series. He failed to respond to prednisone treatment, and underwent a progress from isolated thrombocytopenia to full pancytopenia. At last he died of spontaneous intracranial hemorrhage. An in vitro culture for granulocyte-macrophage precursors showed very few colonies. Karyotypic analysis revealed a standard Ph chromosome translocation, t(9;22)(q34;q11), in the majority of bone marrow cells. Southern blot analysis using a 3′ bcr-HE probe didn't detect a rearrangement within the bcr DNA sequence. This patient, in fact, was a myelodysplastic disorder, initially presenting as AATP. The diagnosis of chronic myelogenous leukemia was excluded on the basis of clinical and hematologic findings. The heterogeneity of Ph chromosome in myelodysplastic syndrome is discussed.

Amegakaryocytic thrombocytopenia of 4 years duration: Successful treatment with antithymocyte globulin

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a rare cause of thrombocytopenia. Since it is a syndrome of diverse etiologies, the optimal treatment is often uncertain. In a patient with longstanding AATP, a complete remission was obtained with antithymocyte globulin.

Acquired Amegakaryocytic Thrombocytopenic Purpura Associated with Immunoglobulin Deficiency

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a haematological disorder characterized by severe thrombocytopenia due to an immunologically induced absence of megakaryocytes in an otherwise normal-appearing bone marrow. A 57-year-old male with a 6-month history of rectal and cutaneous bleeding is reported. Platelet count was 10 X 10(9)/l, while other haematological values were within the normal range, except for the presence of hypogammaglobulinaemia with decreased IgA and IgG. Both platelet median volume and half-life span were normal, and antiplatelet IgG determinations were negative. Bone marrow aspiration and biopsy showed no megakaryocytes, with a normal appearance of erythroblastic and granulopoietic series. An in vitro culture for megakaryocytic progenitor cells did not show any growth of megakaryocyte colonies. No inhibitory effect on the growth of normal marrow megakaryocytic colonies was observed when serum and lymphocytes of the patient were added. Following 4 weeks of prednisone therapy, the platelet count rose to 127 X 10(9)/l and the bone marrow aspirate showed some megakaryocytes. The possible pathogenetic mechanisms of this entity are discussed.

Cell-Mediated Suppression of Megakaryocytopoiesis in Acquired Amegakaryocytic Thrombocytopenic Purpura

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a disorder of hematopoiesis characterized by severe thrombocytopenia due to a selective reduction or total absence of megakaryocytes in an otherwise normal-appearing bone marrow. Although the development of autoantibodies directed against cells in the megakaryocyte progenitor cell pool has been implicated in the pathogenesis of this disorder, cell-mediated suppression of megakaryocytopoiesis has not been described. Accordingly, we report two cases of AATP in which in vitro suppression of megakaryocyte colony formation by autologous ancillary marrow cells was demonstrable. Light-density bone marrow mononuclear cells (MNCs) obtained from both patients were either plated directly into plasma clot cultures, or after first being depleted by adherent monocytes (M phi) or T lymphocytes using standard methodologies. In some experiments, the depleted ancillary marrow cells were recovered for autologous co-culture studies with the MNCs from which they had been depleted. Megakaryocyte colony formation was detected in the cultures using an indirect immunofluorescence assay with a rabbit anti-human platelet glycoprotein antiserum. Removal of M phi (n = 6), or T lymphocytes (n = 4) from normal marrow MNCs had no apparent effect on colony formation. In contrast, depleting T lymphocytes from the MNCs of patient 1 significantly augmented megakaryocyte colony formation; a similar effect was observed after depleting M phi from the MNCs of patient 2. This observed augmentation in colony formation could be abrogated by autologous co-culture with the putative suppressor cell at effector cell/target cell ratios of 1:10 in the case of T lymphocytes or 1:5 in the case of M phi. Neither suppression nor stimulation of megakaryocyte colony formation was observed after culturing normal MNCs with autologous T cells (n = 4) or M phi (n = 3) at similar or greater ratios. We also observed inhibition of megakaryocyte colony formation after culturing normal MNCs in the presence of tissue culture medium conditioned by the M phi of patient 2. This effect was shown to be specific for megakaryocytes since this same conditioned medium had no significant effect on BFU-E and CFU-E-derived colony formation by autologous marrow mononuclear cells. These results suggest that: both T cells and M phi are capable of exerting a regulatory effect on the proliferation of human megakaryocyte progenitor cells (CFU-Meg); in the case of M phi, a soluble factor elaborated by these cells may be responsible for suppressing CFU-Meg growth; and aberrant ancillary cell-megakaryocyte progenitor cell interactions may lead to clinically significant disease.

Cell-mediated suppression of megakaryocytopoiesis in acquired amegakaryocytic thrombocytopenic purpura

Acquired amegakaryocytic thrombocytopenic purpura (AATP) is a disorder of hematopoiesis characterized by severe thrombocytopenia due to a selective reduction or total absence of megakaryocytes in an otherwise normal-appearing bone marrow. Although the development of autoantibodies directed against cells in the megakaryocyte progenitor cell pool has been implicated in the pathogenesis of this disorder, cell-mediated suppression of megakaryocytopoiesis has not been described. Accordingly, we report two cases of AATP in which in vitro suppression of megakaryocyte colony formation by autologous ancillary marrow cells was demonstrable. Light-density bone marrow mononuclear cells (MNCs) obtained from both patients were either plated directly into plasma clot cultures, or after first being depleted by adherent monocytes (M phi) or T lymphocytes using standard methodologies. In some experiments, the depleted ancillary marrow cells were recovered for autologous co-culture studies with the MNCs from which they had been depleted. Megakaryocyte colony formation was detected in the cultures using an indirect immunofluorescence assay with a rabbit anti- human platelet glycoprotein antiserum. Removal of M phi (n = 6), or T lymphocytes (n = 4) from normal marrow MNCs had no apparent effect on colony formation. In contrast, depleting T lymphocytes from the MNCs of patient 1 significantly augmented megakaryocyte colony formation; a similar effect was observed after depleting M phi from the MNCs of patient 2. This observed augmentation in colony formation could be abrogated by autologous co-culture with the putative suppressor cell at effector cell/target cell ratios of 1:10 in the case of T lymphocytes or 1:5 in the case of M phi. Neither suppression nor stimulation of megakaryocyte colony formation was observed after culturing normal MNCs with autologous T cells (n = 4) or M phi (n = 3) at similar or greater ratios. We also observed inhibition of megakaryocyte colony formation after culturing normal MNCs in the presence of tissue culture medium conditioned by the M phi of patient 2. This effect was shown to be specific for megakaryocytes since this same conditioned medium had no significant effect on BFU-E and CFU-E-derived colony formation by autologous marrow mononuclear cells. These results suggest that: both T cells and M phi are capable of exerting a regulatory effect on the proliferation of human megakaryocyte progenitor cells (CFU-Meg); in the case of M phi, a soluble factor elaborated by these cells may be responsible for suppressing CFU-Meg growth; and aberrant ancillary cell- megakaryocyte progenitor cell interactions may lead to clinically significant disease.

Acquired Amegakaryocytic Thrombocytopenic Purpura: A Syndrome of Diverse Etiologies

AbstractThe possible pathogenetic mechanisms responsible for the production of acquired amegakaryocytic thrombocytopenic purpura (AATP) were investigated in a group of patients with this disorder. Absence of megakaryocytes and small platelet glycoprotein-bearing mononuclear cells, as determined by immunochemical staining of patient marrows with an antisera to platelet glycoproteins, suggested that the defect in AATP occurs in an early progenitor cell of the megakaryocytic lineage. Using an in vitro clonal assay system for megakaryocytic progenitor cells or megakaryocyte colony-forming units (CFU-M), the proliferative capacity of AATP marrow cells was then assessed. Bone marrow cells from three of four patients formed virtually no megakaryocyte colonies, suggesting that in these individuals the AATP was due to an intrinsic defect in the CFU-M. Bone marrow cells from an additional patient, however, formed 12% of the normal numbers of colonies, providing evidence for at least partial integrity of the CFU-M compartment in this patient. Serum specimens from all six patients were screened for their capacity to alter in vitro megakaryocyte colony formation. Five of six sera enhanced colony formation in a stepwise fashion, demonstrating appropriately elevated levels of megakaryocyte colony-stimulating activity. The serum of the patient with partial integrity of the CFU-M compartment, however, stimulated colony formation only at low concentrations. At higher concentrations, this patient’s serum actually inhibited the number of colonies cloned, suggesting the presence of a humoral inhibitor to CFU-M. Serum samples from all patients were further screened for such humoral inhibitors of megakaryocyte colony formation using a cytotoxicity assay. The patient whose serum was inhibitory to CFU-M at high concentrations was indeed found to have a complement-dependent serum IgG inhibitor that was cytotoxic to allogeneic and autologous marrow CFU-M but did not alter erythroid colony formation. These studies suggest that AATP can be due to at least two mechanisms: either an intrinsic defect at the level of the CFU-M or a circulating cytotoxic autoantibody directed against the CFU-M.

Acquired amegakaryocytic thrombocytopenic purpura: a syndrome of diverse etiologies

The possible pathogenetic mechanisms responsible for the production of acquired amegakaryocytic thrombocytopenic purpura (AATP) were investigated in a group of patients with this disorder. Absence of megakaryocytes and small platelet glycoprotein-bearing mononuclear cells, as determined by immunochemical staining of patient marrows with an antisera to platelet glycoproteins, suggested that the defect in AATP occurs in an early progenitor cell of the megakaryocytic lineage. Using an in vitro clonal assay system for negakaryocytic progenitor cells or megakaryocyte colony-forming units (CFU-M), the proliferative capacity of AATP marrow cells was then assessed. Bone marrow cells from three of four patients formed virtually no megakaryocyte colonies, suggesting that in these individuals the AATP was due to an intrinsic defect in the CFU-M. Bone marrow cells from an additional patient, however, formed 12% of the normal numbers of colonies, providing evidence for at least partial integrity of the CFU-M compartment in this patient. Serum specimens from all six patients were screened for their capacity to alter in vitro megakaryocyte colony formation. Five of six sera enhanced colony formation in a stepwise fashion, demonstrating appropriately elevated levels of megakaryocyte colony- stimulating activity. The serum of the patient with partial integrity of the CFU-M compartment, however, stimulated colony formation only at low concentrations. At higher concentrations, this patient's serum actually inhibited the number of colonies cloned, suggesting the presence of a humoral inhibitor to CFU-M. Serum samples from all patients were further screened for such humoral inhibitors of megakaryocyte colony formation using a cytotoxicity assay. The patient whose serum was inhibitory to CFU-M at high concentrations was indeed found to have a complement-dependent serum IgG inhibitor that was cytotoxic to allogeneic and autologous marrow CFU-M but did not alter erythroid colony formation. These-studies suggest that AATP can be due to at least two mechanisms: either an intrinsic effect at the level of the CFU-M or a circulating cytotoxic autoantibody directed against the CFU-M.