The ratio of bone marrow myeloid progenitor cell proportion to mature lymphocytes proportion can effectively differentiate aplastic anemia and hypoplastic myelodysplastic syndrome and evaluate the quality of bone marrow aspirates.

INTRODUCTION: Aplastic anemia (AA) and hypoplastic myelodysplastic syndrome (MDS-h) are bone marrow failure disease and difficult to distinguish merely by morphological analysis. In this study, we investigated the value of flow cytometry (FCM) in the differential diagnosis of AA and MDS-h. METHODS: We included 822 patients (626 control, 69 AA, 22 MDS-h and 105 dilution patients) from January 2017 to December 2022 for a retrospective study. Bone marrow myeloid progenitor (MP) cell and mature lymphocytes proportions were analyzed by FCM. The ratio of MP cell proportion and mature lymphocytes proportion, MPLR, was calculated. Data were compared by Kruskal-Wallis test. Differential diagnostic efficacy was evaluated by receiver operating characteristic (ROC) curve. Cutoff value was determined by the maximum Youden index. RESULTS: Bone marrow MP cell proportion and MPLR of MDS-h patients were higher than AA patients. Mature lymphocytes proportion of MDS-h patients was lower than AA patients. Area under ROC curve (AUC of ROC) of MP cell proportion, MPLR and mature lymphocytes proportion to distinguish AA from MDS-h were 0.992, 0.988, and 0.850, respectively. Moreover, MPLR of dilution patients was higher than AA patients but lower than MDS-h patients. The AUC of ROC curves of MPLR to distinguish MDS-h and AA from dilution were 0.854 and 0.871, respectively. CONCLUSION: Bone marrow MP cell proportion and MPLR can effectively discriminate AA from MDS-h with similar differential efficacy, which is higher than mature lymphocytes proportion. Moreover, MPLR can evaluate the quality of bone marrow aspirates, which would interfere with the differential diagnosis.

[Deciphering Hypoplastic Myelodysplastic Syndrome and Aplastic Anemia via In-Depth Analysis of Lymphocyte Subsets].

OBJECTIVE: To explore the difference of lymphocyte subsets in peripheral blood (PB) between aplastic anemia (AA) and hypoplastic myelodysplastic syndrome (hypo-MDS) patients, meanwhile to compare the clinical parameters obtained from PB and bone marrow (BM). METHODS: The lymphocyte subsets in hypo-MDS (n=25) and AA (n=33) patients were investigated by flow cytometry. Meanwhile, the differences in PB cell counts, biochemical indicators, BM cell counts and abnormal chromosomes between the two groups were analyzed. RESULTS: The percentage of CD8+T cells in AA group was significantly higher than that in hypo-MDS group (P=0.001), while the percentage of CD4+ T cells and the CD4+/CD8+ ratio in AA group were obviously lower than those in hypo-MDS group (P=0.015 and 0.001, respectively). Furthermore, the proportion of CD4+ and CD8+ activated T (TA) cells, and memory Tregs in AA group was distinctly lower than those in hypo-MDS group (P=0.043, 0.015 and 0.024, respectively). Nevertheless, the percentage of CD8+ naive T (TN) cells in AA patients was remarkably higher (P=0.044). And hypo-MDS patients had declined lymphocyte counts (P=0.025), increased levels of total bilirubin (TBil), lactate dehydrogenase (LDH), vitamin B12 and proportion of BM blasts than AA patients (P=0.019, 0.023, 0.027 and 0.045, respectively). CONCLUSION: In this study it was confirmed that the percentages of CD4+ and CD8+ TA cells, memory Tregs and CD8+ TN cells were significantly different between AA and hypo-MDS patients, which provide an essential basis for the identification of these two diseases.

Hypoplastic myelodysplastic syndrome and acquired aplastic anemia: Immune­mediated bone marrow failure syndromes (Review).

Hypoplastic myelodysplastic syndrome (hMDS) and aplastic anemia (AA) are rare hematopoietic disorders characterized by pancytopenia with hypoplastic bone marrow (BM). hMDS and idiopathic AA share overlapping clinicopathological features, making a diagnosis very difficult. The differential diagnosis is mainly based on the presence of dysgranulopoiesis, dysmegakaryocytopoiesis, an increased percentage of blasts, and abnormal karyotype, all favouring the diagnosis of hMDS. An accurate diagnosis has important clinical implications, as the prognosis and treatment can be quite different for these diseases. Patients with hMDS have a greater risk of neoplastic progression, a shorter survival time and a lower response to immunosuppressive therapy compared with patients with AA. There is compelling evidence that these distinct clinical entities share a common pathophysiology based on the damage of hematopoietic stem and progenitor cells (HSPCs) by cytotoxic T cells. Expanded T cells overproduce proinflammatory cytokines (interferon­Î³ and tumor necrosis factor­α), resulting in decreased proliferation and increased apoptosis of HSPCs. The antigens that trigger this abnormal immune response are not known, but potential candidates have been suggested, including Wilms tumor protein 1 and human leukocyte antigen class I molecules. Our understanding of the molecular pathogenesis of these BM failure syndromes has been improved by next­generation sequencing, which has enabled the identification of a large spectrum of mutations. It has also brought new challenges, such as the interpretation of variants of uncertain significance and clonal hematopoiesis of indeterminate potential. The present review discusses the main clinicopathological differences between hMDS and acquired AA, focuses on the molecular background and highlights the importance of molecular testing.

Immunologic effects on the haematopoietic stem cell in marrow failure.

Acquired bone marrow failure (BMF) syndromes comprise a diverse group of diseases with variable clinical manifestations but overlapping features of immune activation, resulting in haematopoietic stem and progenitor cells (HSPC) damage and destruction. This review focuses on clinical presentation, pathophysiology, and treatment of four BMF: acquired aplastic anaemia, large granular lymphocytic leukaemia, paroxysmal nocturnal haemoglobinuria, and hypoplastic myelodysplastic syndrome. Autoantigens are speculated to be the inciting event that result in immune activation in all of these diseases, but specific pathogenic antigens have not been identified. Oligoclonal cytotoxic T cell expansion and an active role of proinflammatory cytokines, primarily interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α), are two main contributors to HSPC growth inhibition and apoptosis in BMF. Emerging evidence also suggests involvement of the innate immune system.

Hypoplastic Myelodysplastic Syndromes: Just an Overlap Syndrome?

: Myelodysplasias with hypocellular bone marrow (hMDS) represent about 10-15% of MDS and are defined by reduced bone marrow cellularity (i.e., <25% or an inappropriately reduced cellularity for their age in young patients). Their diagnosis is still an object of debate and has not been clearly established in the recent WHO classification. Clinical and morphological overlaps with both normo/hypercellular MDS and aplastic anemia include cytopenias, the presence of marrow hypocellularity and dysplasia, and cytogenetic and molecular alterations. Activation of the immune system against the hematopoietic precursors, typical of aplastic anemia, is reckoned even in hMDS and may account for the response to immunosuppressive treatment. Finally, the hMDS outcome seems more favorable than that of normo/hypercellular MDS patients. In this review, we analyze the available literature on hMDS, focusing on clinical, immunological, and molecular features. We show that hMDS pathogenesis and clinical presentation are peculiar, albeit in-between aplastic anemia (AA) and normo/hypercellular MDS. Two different hMDS phenotypes may be encountered: one featured by inflammation and immune activation, with increased cytotoxic T cells, increased T and B regulatory cells, and better response to immunosuppression; and the other, resembling MDS, where T and B regulatory/suppressor cells prevail, leading to genetic clonal selection and an increased risk of leukemic evolution. The identification of the prevailing hMDS phenotype might assist treatment choice, inform prognosis, and suggest personalized monitoring.

Next-generation sequencing in hypoplastic bone marrow failure: What difference does it make?

Hypoplastic bone marrow failure is a diagnostic feature of multiple haematological disorders, which also share a substantial overlap of clinical symptoms. Hence, discrimination of underlying disorders in patients presenting with hypoplastic bone marrow failure remains a major challenge in the clinic. Recent next-generation sequencing (NGS) studies have broadened our understanding of the varying molecular mechanisms and advanced diagnostics of disorders exhibiting hypoplastic bone marrow failure. In this article, we present a literature review of NGS studies of haematological disorders associated with hypoplastic bone marrow failure and highlight the relevance of NGS for improved clinical diagnostics and decision-making.

Comparison of T lymphocyte subsets in aplastic anemia and hypoplastic myelodysplastic syndromes.

AIMS: This study aims to compare the proportion of peripheral blood T lymphocyte subsets and related blood cell and bone marrow cytology indexes between patients with aplastic anemia (AA) and hypoplastic myelodysplastic syndrome (hypo-MDS), and investigate the clinical identification significance. MATERIALS AND METHODS: A total of 41 patients with AA and 46 patients with hypo-MDS were collected, and the proportions of peripheral blood T lymphocyte subsets, CD3-CD16/CD56+NK cells, CD3+CD57+T-LGL cells and CD19+B lymphocytes were detected by flow cytometry. KEY FINDINGS: The CD4+/CD8+ ratio decreased in the AA and hypo-MDS groups, and the difference was statistically significant when compared with that in the control group (P<0.05). However, there was no significant difference between AA and hypo-MDS groups (P>0.05). The proportions of CD3-CD16/CD56+NK cells and CD3+CD57+T-LGL cells in the hypo-MDS group were distinctly higher than those in the AA group (P<0.05). However, the proportion of CD19+B lymphocyte was obviously lower than that in the AA group (P<0.05). Furthermore, the proportions of reticulocytes, bone marrow progenitor cells and immature red blood cells in the hypo-MDS group were significantly more than those in the AA group (P<0.05), and the proportion of mature lymphocytes in the hypo-MDS group was distinctly lower than that in the AA group (P<0.05). SIGNIFICANCE: Changes of T lymphocyte subsets and the proportions of large granular lymphocytes and B lymphocytes can be utilized as indexes in the differential diagnosis between AA and hypo-MDS.

Immunological derangement in hypocellular myelodysplastic syndromes.

Hypocellular or hypoplastic myelodysplastic syndromes (HMDS) are a distinct subgroup accounting for 10-15% of all MDS patients, that are characterized by the presence of bone marrow (BM) hypocellularity, various degree of dysmyelopoiesis and sometimes abnormal karyotype. Laboratory and clinical evidence suggest that HMDS share several immune-mediated pathogenic mechanisms with acquired idiopathic aplastic anemia (AA). Different immune-mediated mechanisms have been documented in the damage of marrow hematopoietic progenitors occurring in HMDS; they include oligoclonal expansion of cytotoxic T lymphocytes (CTLs), polyclonal expansion of various subtypes of T helper lymphocytes, overexpression of FAS-L and of the TNF-related apoptosis-inducing ligand (TRAIL), underexpression of Flice-like inhibitory protein long isoform (FLIPL) in marrow cells as well as higher release of Th1 cytokines, such as interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α). It has also been documented that some HMDS patients have higher frequency of polymorphisms linked both to high production of proinflammatory cytokines such as TNF-α and transforming growth factor-ß and to the inhibition of T-cell mediated immune responses such as interleukin-10, further suggesting that immune-mediated mechanisms similar to those seen in AA patients may also operate in HMDS. Clinically, the strongest evidence for immune-mediated hematopoietic suppression in some HMDS is the response to immunosuppression including mainly cyclosporine, anti-thymocyte globulin and/or cyclosporine, or alemtuzumab. Here we review all these immune mechanisms as well as the influence of this deranged cellular and humoral immunologic mileau on the initiation and possible progression of MDS. All these observations are pivotal not only for a better understanding of MDS pathophysiology, but also for their immediate clinical implications, eventually leading to the identification of MDS patients who may benefit from immunosuppression.