Idiopathic sideroblastic anemia: presence of sideroblastic changes in the erythropoietic precursors cultured from peripheral blood.

Peripheral blood mononuclear cells from five patients with idiopathic sideroblastic anemia were examined in clonal culture for circulating erythropoietic precursors. Three of these patients had relatively mild anemia and revealed significant burst formation. Two patients who had severe anemia and required regular blood transfusions showed severe diminution or absence of circulating precursors. These results could suggest that the number of circulating erythropoietic precursors reflects effective erythropoiesis in the marrow. Ultrastructural morphology and ultrastructural Prussian-blue staining of the bursts from a patient revealed the characteristic mitochondrial deposition of ferrugionous material in pathologic normoblasts. Peripheral blood clonal cell cultures would, therefore, appear to be a potentially useful tool for analysis of biochemical abnormalities in idiopathic sideroblastic anemia.     

Abnormalities of flavin monooxygenase as an etiology for sideroblastic anemia

We postulated that a deficiency of flavin monooxygenase (FMO)-a ferrireductase component of cells-could produce sideroblastic anemia. FMO is an intracellular ferrireductase which may be responsible for the obligatory reduction of ferric to ferrous iron so that reduced iron can be incorporated into heme by ferrochelatase. Abnormalities of this mechanism could result in accumulation of excess ferric iron in mitochondria of erythroid cells to produce ringed sideroblasts and impair hemoglobin synthesis. To investigate this hypothesis we obtained blood from patients with sideroblastic anemia and normal subjects. Extracts of peripheral blood lymphocytes were used to measure ferrireduction by utilization of NADPH. Lymphoid precursors are reported to accumulate iron in mitochondria similarly to erythroid precursors. Utilization of lymphoid precursors avoided the need for bone marrow aspirations. We studied three patients with sideroblastic anemia. One patient and his asymptomatic daughter had a significant decrease in ferrireductase activity. They also had markedly diminished concentrations of FMO in lymphocyte protein extracts on Western blots. This was accompanied by increased concentration of mobilferrin in the extracts. These results suggest that abnormalities of FMO and mobilferrin may cause sideroblastic anemia and erythropoietic hemochromatosis in some patients.     

The Contributions of Erythropoietic and Nonerythropoietic Haem Turnover to the Early Labelled Peak of Endogenous CO Formation in Man

The endogenous production of ¹⁴CO during the first week after administration of glycine-2-¹⁴C (early labelled peak, ELP) was determined in 13 healthy subjects. The subjects were studied during normal, suppressed or stimulated erythropoiesis induced by hypertransfusion and phlebotomy, respectively. The production of ¹⁴CO was calculated from determinations of the specific activity of the body CO store and the endogenous production of CO. The incorporation of labelled glycine into circulating red cell haemoglobin haem was calculated from the maximal specific activity of haemoglobin haem and the total amount of Hb. The average ELP was 73.0 × 10³ disintegrations per min (dpm) and the incorporation of glycine into circulating haemoglobin haem 491 × 10³ dpm in controls. The ELP and the incorporation of glycine increased by 86% and 92%, respectively, in phlebotomized subjects and decreased by 37% and 62%, respectively, in hypertransfused subjects. A linear regression equation was calculated for the relationship between ELP and erythropoiesis, expressed as the incorporation of glycine into circulating haemoglobin haem. The residual ELP remaining in the absence of erythropoiesis was 24.9 × 10³ dpm calculated from data of all the subjects, and 32.8 × 10³ dpm calculated from data of controls and hypertransfused subjects only. In conclusion, erythropoietic haem turnover was found to contribute about 60% and nonerythropoietic (mainly hepatic) haem turnover about 40% of the ELP in man.     

Iron overload complicating sideroblastic anemia--is the gene for hemochromatosis responsible?

Idiopathic hemochromatosis is a hereditary disease that is associated with human leucocytic antigens A3, B7, and B14. A genetic association between human leucocytic antigen-linked hemochromatosis and idiopathic refractory sideroblastic anemia has been suggested that may predispose some patients with idiopathic refractory sideroblastic anemia to develop gross iron overload. Study of the family of a patient with idiopathic refractory sideroblastic anemia and hemochromatosis revealed that 2 of 5 first-degree relatives had significant elevations of serum ferritin, and a shared human leucocytic antigen haplotype, supporting the concept that patients with idiopathic refractory sideroblastic anemia and significant iron overload have at least one allele for hemochromatosis.     

Three kinships with ALAS2 P520L (c. 1559 C --> T) mutation, two in association with severe iron overload, and one with sideroblastic anemia and severe iron overload

Mutations in aminolevulinate synthase 2 (ALAS2) are usually associated with sideroblastic anemia and iron overload. The objective of this study was to determine if "mild" mutations in ALAS2 might increase the severity of primary iron overload. Direct sequencing of the ALAS2 gene was performed on 24 subjects with primary hemochromatosis and one subject with sideroblastic anemia with severe iron overload. We identified a novel mutation P520L (c. 1559 C --> T) in ALAS2 in three subjects. Two had severe iron overload and no anemia: one also had HFE C282Y homozygosity, and the other was wildtype for HFE and other iron-related genes. The third subject had sideroblastic anemia with iron overload, and was hemizygous for both P520L and R560H (c. 1679 G --> A) mutations in ALAS2. The P520L mutation was found at a frequency of 0.0013 (741 alleles) in white control subjects, but was not found in 158 alleles from black control subjects. The proline in this position is highly conserved across species from humans to zebrafish. However, genotype/phenotype studies of the families demonstrate that the P520L mutation alone has no iron-associated phenotype, but it may act as a modifier of iron overload in the presence of mutations in HFE or other uncharacterized hemochromatosis genes. Thus, ALAS2 mutations might contribute to more severe iron loading in persons with primary hemochromatosis.     

Pathophysiological classification of acquired bone marrow failure based on quantitative assessment of erythroid function

Bone marrow failure encompasses a broad spectrum of disorders including aplastic, dysmyelopoietic and myelophtisic anemias. In the present study, these anemias were characterized according to the degree of erythroid proliferation and efficiency of erythropoiesis. Total erythropoietic activity was evaluated in 43 patients by measuring the erythron transferrin uptake (ETU). It averaged 20% of basal (range 3-43%) in 13 patients with severe aplastic anemia, 75% of basal (range 60-103%) in 3 patients with extensive bone marrow infiltration by neoplastic cells, 131% of basal (range 50-217%) in 16 patients with refractory anemia, and 452% of basal (range 63-720) in 11 patients with idiopathic refractory siderobastic anemia. Respective efficiencies of erythropoiesis were 74% in aplastic anemia, 70% with bone marrow infiltration, 46% in refractory anemia, and 14% in sideroblastic anemia. Based on the ETU, patients could be categorized into absolute marrow failure, relative marrow failure, and adequate erythropoietic response to anemia. This simple determination of proliferating activity of the erythroid marrow can provide useful information on the pathophysiology of marrow failure and a basis for the selection of therapeutic approaches.     

Iron-Laden Mitochondria in Reticulum Cells of Hypersiderotic Human Bone Marrows

Iron-laden mitochondria were observed in three cases of primary nonhereditary sideroblastic anemia. The cells involved are considered to be a peculiartype of reticulum cell, possibly with erythropoietic potentiality. This featureand the rare presence of iron in mitochondria of reticulum cells which areclearly identifiable as macrophages suggest that an enzymatic defect in hemoglobin synthesis may account for the majority, but probably not all instances, ofiron-laden mitochondria.

Submitted on May 3, 1966 Accepted on January 9, 1967     

Sideroblastic anemia terminating in myelofibrosis

Two patients with primary acquired sideroblastic anemia who eventually developed myelofibrosis with myeloid metaplasia are reported. Splenectomy was performed in one patient because of increasing blood transfusion requirements, and splenic histology revealed both myeloid metaplasia and ringed sideroblasts. The second patient showed a partial response of the sideroblastic anemia to pyridoxine therapy during the early stages of development of the myelofibrosis. Myelofibrosis with myeloid metaplasia may represent a nonspecific response of the marrow tissue to sideroblastic anemia as to other primary hematologic disorders.     

Combined phenotypic and genotypic analysis of ringed sideroblasts in acquired idiopathic sideroblastic anemia

Bone marrow from an 81-year-old male with acquired idiopathic sideroblastic anemia was found to be mosaic for 45,X/46,XY cell lines. Analysis of ringed sideroblasts for the presence or absence of a quinicrine fluorescent Y body indicated that all sideroblastic cells had lost the Y chromosome. The demonstration that the ringed sideroblasts were cytogenetically abnormal in this patient provides evidence that the cytogenetic changes often found in patients with sideroblastic anemia may not be due to randomly acquired chromosome aberrations accompanying tissue aging unrelated to the disease process.     

Nonmyeloablative allogeneic hematopoietic stem cell transplantation for congenital sideroblastic anemia

Congenital sideroblastic anemia (CSA) is a dyserythropoietic disorder that leads to transfusion dependency and subsequent iron overload. Nonmyeloablative allogeneic hematopoietic stem cell transplantation (NST) was performed for a patient with CSA, who had contraindications to conventional allografting. Conditioning was fludarabine, low-dose total body irradiation and antithymocyte globulin, followed by peripheral blood stem cell transplant. Cyclosporine and mycophenolate mofetil were used for graft-versus-host disease prophylaxis. Complete donor chimerism was observed day +131. Early after transplant, the patient became transfusion independent, allowing a regular phlebotomy program. On day +190, refractory lactic acidosis followed by fatal cardiovascular collapse developed, without evidence of infection. Data from this case demonstrates that NST may correct the erythropoietic defect of CSA.     

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.     

Refractory sideroblastic anemia secondary to autoimmune hemolytic anemia.

A 75-year-old woman was hospitalized with autoimmune hemolytic anemia. During a period of 22 months the patient had six hemolytic crises which responded to treatment with prednisone and azathioprine. During the last admission the patient presented a sideroblastic anemia with 98% of 'ring sideroblasts' in the bone marrow. This association has never, to our knowledge, been reported before. It is possible that the immunosuppression played a definite role in the development of this sideroblastic anemia.     

Abnormal Iron Incorporation, Survival, Protoporphyrin Content and Fluorescence of One Red Cell Population in Preleukemic Sideroblastic Anemia

The dimorphic blood picture in sideroblastic anemia suggests the coexistence of at least two types oferythrocyte, the populations with thesmaller RBCs being responsible forthe crucial abnormality, namely theimpairment of iron incorporation intoprotoporphyrin. In a patient with sideroblastic anemia who subsequently developed acute myelocytic leukemia,we found a light and a heavy cellpopulation to be morphologically different, the lighter cells showing asmaller MCV and lower MCH, a higherreticulocyte count, fluorocyte countand protoporphyrin content. Radioironuptake and ⁵¹Cr survival were 3.5%and 8.2 days for the lighter fraction,37% and 20 days for the heavier fraction. Thus, the impairment of ironincorporation, the high erythrocyteprotoporphyrin content, and the reduced survival of red cells in thispatient with sideroblastic anemia appeared to be largely confined to thered cell population with the smallerRBCs.

Submitted on December 14, 1971 Revised on May 5, 1972 Accepted on May 8, 1972     

An infant case of sideroblastic anemia that responded to oral pyridoxine]

An 8-month-old boy was admitted because of paleness. Laboratory studies disclosed microcytic and hypochromic anemia: red blood cell count 156 x 10(4)/microliter, hemoglobin 3.5 g/dl, mean cell volume 66 fl, and reticulocytes 0.5/1000. Serum iron was 433 micrograms/dl and exocrine pancreatic dysfunction was not observed. Examination of bone marrow revealed prominent erythroid hyperplasia; 18% of the erythroblasts were distinct ringed sideroblasts. Electron microscopic studies found intramitochondrial iron deposits in the erythroblasts. The patient was given a diagnosis of sideroblastic anemia and responded to oral pyridoxine (50 mg/day) with an immediate increase of reticulocytes to 97/1000, resulting in an improved hemoglobin concentration. He has maintained remission for more than 1 year following discontinuation of pyridoxine, which was administered for 2 months. Congenital sideroblastic anemia is relatively rare and mostly occurs in males, suggesting an X-linked recessive mode of inheritance. Recently, X-linked sideroblastic anemia has been shown to be caused by missense mutations in the delta-aminolevulinic acid synthase (ALAS) gene. A point mutation in exon 5 of the ALAS gene was found in this patient. Iron-deficiency anemia is the most common hematologic disease of infancy and childhood, resulting from lack of sufficient iron for synthesis of hemoglobin. It is therefore mandatory to differentiate sideroblastic anemia from iron-deficiency anemia and other common anemias.     

Evaluation of erythrocyte basic ferritin in the diagnosis of anemia

Erythrocyte basic ferritin (EF) concentration was determined in 64 normal subjects, 123 patients with anemia and 12 patients with leukopenia and thrombocytopenia. There was a significant difference between males and females. Other iron indices, including plasma iron (PI), total iron binding capacity (TIBC), zinc protoporphyrin (ZnPP) and plasma ferritin (PF) were also determined in all the subjects and bone marrow iron stain was determined in the 135 patients. The lowest EF concentration was seen in patients with iron deficiency anemia, being significantly lower than that in normal subjects. EF concentration in patients with iron deficiency erythropoiesis was also lower than that in normal subjects and at the same time significantly different from that in patients with iron deficiency anemia. EF concentration increased prior to PF concentration in patients with iron deficiency anemia who had been treated for a period of 1-8 weeks. EF concentration in patients with anemia of chronic diseases had a significant difference as compared with that in normal subjects and in patients with iron deficiency anemia, but EF concentration in those patients who were accompanied by iron deficiency was similar to that in patients with simple iron deficiency anemia. EF concentration in some iron overloaded patients (aplastic anemia, megaloblastic anemia, MDS etc.) was significantly higher than that in normal subjects. It was demonstrated that there was a good correlation between EF concentration and bone marrow sideroblastic iron in the rank correlation analysis of the iron indices in 135 patients (rs 0.893, P less than 0.01). PF concentration had the best correlation with marrow iron (rs 0.948, P less than 0.01).     

Responsiveness of bone marrow erythropoietic stem cells (CFU-E and BFU-E) to recombinant human erythropoietin (rh-Ep) in vitro in aplastic anemia and myelodysplastic syndrome

Responsiveness of bone marrow erythropoietic stem cells (CFU-E and BFU-E) to recombinant human erythropoietin (rh-Ep) was examined in vitro in 23 patients with aplastic anemia and 14 with myelodysplastic syndrome (MDS) to investigate the clinical use of rh-Ep for these diseases. Bone marrow mononuclear cells were cultured by methylcellulose methods for CFU-E and BFU-E assays. In normals, the CFU-E numbers reached a plateau of increase at Ep doses of almost 2-5 units, and no further increase was observed with the addition of larger Ep doses. In aplastic anemia, the responses of CFU-E to Ep were relatively good in nonsevere type and generally poor in severe type. However, the CFU-E numbers increased with increasing doses of Ep in some of the patients with aplastic anemia. Among the patients with MDS, the responses of CFU-E to Ep were relatively good in primary acquired refractory anemia (PARA) and primary acquired sideroblastic anemia. On the other hand, the responses of CFU-E to Ep were poor in refractory anemia with an excess of blasts (RAEB) and RAEB in transformation among the MDS patients. BFU-E responses to Ep were poor in severe aplastic anemia, RAEB, and RAEB-T. However, there are Ep responsive patients in some of aplastic anemia and PARA. High titers of rh-Ep were suggested to be effective clinically in some patients with aplastic anemia and those with PARA.     

Sideroblastic anemia with splenic abscess and fatal thromboemboli after splenectomy.

A man with sideroblastic anemia had a splenectomy because of a salmonella abscess of the spleen that had ruptured into the colon. Two months later he developed recurrent thrombophiebitis and fatal thromboembolism associated with thrombocytosis. A review of the literature showed multiple additional cases of sideroblastic anemia with thrombocytosis and thromboembolism after splenectomy. In many of these cases the patient died. Splenectomy for treatment of a sideroblastic anemia probable is contraindicated. If splenectomy is done, long-term therapy to avoid thromboembolic complications probably should be maintained for many months or even years.     

A new chromosome abnormality in idiopathic sideroblastic anemia: 46, XY,del11q23

A new marker chromosome, deletion 11q23, was observed with the Giemsa banding technique in the bone marrow of a patient with idiopathic sideroblastic anemia. The abnormality was not detectable in the peripheral blood or with nonbanded chromosome studies. Nineteen of 40 cases of this disorder studied and reported to date had chromosomal aberrations, although the majority had only nonbanded karyotypes performed. This apparently high incidence of chromosomal defects and the finding in the present case indicate that more banded-karyotype analyses are needed to assess the presence of possible nonrandom cytogenetic changes in idiopathic sideroblastic anemia.     

Primary acquired sideroblastic anemia, thrombocytosis, and trisomy 8

 Myelodysplastic syndromes are usually associated with pancytopenia. Disorders involving deletion of the long arm of chromosome 5 (5q- syndrome) and, rarely, patients with karyotypic abnormalities involving chromosome 3 associated with abnormal thrombopoiesis may have a normal or even raised platelet count. Other cytogenetic abnormalities in myelodysplasia are invariably associated with cytopenia in one or all cell lineages. We report a patient who initially presented with slight anemia and a raised platelet count. Further investigations suggested a diagnosis of primary acquired sideroblastic anemia. Cytogenetic examination revealed a clone with trisomy 8. We believe this is the first reported case of trisomy 8 with trilineage myelodysplasia and thrombocytosis with primary acquired sideroblastic anemia. Received: 13 August 1996 /Accepted: 12 December 1996