Bone marrow histopathology of patients with severe aplastic anaemia before treatment and at follow-up

When inflammatory stressors dramatically change, disease phenotypes may transform between autoimmune hematopoietic failure and myeloid neoplasms

Aplastic anemia (AA) and hypoplastic myelodysplastic syndrome are paradigms of autoimmune hematopoietic failure (AHF). Myelodysplastic syndrome and acute myeloid leukemia are unequivocal myeloid neoplasms (MNs). Currently, AA is also known to be a clonal hematological disease. Genetic aberrations typically observed in MNs are detected in approximately one-third of AA patients. In AA patients harboring MN-related genetic aberrations, a poor response to immunosuppressive therapy (IST) and an increased risk of transformation to MNs occurring either naturally or after IST are predicted. Approximately 10%-15% of patients with severe AA transform the disease phenotype to MNs following IST, and in some patients, leukemic transformation emerges during or shortly after IST. Phenotypic transformations between AHF and MNs can occur reciprocally. A fraction of advanced MN patients experience an aplastic crisis during which leukemic blasts are repressed. The switch that shapes the disease phenotype is a change in the strength of extramedullary inflammation. Both AHF and MNs have an immune-active bone marrow (BM) environment (BME). In AHF patients, an inflamed BME can be evoked by infiltrated immune cells targeting neoplastic molecules, which contributes to the BM-specific autoimmune impairment. Autoimmune responses in AHF may represent an antileukemic mechanism, and inflammatory stressors strengthen antileukemic immunity, at least in a significant proportion of patients who have MN-related genetic aberrations. During active inflammatory episodes, normal and leukemic hematopoieses are suppressed, which leads to the occurrence of aplastic cytopenia and leukemic cell regression. The successful treatment of underlying infections mitigates inflammatory stress-related antileukemic activities and promotes the penetration of leukemic hematopoiesis. The effect of IST is similar to that of treating underlying infections. Investigating inflammatory stress-powered antileukemic immunity is highly important in theoretical studies and clinical practice, especially given the wide application of immune-activating agents and immune checkpoint inhibitors in the treatment of hematological neoplasms.

I walk the line: how to tell MDS from other bone marrow failure conditions

Myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell disorders characterized by peripheral cytopenias and ineffective hematopoiesis. MDS is an example of an age-related malignancy and its increasing prevalence and incidence can be attributed to a greater life expectancy in developed countries. Although frequently encountered in hematology/oncology clinics, MDS may constitute a diagnostic challenge especially with equivocal bone marrow morphology. Certain syndromes of bone marrow failure (BMF) may mimic MDS and formulating a correct diagnosis is vital for adequate prognostication as well as therapeutic approaches. Metaphase karyotyping (MK) is a very important diagnostic tool and marker of prognosis and can be an indicator of response to certain therapies. Unfortunately, chromosomal abnormalities may only be found in approximately 50 % of patients with MDS. In this review, we discuss the diagnostic approaches to patients with pancytopenia with a particular focus on the growing number of somatic mutations through new molecular testing.

The challenging world of cytopenias: distinguishing myelodysplastic syndromes from other disorders of marrow failure

Over the past decade, our understanding of bone marrow failure has advanced considerably. Marrow failure encompasses multiple overlapping diseases, and there is increasing availability of diagnostic tools to distinguish among the subtypes. Identification of genetic alterations that underlie marrow failure has also greatly expanded, especially for myelodysplastic syndromes. Molecular markers are increasingly used to guide the management of myelodysplasia and may distinguish this diagnosis from other marrow failure disorders. This review summarizes the current state of distinguishing among causes of marrow failure and discusses the potential uses of multiple diagnostic and prognostic indicators in the management of myelodysplastic syndromes and other bone marrow failure disorders.

S-phase fraction as a useful marker for prognosis and therapeutic response in patients with aplastic anemia

BACKGROUND

The functional definition of aplastic anemia (AA) is the failure of hematopoietic stem cells to proliferate. The aim of the present study was to analyze the S-phase fraction (SPF) (proliferative activity) in patients with AA at diagnosis to explore its relationship with disease characteristics and its value in discriminating among patients with different prognoses. We also investigated whether the SPF value influenced the response to immunosuppressive therapy in AA patients.

PATIENTS AND METHODS

The analysis of SPF at the time of diagnosis was carried out by flow cytometry on peripheral blood samples from 53 consecutive patients with AA and 30 age- and sex-matched controls. All patients were given cyclosporine and followed up periodically to determine response to therapy.

RESULTS

Based on the median SPF, AA patients were divided into two groups: patients with SPF < 0.59% (n = 27) and patients with SPF > 0.59% (n = 26). An SPF > 0.59% was associated with advanced age (P = .02) and elevated serum LDH level (P = .01). Patients with an SPF > 0.59% also had a higher incidence of paroxysmal nocturnal hemoglobinuria and cytogenetic abnormalities. During a median follow-up of 18 months, 3.7% of patients with SPF < or = 0.59 and 11.5% of patients with SPF > 0.59% developed dysplasia and one patient with SPF > 0.59% converted into AML. A significantly higher (P = .018) overall response rate of 53.9% was found in patients with SPF > 0.59% versus 22.2% of patients with SPF < or = 0.59% at 6 months.

CONCLUSIONS

Independently of the peripheral blood count, the SPF at diagnosis may provide information on the expected response to immunosuppressive therapy and the propensity for disease to evolve into MDS/AML. Hence, SPF may serve as an early indicator for the evolution of MDS/AML in patients with AA and thus contribute to therapeutic decisions.

Serial morphologic observation of bone marrow in aplastic anemia in children

Recent reports of myelodysplastic syndrome/acute myeloid leukemia (t-MDS/AML) developing after treatment with immunosuppressants and granulocyte colony-stimulating factor (G-CSF) has raised the question of whether previously unrecognized myelodysplastic features had been present or whether actual transformation had occurred. We undertook a multi-institutional study of 112 children with aplastic anemia diagnosed between 1976 and 1996 and then treated with immunosuppressants with or without G-CSF. In each case, bone marrow specimens were tested at study entry and every 6 months for 3 years to detect t-MDS/AML as defined by morphologic and molecular/cytogenetic criteria. As of December 2001, all eligible patients had been followed for a median of 3 years. Morphologic abnormalities were found in 17 cases. The patients in 4 of these cases had clonal cytogenetic abnormalities and received MDS diagnoses. The morphologic features of the patients with and without clonal cytogenetic abnormalities were indistinguishable. However, the mast cell content was lower in cases with cytogenetic abnormalities than in cases without them. An elucidation of the role of mast cells may provide information about the differences between aplastic anemia and MDS or about the transition of aplastic anemia to MDS.

Hypoplastic myelodysplastic syndrome-a clinical, morphologic, or genetic diagnosis?

We report a middle-aged female with an 11-year history of nonprogressive pancytopenia and severely hypoplastic marrow with minimal morphologic dysplasia. A diagnosis of hypoplastic myelodysplastic syndrome (MDS) was made because of the finding of a persistent clonal abnormality, del(13)(q12q14), and the subsequent demonstration of a single Auer rod-containing blast in the peripheral blood smear. The case illustrates the problems in the differentiation between aplastic anemia and hypoplastic MDS.

Stem cell factor-induced bone marrow mast cell hyperplasia mimicking systemic mastocytosis (SM): histopathologic and morphologic evaluation with special reference to recently established SM-criteria

Although systemic mastocytosis (SM) is a well-defined hematologic neoplasm, it is sometimes difficult to discriminate between SM and a reactive mast cell (MC) hyperplasia. We describe a patient with aplastic anemia who was treated with recombinant stem cell factor (SCF). In response to SCF, the patient showed transient hematologic improvement and developed a marked increase in MC as well as a transient increase in serum tryptase. Histologic and immunohistochemical examination revealed a huge increase in MC in the bone marrow with focal infiltrates similar to SM. However, most of the SM-criteria were not met: First, MC showed normal cytomorphological characteristics without significant atypias (no cytoplasmic extensions, no oval nuclei, no hypogranulated cytoplasm). Furthermore, bone marrow MC were CD2- and CD25-negative and did not exhibit the C-KIT 2468 A-->T mutation (Asp-816-Val). After discontinuation of SCF the MC hyperplasia resolved confirming its reactive nature. Based on our case and similar cases mimicking mastocytosis, it seems of importance to apply recently established SM criteria in order to discriminate between reactive MC hyperplasia and true mastocytosis with certainty.

Myelodysplastic syndrome and aplastic anemia: distinct entities or diseases linked by a common pathophysiology?

It is often difficult to distinguish myelodysplastic syndrome (MDS) from severe aplastic anemia (SAA) because both can present with profoundly hypocellular bone marrows. The distinction matters because although both conditions are complicated by pancytopenia, the risk of progression to acute leukemia is much greater in MDS. This chapter reexamines the relationship between SAA and MDS. The clinical and morphological features and pathophysiology of AA (including moderate and severe forms of acquired AA) are compared with MDS and hypoplastic MDS, with particular reference to new observations implicating autoimmune processes in both conditions. SAA and hypoplastic MDS (HMDS) are discussed in the light of these findings and attempts to separate nonevolving bone marrow failure syndromes from marrow failure progressing to acute leukemia are reviewed. The weight of evidence supports a common pathophysiology and, more speculatively, a common etiology for at least some forms of AA and MDS.

Incidence of aplastic anemia in Turkey: a hospital-based prospective multicentre study

The incidence of aplastic anemia among hospitalized adult patients was prospectively determined in this first study in Turkey. New cases of aplastic anemia among patients 14 years and older who were admitted to the study centers were included in a 3 year survey. Seventy-three patients fulfilled the diagnostic criteria, yielding a mean annual incidence rate of 1.14 cases in 10(3) admissions. The male-to-female ratio of the cases (1.6:1) differed from the almost equal ratio of the larger population of Turkey. The median age was 30 years and females were younger at diagnosis. The age distribution of the cases was different from that of the population; showing two incidence peaks in both sexes. The majority of the patients (89%) had severe disease.

Hypocellular myelodysplastic syndromes (MDS): new proposals

To determine whether hypocellular MDS differs from normo/hypercellular MDS, we attempted to identify hypocellular MDS cases either by correcting the bone marrow (BM) cellularity by age (28 patients) or by using a single arbitrary value of BM cellularity (25 patients) and compared these two groups of hypocellular cases to the normo/hypercellular MDS cases (72 patients). 18 patients were common to both hypocellular groups. Patients with hypocellular MDS in both of these selected groups have similar features with regard to age and sex distribution, peripheral blood and bone marrow parameters, FAB subtypes, karyotypes, leukaemic transformation, and survival. However, the median age of patients in < 30% BM cellularity group was higher than those patients in the age-corrected group (69 years v 62 years). The selection of < 30% cellularity excluded 10 cases in the age group < 70 years but included another seven patients in the age group of > 70 years. However, correction of BM cellularity by age revealed that those included patients (selected for < 30% cellularity) who had normocellular BM by their age. Therefore we recommend the age-correcting grouping to ensure comparable series for comparison, for response to treatment, and survival. Finally, BM cellularity does not appear to be an important factor on prognosis in MDS, because patients with hypocellular MDS in both selected groups have similar prognosis to those with normo/hypercellular MDS patients.

Hypoplastic myelodysplastic syndrome: incidence, morphology, cytogenetics, and prognosis

The present study, based upon the retrospective evaluation of 352 patients with primary myelodysplastic syndrome (pMDS), revealed hypoplastic MDS in 42 patients (11.9%). Median age is similar in hypo- and normo-/hypercellular MDS (72.6 versus 70.7 versus 72.4 years). Hypoplastic MDS occurred significantly more often in women compared with normo- and hypercellular MDS. Sequential biopsies were performed in 14 patients, showing a persistence of hypoplasia over a period of up to 43 months. The proportion of patients showing mesenchymal reaction, especially an increase of mast cells, was significantly higher in hypoplastic MDS, whereas dysplastic features of hematopoiesis occurred less frequently and were of lower grade in comparison to normo-/hyperplastic MDS. Among the subgroup with hypoplastic bone marrow, the classification according to FAB criteria revealed 28 patients with RA (66.7%), three with RARS (7.1%), and eight with RAEB (19.0%), as well as one patient each with RAEB-T and CMMol (2.4% each), and one case which had to be reckoned among the category of unclassifiable MDS (2.4%). Median survival was 21.8 months for hypoplastic MDS, 26.9 months for normoplastic MDS, and 14.2 months for hyperplastic MDS. During follow-up, 14 patients (33%) with hypoplastic MDS developed acute nonlymphatic leukemia. Although not a constant finding, karyotype abnormalities involving particularly chromosome 7 seem to be associated with hypoplastic MDS. The results confirm the existence of a hypoplastic variant of MDS which seems to more frequently affect female patients, and which requires bone marrow biopsy for its accurate diagnosis.

Diagnoses in patients with severe pancytopenia suspected of having aplastic anemia

There were 100 patients with pancytopenia notified to the Swedish part of an international study of aplastic anemia (Aa) (1983-1986). Aa was the cause in 16 patients and 50 patients had different conditions explaining their pancytopenia, whereas in 34 patients no obvious explanation was found at the time of discovery of their pancytopenia. A follow-up study in 1987 comprised the patients with Aa (n = 16) and the patients with uncharacterized pancytopenia (n = 34.3 additional patients had then been diagnosed as having Aa whereas 3 patients had a diagnosis of a low-grade NHL and 8 patients a diagnosis of MDS. No (or an inadequate) bone marrow sample had been taken in 9 of the 34 patients. This study shows that pancytopenia may be found in many serious conditions. Patients with pancytopenia should be carefully followed as Aa can develop slowly and as the MDS diagnosis can be difficult to establish at an early stage.