MDS/MPN-RS-T justified inclusion as a unique disease entity?

Myelodysplastic syndrome/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) is a disease entity characterized by anemia, bone marrow dysplasia with ring sideroblasts and persistent thrombocytosis ≥450 × 109/L with proliferation of large and morphologically atypical megakaryocytes. Although initially recognized by the World Health Organization only as a provisional entity, next generation sequencing has identified recurrent somatic mutations in SF3B1, JAK2 and other genes providing further evidence of the clonal nature of this disease and the need to recognize it as a separate entity. Despite its overlapping features with MDS with ring sideroblasts and essential thrombocythemia, MDS/MPN-RS-T is characterized by specific clinical features and distinct survival outcomes. In the current review we will describe the morphological and genomic features of MDS-RS-T and the potential diagnostic challenges and distinction from other possible conditions. We will also review how the current evidence supports its recognition as an independent disorder.

Refractory anemia with ring sideroblasts (RARS) and RARS with thrombocytosis (RARS-T): 2017 update on diagnosis, risk-stratification, and management.

DISEASE OVERVIEW: Ring sideroblasts (RS) are erythroid precursors with abnormal perinuclear mitochondrial iron accumulation. Two myeloid neoplasms defined by the presence of RS, include refractory anemia with ring sideroblasts (RARS), now classified under myelodysplastic syndromes with RS (MDS-RS) and RARS with thrombocytosis (RARS-T); now called myelodysplastic/myeloproliferative neoplasm with RS and thrombocytosis (MDS/MPN-RS-T). DIAGNOSIS: MDS-RS is a lower risk MDS, with single or multilineage dysplasia (SLD/MLD), <5% bone marrow (BM) blasts and ≥15% BM RS (≥5% in the presence of SF3B1 mutations). MDS/MPN-RS-T, now a formal entity in the MDS/MPN overlap syndromes, has diagnostic features of MDS-RS-SLD, along with a platelet count ≥ 450 × 10(9)/L and large atypical megakaryocytes (similar to BCR-ABL1 negative MPN). MUTATIONS AND KARYOTYPE: Mutations in SF3B1 are seen in ≥80% of patients with MDS-RS-SLD and MDS/MPN-RS-T, and strongly correlate with the presence of BM RS; MDS/MPN-RS-T patients also demonstrate JAK2V617F, ASXL1, DNMT3A, SETBP1, and TET2 mutations; with ASXL1/SETBP1 mutations adversely impacting survival. Cytogenetic abnormalities are uncommon in both diseases. RISK STRATIFICATION: Most patients with MDS-RS-SLD are stratified into lower risk groups by the revised-International Prognostic Scoring System (R-IPSS). Disease outcome in MDS/MPN-RS-T is better than that of MDS-RS-SLD, but worse than that of essential thrombocythemia. Both diseases have a low risk of leukemic TREATMENT: Anemia and iron overload are complications seen in both and are managed similar to lower risk MDS and MPN. Aspirin therapy is reasonable in MDS/MPN-RS-T, especially in the presence of JAK2V617F, but the value of platelet-lowering drugs is uncertain.

Reclassifying myelodysplastic syndromes: what's where in the new WHO and why.

A revision to the 4th edition of the WHO Classification of myelodysplastic syndromes (MDSs), originally published in 2008, is expected in mid-2016. Based on recommendations of a Clinical Advisory Committee, the revision will aim to incorporate new discoveries in MDS that impact existing disease categories. Although the basic diagnostic principles of the WHO classification remain unchanged, several changes to the classification are proposed. All revisions are considered preliminary until the actual publication of the monograph and online document. Proposals for change include abandoning the routine use of "refractory anemia/cytopenia" in the various disease names, including the prognostic significance of gene mutations in MDS, revising the diagnostic criteria for MDS entities with ring sideroblasts based on the detection of SF3B1 mutations, modifying the cytogenetic criteria for MDS with isolated del(5q), reclassifying most cases of the erythroid/myeloid type of acute erythroleukemia, and recognizing the familial link in some cases of MDS. This review will provide details of the major proposed changes as well as rationale for the revisions.

Clinical and genetic characteristics of congenital sideroblastic anemia: comparison with myelodysplastic syndrome with ring sideroblast (MDS-RS).

Sideroblastic anemia is characterized by anemia with the emergence of ring sideroblasts in the bone marrow. There are two forms of sideroblastic anemia, i.e., congenital sideroblastic anemia (CSA) and acquired sideroblastic anemia. In order to clarify the pathophysiology of sideroblastic anemia, a nationwide survey consisting of clinical and molecular genetic analysis was performed in Japan. As of January 31, 2012, data of 137 cases of sideroblastic anemia, including 72 cases of myelodysplastic syndrome (MDS)-refractory cytopenia with multilineage dysplasia (RCMD), 47 cases of MDS-refractory anemia with ring sideroblasts (RARS), and 18 cases of CSA, have been collected. Hemoglobin and MCV level in CSA are significantly lower than those of MDS, whereas serum iron level in CSA is significantly higher than those of MDS. Of 14 CSA for which DNA was available for genetic analysis, 10 cases were diagnosed as X-linked sideroblastic anemia due to ALAS2 gene mutation. The mutation of SF3B1 gene, which was frequently mutated in MDS-RS, was not detected in CSA patients. Together with the difference of clinical data, it is suggested that genetic background, which is responsible for the development of CSA, is different from that of MDS-RS.

Occurrence of the JAK2 V617F mutation in the WHO provisional entity: myelodysplastic/myeloproliferative disease, unclassifiable-refractory anemia with ringed sideroblasts associated with marked thrombocytosis.

The JAK2/V617F mutation has been noted in essential thrombocytemia. We investigated 19 cases with refractory anemia with ringed sideroblasts (RARS), including three RARS with thrombocytosis (RARS-T). Only the RARS-T patients showed this mutation. More cases need to be analyzed to determine the prevalence of the JAK2/V617F mutation in RARS-T.

Congenital sideroblastic anemias.

Congenital forms of sideroblastic anemia constitute a subset of uncommon disorders within the wider spectrum of sideroblastic anemias, all of which are diagnosed by the presence of pathologic iron deposits in erythroblast mitochondria. The congenital sideroblastic anemias are heterogeneous disorders; some arise from known molecular defects but others are diagnosed only by their clinical features. Elucidation of several of the underlying defects has advanced our understanding of heme biosynthesis and iron metabolism in the erythroid cell. With the details of the porphyrin synthetic pathway clarified, now the important frontier of research is investigation of the mechanisms of mitochondrial and cellular iron homeostasis and their relationship to the regulation of heme biosynthesis. Knowledge gained from efforts in this area of study may also provide new approaches to treatments, which remain largely supportive for most types of congenital sideroblastic anemia.

[Sideroblastic anemias]. / Sideroblastische Anämien.

Sideroblastic anemias are a heterogenous group of disorders characterized by the presence of sideroblasts in the bone marrow aspirate. Current classification schemes distinguish between diseases of the heme synthesis pathway and diseases of other mitochondrial pathways which can either be of primary origin (defects in mitochondrial DNA) or of secondary origin (defects in nuclear DNA). Although several distinct hereditary forms exist, sideroblastic anemias are most frequently acquired diseases and belong to the group of myelodysplastic syndromes with the propensity to develop into overt leukemia. Treatment is mainly supportive (vitamins, blood transfusions, cytokines) and only rarely are bone marrow transplantations performed. The molecular defects of a few hereditary forms have already been elucidated, but the genes involved in the acquired forms are still largely unknown.

Classification and scoring systems in myelodysplastic syndromes: a retrospective analysis of 311 patients.

The main objective of this study was to evaluate the role of the recent World Health Organization (WHO) classification for assessing prognosis in patients with myelodysplastic syndromes (MDS). To this effect, we analyzed the prognostic impact of the WHO and French-American-British (FAB) morphologic classifications and of four different scoring systems in a series of 311 patients with primary MDS diagnosed between October 1990 and June 2001. Both the FAB and WHO classifications identified groups with different prognoses (p<0.0001), those presenting refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) showing the best prognosis. The WHO classification subdivided RA into RA with only red cell dysplasia, and refractory cytopenia with multilineage dysplasia (RCMD), and RARS into RARS plus refractory cytopenia with multilineage dysplasia and ringed sideroblast (RCMD-RS). In our population, we have shown that the two subtypes characterized by dysplasia affecting exclusively the erythroid population (RA and RARS) have a better prognosis, with a median survival of 122.2 and 81.9 months, respectively, than those with multilineage dysplasia (RCMD and RCMD-RS) with a median survival of 32.3 and 43.2 months, respectively. There were no significant differences in median survival comparing RA with RAS (p<0.95), or comparing RCMD with RSCMD (p<0.97). Besides, the four scoring systems discriminated our MDS patients in terms of survival, and an increase in prognostic capacity was achieved on adding the score to the morphological classifications. Risk scoring had a greater prognostic impact than the FAB and WHO classifications. Prognostic scoring systems may be an important tool for risk stratification in hematological practice, and add significance to morphological classification. Combined application of the WHO classification and score system is useful for improving the identification of patients with a poorer prognosis. The WHO classification establishes more homogeneous subcategories than the FAB classification and is also able to identify groups with different prognoses.

[Refractory anaemia with ringed sideroblasts (RARS) associated with marked thrombocytosis: a provisional entity in the WHO classification of haematological malignancies]. / Thrombocytose majeure et anémie réfractaire avec sidéroblastes en couronne: une entité provisoire dans la classification OMS des hémopathies.

The WHO classification describes a group of myelodysplastic/myeloproliferative diseases, including a provisional entity, refractory anaemia with ringed sideroblasts (RARS) associated with marked thrombocytosis, underlining that is a provisional entity without consensus of belonging to myelodysplastic rather than to myeloproliferative syndromes. The authors report two cases with features of refractory anaemia with excess of ringed sideroblasts and marked thrombocytosis. In the first case, RARS is concomitant with thrombocytosis and fits the WHO criteria for this temporary entity. The second case is a typical RARS, who developed a thrombocytosis after several years and emphasizes that a link, at least progressive, exists between RARS and myeloproliferative disorders. The authors summed up the various situations related to secondary or primary acquired sideroblastic anaemia, likewise to primitive and reactive thrombocytosis. The cases of RARS + marked thrombocytosis reported in the literature are few in number and do not allow to settle between a particular form of myelodysplastic syndrome and a myeloproliferative disorder, a fully justified reason to classify these patients in a temporary group. To date, there is no codified therapy for this disorders.

Ringed sideroblasts with thrombocytosis: an uncommon mixed myelodysplastic/myeloproliferative disease of older adults.

Sideroblastic anaemia with ringed sideroblasts and marked thrombocytosis, hereupon referred to as ringed sideroblasts with thrombocytosis (RST), is a provisional entity in the 2001 World Health Organisation classification scheme. This retrospective study identified 16 patients with RST over a 7-year period. Proposed diagnostic criteria include a sustained platelet count > 500 x 10(9)/l, > or = 15% ringed sideroblasts, < 3% bone marrow blasts, and normal conventional cytogenetics. The median age was 76 years with eight males and eight females. With a median follow-up of 41 months, RST patients had a median overall survival of 71 months, comparable with refractory anaemia having ringed sideroblasts, but less favourable than essential thrombocythaemia. Thus far, no patients with RST are known to have died of disease-related causes. Patients with ringed sideroblasts and/or thrombocytosis need to be carefully evaluated for a variety of haematological diseases that may confer significantly different prognoses.

Factors influencing survival in myelodysplastic syndromes in a Brazilian population: comparison of FAB and WHO classifications.

The WHO classification for myelodysplastic syndromes (MDS) has introduced new categories with prognostic relevance. Our aim was to examine the predictive value of the WHO and the FAB classification compared to parameters of peripheral blood, bone marrow and IPSS. Clinical data, peripheral blood counts, bone marrow (BM) cytology and histology and survival were analyzed in consecutive newly diagnosed adult patients with MDS. All cases were diagnosed according to FAB criteria and reclassified by the WHO proposal. Among 150 patients entering the study median age was 58 years (12-90). According to FAB, 90 patients had refractory anemia (RA), 18 sideroblastic anemia, 34 refractory anemia with excess of blasts (RAEB), three RAEB-t and five chronic myelomonocytic leukemia. Using the WHO proposal, one half of the patients with RA changed category. One patient had the 5q-syndrome. There were 25 cases with refractory cytopenias with multilineage dysplasia (RCMD) and 23 WHO "unclassified". These last patients presented few cell atypias, favorable IPSS and a good survival as has been described for refractory cytopenias in pediatric MDS. Hypocellular BM was found in 24% of the patients. Karyotype was available in only 85 cases. In the univariate analysis, both classifications, hemoglobin values, hypercellular bone marrow and IPSS had an influence on survival. Using the bootstrap resampling as stability test for the model created by the multivariate analysis, the WHO classification entered the model in 73%, FAB in 38% and IPSS in only 7%. Therefore, in a setting with a high number of low-risk MDS, the WHO classification is the best predictor of survival of the patients.

Ultrastructural features of bone marrow cells from patients with acquired sideroblastic anemia.

The ultrastructural findings of the bone marrow cells from 15 patients with acquired sideroblastic anemia are presented. The red cell precursors from all patients showed the presence of electron-dense material in the mitochondria, representing most probably iron deposits. A great number of these mitochondria were completely destroyed. The erythropoietic precursors from one of the patients showed markedly elongated mitochondria that measured up to 3 microm. In addition numerous cytoplasmic vacuoles were observed. The red cell precursors from 60% of the patients showed signs of dyserythropoiesis, such as incomplete nuclear division and nuclear distortion. The polymorphonuclears from 47% of the patients presented nuclear abnormalities expressed as nuclear bridges, appendices, and blebs. In addition, phagocytosis of red blood cells was observed. The results of the study underline the advantages of the transmission electron microscope examination in visualization of intricate alterations in hematopoietic cells that cannot be detected with a light microscope.

The genetics of inherited sideroblastic anemias.

The sideroblastic anemias are a heterogeneous group of acquired and inherited bone marrow disorders defined by the presence of pathologic iron deposits in erythroblast mitochondria. While the pathogenesis of almost all cases of acquired sideroblastic anemia is unknown, the molecular genetic basis for several of the inherited forms have now been described. Initially, mutations in ALAS2 in X-linked sideroblastic anemia (XLSA) focused attention on the heme biosynthetic pathway as a primary cause of sideroblastic anemia. However, the subsequent description of the genes involved in XLSA with ataxia, thiamine-responsive megaloblastic anemia, and Pearson marrow-pancreas syndrome have implicated other pathways, including mitochondrial oxidative phosphorylation, thiamine metabolism, and iron-sulfur cluster biosynthesis, as primary defects in sideroblastic anemias that may only secondarily impact heme metabolism.

Essential thrombocythemia with ringed sideroblasts: a heterogeneous spectrum of diseases, but not a distinct entity.

BACKGROUND AND OBJECTIVES: According to the recently published WHO-classification essential thrombocythemia with ringed sideroblasts (ET/RS) remains an ambiguous category which may be considered as myelodysplastic/myeloproliferative disease, unclassifiable. Because until now only case reports or very small series of patients have been described, a more systematically performed study is warranted. DESIGN AND METHODS: A retrospective evaluation was carried out on 38 patients with the diagnosis of ET/RS and more than 15 % ringed sideroblasts on smears. Simultaneously performed bone marrow biopsies, follow-up examinations and survival data were also available. RESULTS: Based on cytological features and particular bone marrow findings including immunohistochemistry three patterns could be determined. These were associated with different clinical features and in particular prognosis. Group I included six patients whose diagnosis was consistent with ET, group II comprised 21 patients revealing prefibrotic and early fibrotic chronic idiopathic myelofibrosis (CIMF) and finally 11 patients (group III) displayed myelodysplastic syndromes (MDS). Follow-up studies revealed that no patient with ET showed a fiber increase but eight CIMF patients developed overt myelofibrosis and four patients of the MDS group developed secondary acute myeloid leukemia. In comparison with a control group of 39 patients with true ET, prognosis was significantly different because our cohort showed a median survival of 100 months that contrasted significantly with the 170 months in the patients with true ET. INTERPRETATION AND CONCLUSIONS: Ringed sideroblasts are not a pathognomonic feature of MDS, but may indicate a dysplasia probably associated with a primary or secondary disturbance of iron metabolism in a variety of disorders. For this reason, a more accurate classification of so-called ET/RS patients is warranted by evaluation of smears and in particular bone marrow biopsy specimens. According to our findings these patients should be classified as having either ET, CIMF or MDS and show a significantly different survival pattern.

Two types of acquired idiopathic sideroblastic anaemia (AISA): a time-tested distinction.

In 1982, acquired idiopathic sideroblastic anaemia (AISA) was included by the French-American-British (FAB) Co-operative Group in their classification of myelodysplastic syndromes (MDS). However, the malignant potentiality of AISA has always been a matter of debate. In different series, median survival and rates of transformation into acute myeloid leukaemia (AML) varied extensively. On cytomorphological grounds, AISA can be divided into pure (dyserythropoietic) sideroblastic anaemia (PSA), in which dysplasia is confined to erythropoietic cells, and a true myelodysplastic form (RARS), which is characterized by additional dysplastic features of granulopoiesis and/or megakaryopoiesis. In a previous study, based on retrospective analysis of 94 patients with AISA, we found that both types of sideroblastic anaemia differed considerably in terms of survival and risk of AML transformation. Almost identical results have now been obtained through a prospective study of 232 new patients with AISA. The difference in survival between PSA and RARS remained significant over the whole period of follow-up (survival after 3 years being 77% vs. 56%; P = 0.003), and the incidence of AML did not increase with time in the PSA group, even in the long term. This prospective study strongly supported our conclusion that cytomorphological distinction between PSA and RARS provides valuable prognostic information.