Iron-loading anemia. Treatment with repeated phlebotomies and pyridoxine

The effect of iron overload and chelation on erythroid differentiation

We investigated the mechanisms of hematopoietic disorders caused by iron overload and chelation, in particular, the inhibition of erythroblast differentiation. Murine c-kit(+) progenitor cells or human CD34(+) peripheral blood hematopoietic progenitors were differentiated in vitro to the erythroid lineage with free iron and/or an iron chelator. Under iron overload, formation of erythroid burst-forming unit colonies and differentiation to mature erythroblasts were significantly suppressed; these effects were canceled by iron chelation with deferoxamine (DFO). Moreover, excessive iron burden promoted apoptosis in immature erythroblasts by elevating intracellular reactive oxygen species (ROS). Interestingly, both DFO and a potent anti-oxidant agent reduced intracellular ROS levels and suppressed apoptosis, thus restoring differentiation to mature erythroblasts. Accordingly, intracellular ROS may represent a new therapeutic target in the treatment of iron overload.

X-linked sideroblastic anaemia with ataxia: another mitochondrial disease?

OBJECTIVES

The syndrome of X-linked sideroblastic anaemia with ataxia is rare, described only twice in the literature. The aim was to obtain clinical neurological and haematological data about this rare syndrome throughout adult life.

METHODS

A family is described with two affected brothers and two affected maternal uncles. The family was evaluated clinically. Haematological investigations included full blood count, blood film, iron studies, free erythrocyte protoporphyrin (FEP) concentrations and a bone marrow examination where possible.

RESULTS

Core neurological features included motor delay, ataxia evident from early childhood, and dysarthria. Neurological features were non-progressive until the fifth decade when slow progression became evident. Some family members showed mild spasticity. Patients usually have a mild asymptomatic anaemia or a borderline decreased mean corpuscular volume. Blood film examination showed Pappenheimer bodies. Bone marrow examination showed ring sideroblasts, indicating raised erythrocyte iron. Free erythrocyte protoporphyrin (FEP) concentrations were raised.

CONCLUSIONS

Haematological features are subtle and can be easily overlooked, and individual patients may not display all the abnormal features. X-linked ataxias are rare and incorrect genetic advice may be given if the diagnostic haematological features of X-linked sideroblastic anaemia are overlooked. Males with early onset ataxia should have a haematological evaluation including a blood film, with a bone marrow examination if abnormal blood count indices and measurement of FEP concentrations raise suspicion. The condition has parallels with Pearson's syndrome and Friedreich's ataxia. All three conditions are associated with mitochondrial iron handling defects and ataxia. The human ATP binding cassette gene (hABC7) is a candidate gene and requires further investigation.

Four New Mutations in the Erythroid-Specific 5-Aminolevulinate Synthase (ALAS2) Gene Causing X-Linked Sideroblastic Anemia: Increased Pyridoxine Responsiveness After Removal of Iron Overload by Phlebotomy and Coinheritance of Hereditary Hemochromatosis

X-linked sideroblastic anemia (XLSA) in four unrelated male probands was caused by missense mutations in the erythroid-specific 5-aminolevulinate synthase gene (ALAS2). All were new mutations: T647C, C1283T, G1395A, and C1406T predicting amino acid substitutions Y199H, R411C, R448Q, and R452C. All probands were clinically pyridoxine-responsive. The mutation Y199H was shown to be the first de novo XLSA mutation and occurred in a gamete of the proband’s maternal grandfather. There was a significantly higher frequency of coinheritance of the hereditary hemochromatosis (HH)HFE mutant allele C282Y in 18 unrelated XLSA hemizygotes than found in the normal population, indicating a role for coinheritance ofHFE alleles in the expression of this disorder. One proband (Y199H) with severe and early iron loading coinherited HH as a C282Y homozygote. The clinical and hematologic histories of two XLSA probands suggest that iron overload suppresses pyridoxine responsiveness. Notably, reversal of the iron overload in the Y199H proband by phlebotomy resulted in higher hemoglobin concentrations during pyridoxine supplementation. The proband with the R452C mutation was symptom-free on occasional phlebotomy and daily pyridoxine. These studies indicate the value of combined phlebotomy and pyridoxine supplementation in the management of XLSA probands in order to prevent a downward spiral of iron toxicity and refractory anemia.

Four New Mutations in the Erythroid-Specific 5-Aminolevulinate Synthase (ALAS2) Gene Causing X-Linked Sideroblastic Anemia: Increased Pyridoxine Responsiveness After Removal of Iron Overload by Phlebotomy and Coinheritance of Hereditary Hemochromatosis

X-linked sideroblastic anemia (XLSA) in four unrelated male probands was caused by missense mutations in the erythroid-specific 5-aminolevulinate synthase gene (ALAS2). All were new mutations: T647C, C1283T, G1395A, and C1406T predicting amino acid substitutions Y199H, R411C, R448Q, and R452C. All probands were clinically pyridoxine-responsive. The mutation Y199H was shown to be the first de novo XLSA mutation and occurred in a gamete of the proband’s maternal grandfather. There was a significantly higher frequency of coinheritance of the hereditary hemochromatosis (HH)HFE mutant allele C282Y in 18 unrelated XLSA hemizygotes than found in the normal population, indicating a role for coinheritance ofHFE alleles in the expression of this disorder. One proband (Y199H) with severe and early iron loading coinherited HH as a C282Y homozygote. The clinical and hematologic histories of two XLSA probands suggest that iron overload suppresses pyridoxine responsiveness. Notably, reversal of the iron overload in the Y199H proband by phlebotomy resulted in higher hemoglobin concentrations during pyridoxine supplementation. The proband with the R452C mutation was symptom-free on occasional phlebotomy and daily pyridoxine. These studies indicate the value of combined phlebotomy and pyridoxine supplementation in the management of XLSA probands in order to prevent a downward spiral of iron toxicity and refractory anemia.

Treatment of erythropoietin-resistant anaemia with desferrioxamine in patients on haemofiltration

We studied 5 anaemic patients with Hb 74 +/- 8 g/l on haemofiltration (HF) treatment. They were iron overloaded. Their serum ferritin was 2667 +/- 8 micrograms/l. All patients' haemoglobin (Hb) levels decreased after an initial response to recombinant human erythropoietin (r-HuEPO) treatment. An increase in r-HuEPO dose from 100 to 400 U/kg s.c. thrice weekly with addition of oral and intravenous iron treatment for 8 weeks arrested the fall in Hb level. However, there was no significant increase in Hb during these 8 weeks. Iron was withdrawn at week 24 and desferrioxamine (DFO) treatment (i.v. doses of 2 g thrice weekly) was added to r-HuEPO from week 26 to 36. Two weeks after DFO initiation the Hb level increased to 110 g/l. Thereafter the r-HuEPO doses were reduced from 400 to 25 U/kg within 3 months. The Hb remained stable at a level of 110 g/l during the study, i.e., 17 months after the DFO treatment. Serum ferritin levels fell at a more rapid pace during DFO treatment and continued to decrease after DFO cessation for the following 17 months. In accordance with previous observations we found a positive effect of DFO treatment on erythropoiesis in patients with anaemia and iron overload. DFO treatment should be considered in patients with iron overload and r-HuEPO-resistant anaemia.

Sideroblastic anaemia

The startling morphological abnormalities of sideroblastic anaemia contrasts our uncertainty about its cause. Studies are hampered by the fact that the abnormality resides in the dividing and differentiating erythroblast which is difficult to obtain pure and in large numbers, and in which many levels of metabolic control must coexist. Recent molecular biology approaches have confirmed abnormalities of erythroid delta-aminolaevulinic acid synthase as the cause of X-linked, pyridoxine-responsive sideroblastic anaemia and mitochondrial DNA deletions as the most common cause of congenital macrocytic sideroblastic anaemia. They have also identified a second X-linked sideroblastic anaemia locus linked to phosphoglycerate kinase and associated with ataxia. An association between sideroblastic anaemia and the use of an oral copper chelating agent has highlighted unexplained links between erythroid copper and iron metabolism. Management decisions in relation to pyridoxine treatment, iron reduction, family studies, genetic counselling and antenatal diagnosis have in recent years become of practical relevance to families with known cases of congenital sideroblastic anaemia and careful documentation of the clinical outcome of these cases and of other family members is invaluable. Parallel and integrated studies on the molecular biology of erythroid differentiation are revealing the range of possible controlling influences on erythroblasts and defining the circumstances for each, allowing studies on the cause of the most prevalent form of sideroblastic anaemia (the idiopathic acquired form) and those inherited forms that are not X-linked to be approached with a much clearer perspective.

Improvement of sickle cell anemia by iron-limited erythropoiesis

We report the hematologic and clinical features of four adult patients (Pts.) with sickle cell anemia and iron-limited erythropoiesis. Two of the Pts. had spontaneous iron deficiency (chronic GI bleeding, low-grade hemoglobinuria). In the other two Pts. iron restriction was induced by periodic RBC aphereses as part of a pilot protocol designed to decrease intracellular HbS polymerization by MCHC reduction. Iron-limited erythropoiesis was defined by reduction in red cell indices (MCV range 60.4-67 fl) in the presence of low serum ferritin (range < 10-20 ng/ml). In these Pts. iron restriction did not cause clinically significant worsening of the anemia (Hb 7.8-9.0 g/dl). In two Pts. the anemia actually improved. Other hematologic effects of iron restriction were: decreased MCHC, reticulocyte count, RDW, and dense cells. A reduced hemolytic rate was suggested by a lowering of serum bilirubin and LDH. In one of the Pts. the 51Cr RBC T1/2 survival increased from 12 to 16 days. The intracellular HbS polymer fractions (fp) were determined at 25% O2 by Csat and with the use of the conservation of mass equation. The baseline fp values ranged from 0.48-0.53. After iron restriction they ranged from 0.33-0.48. The fp decreased even though iron-limited erythropoiesis also lowered the Hb F concentration in three of our Pts. In one of the two Pts. with induced iron depletion, hospitalization days for pain crises decreased from an average of 4.5 days/month (2 year baseline period) to an average of 0.5 days/month in the 3 year follow-up after iron depletion. The second patient with induced iron restriction experienced the rapid healing of a leg ulcer. Controlled iron restriction should be explored as a therapeutic strategy in selected SS patients.

Microcytic anemia. Differential diagnosis and management of iron deficiency anemia

Microcytic anemia is defined as the presence of small, often hypochromic, red blood cells in a peripheral blood smear and is usually characterized by a low MCV (less than 83 micron 3). Iron deficiency is the most common cause of microcytic anemia. The absence of iron stores in the bone marrow remains the most definitive test for differentiating iron deficiency from the other microcytic states, ie, anemia of chronic disease, thalassemia, and sideroblastic anemia. However, measurement of serum ferritin, iron concentration, transferrin saturation and iron-binding capacity, and, more recently, serum transferrin receptors may obviate proceeding to bone marrow evaluation. The human body maintains iron homeostasis by recycling the majority of its stores. Disruptions in this balance are commonly seen during menstruation, pregnancy, and gastrointestinal bleeding. Although the iron-absorptive capacity is able to increase upon feedback regarding total body iron stores or erythropoietic activity, this physiologic response is minimal. Significant iron loss requires replacement with iron supplements. The vast majority of patients respond effectively to inexpensive and usually well-tolerated oral iron preparations. In the rare circumstances of malabsorption, losses exceeding maximal oral replacement, or true intolerance, parenteral iron dextran is effective. In either form of treatment, it is necessary to replete iron stores in addition to correcting the anemia.

Hereditary sideroblastic anemia with associated platelet abnormalities

A 62 year old male (R.H.) presented with a mild anemia (Hb 11-12 gm%) and a history of multiple hemorrhagic episodes. The marrow had 40-50% sideroblasts. Marrow chromosomes were normal. His wife was hematologically normal, while one daughter, age 30 years, had a sideroblastic anemia (Hb 11-12 gm%) with 40-50% sideroblasts in the marrow. Her anemia was first noted at age 15 years. Administration of vitamin B6 did not correct the anemia in either the father or daughter. Platelet abnormalities inherited jointly with this disorder are described for the first time. Both R.H. and his daughter had prolonged bleeding times, with normal PTT, PT times, fVIII:C, fVIII:Ag levels, and vWF multimers, which may rule out a von Willebrand's disease. They have normal platelet numbers but abnormally low platelet adhesiveness and greatly depressed ADP, collagen, and epinephrine responsiveness. Response to ristocetin was in the low normal range, and aggregation with thrombin was normal. While desmopressin completely normalized R.H.'s bleeding time, none of these platelet parameters were improved. No differences in the SDS PAGE protein patterns of RH platelets could be detected in comparison to normal samples. His platelets took up and released serotonin (5HT) normally, and electron micrographs defined no morphological abnormalities. However, no ATP was released from platelets activated with collagen, and when followed by thrombin about fourfold greater ATP was released by control platelets as compared to RH platelets. The dense granule fraction derived from RH platelets contained about 20% the level of ATP, 40% the level of ADP, and 50% the level of 5HT detected in a normal sample. The results indicate that the bleeding disorder is related to a non-classical heritable storage pool defect. The connection between the inherited sideroblastic anemia and platelet defects is obscure.

Hereditary sideroblastic anaemia and ataxia: an X linked recessive disorder

We report two families in which a non-progressive spinocerebellar syndrome and a sideroblastic anaemia are segregating together in an X linked recessive fashion. Four males in two generations of one family and a fifth male from an unrelated family had both conditions. Both the sideroblastic anaemia and the spinocerebellar syndrome differ from those which have previously been reported to be inherited in an X linked recessive manner. The association of these two clinically distinct disorders in two unrelated families suggests that they are either two closely linked loci which have undergone simultaneous mutation or pleiotropic effects of an altered allele at a single locus. All the heterozygous women had normal neurological examinations and normal haematocrits and red cell indices. Some had ring sideroblasts on bone marrow examination, a dimorphic peripheral blood smear, and raised serum free erythrocyte protoporphyrin, suggesting that a proportion of heterozygotes can be detected by appropriate haematological studies.

Severe iron deficiency causing loss of ring sideroblasts

A patient with primary sideroblastic anaemia was observed for more than 10 years with 50% ring sideroblasts in the bone marrow and a Hb of 84-109 g/l. Iron deficiency then developed with loss of stainable iron in marrow particles (reticuloendothelial iron) and loss of all ring sideroblasts. When iron tablets had brought the iron stores in the bone marrow up to subnormal levels, the Hb was over 110 g/l, somewhat higher than it had been when the iron stores were increased. The ring sideroblasts were again raised to more than 50%.

Factors affecting iron balance

The availability of radioisotopes of iron led to the performance of physiologic studies of the absorption, excretion, and kinetics of iron. The effects of dietary constituents and intestinal secretions upon iron absorption have been thoroughly explored and have permitted the development of tools for nutritional studies in various geographic areas of the world. The basic mechanisms for regulation of iron absorption are not fully understood. However, the isolation and characterization of newer iron-binding proteins, the existence of mucosal receptors in which there is competition for iron-binding sites with other metals, and the identification of a number of animal models with genetic abnormalities of iron absorption provide promise for development in the foreseeable future. The means by which the body informs the intestine to increase or decrease iron absorption is poorly understood, and the abnormality in hemochromatosis and iron overloading disorders remains unexplained. Much has been learned in recent years regarding the structure of iron-containing proteins and the variations that exist in different species. Similar problems remain to be solved with regard to the intermediary metabolism of iron in red blood cell precursors and other cells in the body. It is postulated that the combined usage of physiologic, biochemical, and immunologic investigations will provide the basic information required.

Iron overload in congenital erythrocyte pyruvate kinase deficiency

Severe iron overload developed in two patients with congenital erythrocyte pyruvate kinase deficiency. In one of them this was complicated by hepatic cirrhosis and endocrine dysfunction. In both patients, the institution of intermittent subcutaneous administration of desferrioxamine resulted in significant urinary iron excretion and a reduction in the degree of iron overload.

Leukemia in patients with acquired idiopathic sideroblastic anemia: an evaluation of prognostic indicators

The initial clinical and laboratory data of 25 patients with acquired idiopathic sideroblastic anemia (AISA) were analyzed. Criteria for accepting the diagnosis were hyperferremia, ringed marrow sideroblasts, ineffective erythropoiesis, and exclusion of associated hematologic disorders. The findings of a mean age at onset of 70 years, increased mean corpuscular volume, relative neutropenia; and occasional splenomegaly at diagnosis corresponded with previous reports. During the followup for a median period of 32 months, 6 patients (25%) transformed to acute myelogenous or myelomonocytic leukemia after widely variable intervals. The initial data base of these patients was compared to that of the remaining 19 patients in order to isolate predictive features. Only a lesser degree of hyperferremia (P less than 0.001) made the group going on to leukemia distinctive. The median survival of these patients was 20 months. The median survival of 19 patients not developing leukemia was 72 months for males and 42 months for females. Hemochromatosis was diagnosed in four patients and was a primary or associated cause of death in three. Analysis of the transfusion history suggested that intrinsic iron leading was a major factor in these patients. We conclude that leukemic transformation in AISA is a common, poorly predictable event which required lengthy followup for detection. Hemochromatosis in AISA occurs frequently and shortens the median survival.

Measurement of delta-aminolevulinic acid synthetase activity in human erythroblasts

A new, specific, and simple method for the determination of delta-aminolevulinic acid (ALA) synthetase activity in human bone marrow cells has been developed. ALA synthetase of erythroblasts was partially purified so as to permit the use of [(14)C]succinyl-CoA as a substrate for this enzyme. In this enzyme preparation there were negligible activities of succinyl-CoA hydrolase, alpha-ketoglutarate dehydrogenase, and succinyl-CoA synthetase and there was no activity of ALA dehydrase. The ALA formed from [(14)C]succinyl-CoA has been isolated by column chromatography. Radioactivity in the eluate from the column has been proved by paper chromatography to be exclusively that of [(14)C]ALA. The entire assay can be completed within 4 h, and [(14)C]succinyl-CoA was incorporated into [(14)C]ALA on the order of several percent. Moderate to marked decreases of ALA synthetase activity have been demonstrated in the erythroblasts of all cases of sideroblastic anemia. In the cases of iron deficiency anemia, on the other hand, normal or slightly elevated activity has been obtained.