Sideroblasts Research Articles

Engineered bacterial lipoate protein ligase A (lplA) restores lipoylation in cell models of lipoylation deficiency.

Protein lipoylation, a vital lysine posttranslational modification (PTM), plays a crucial role in the function of key mitochondrial TCA cycle enzymatic complexes. In eukaryotes, lipoyl PTM synthesis occurs exclusively through de novo pathways, relying on lipoyl synthesis/transfer enzymes, dependent upon mitochondrial fatty acid and Fe-S cluster biosynthesis. Dysregulation in any of these pathways leads to diminished cellular lipoylation. Efficient restoration of lipoylation in lipoylation deficiency cell states using either chemical or genetic approaches has been challenging due to pathway complexity and multiple upstream regulators. To address this challenge, we explored the possibility that a bacterial lipoate protein ligase (lplA) enzyme, that can salvage free lipoic acid bypassing the dependency on de novo synthesis, could be engineered to be functional in human cells. Overexpression of the engineered lplA in lipoylation null cells restored lipoylation levels, cellular respiration, and growth in low glucose conditions. Engineered lplA restored lipoylation in all tested lipoylation null cell models, mimicking defects in mitochondrial fatty acid synthesis (MECR KO), Fe-S cluster biosynthesis (BOLA3 KO), and specific lipoylation regulating enzymes (FDX1, LIAS and LIPT1 KOs). Furthermore, we describe a patient with a homozygous c.212C>T variant LIPT1 with a previously uncharacterized syndromic congenital sideroblastic anemia. K562 erythroleukemia cells engineered to harbor this missense LIPT1 allele recapitulate the lipoylation deficient phenotype and exhibit impaired proliferation in low glucose that is completely restored by engineered lplA. This synthetic approach offers a potential therapeutic strategy for treating lipoylation disorders.

Whole Blood Transcriptome Analysis in Congenital Anemia Patients.

Congenital anemias include a broad range of disorders marked by inherent abnormalities in red blood cells. These abnormalities include enzymatic, membrane, and congenital defects in erythropoiesis, as well as hemoglobinopathies such as sickle cell disease and thalassemia. These conditions range in presentation from asymptomatic cases to those requiring frequent blood transfusions, exhibiting phenotypic heterogeneity and different degrees of severity. Despite understanding their different etiologies, all of them have a common pathophysiological origin with congenital defects of erythropoiesis. We can find different types, from congenital sideroblastic anemia (CSA), which is a bone marrow failure anemia, to hemoglobinopathies as sickle cell disease and thalassemia, with a higher prevalence and clinical impact. Recent efforts have focused on understanding erythropoiesis dysfunction in these anemias but, so far, deep gene sequencing analysis comparing all of them has not been performed. Our study used Quant 3' mRNA-Sequencing to compare transcriptomic profiles of four sickle cell disease patients, ten thalassemia patients, and one rare case of SLC25A38 CSA. Our results showed clear differentiated gene map expressions in all of them with respect to healthy controls. Our study reveals that genes related to metabolic processes, membrane genes, and erythropoiesis are upregulated with respect to healthy controls in all pathologies studied except in the SLC25A38 CSA patient, who shows a unique gene expression pattern compared to the rest of the congenital anemias studied. Our analysis is the first that compares gene expression patterns across different congenital anemias to provide a broad spectrum of genes that could have clinical relevance in these pathologies.

A novel pathogenic variant in ALAS2 gene in young Indian male with X-linked sideroblastic anemia: a case report

BackgroundCongenital sideroblastic anemias are heterogenous disorders with variable phenotypic expression. The most common form is X-linked and is caused by pathogenic variants of the 5-aminolevulinate synthase 2 (ALAS2) enzyme of heme biosynthesis.Case presentationA 19 year old Indian young male presented with severe microcytic anemia. Bone marrow examination revealed ring sideroblasts. Using second generation sequencing, a novel pathogenic variant (Arg204Leu) was found in exon 5 of the ALAS2 gene, establishing the diagnosis of X-linked sideroblastic anemia. On treatment with oral pyridoxine supplement the patient’s hemoglobin level returned to normal.ConclusionsMore than 100 pathogenic variants in the ALAS2 gene have been reported to date. The Arg204Leu variant in our case adds to the XLSA pathogenic variant data base. The associated anemia is fully responsive to pyridoxine supplementation.

Myeloid neoplasm with concurrent BCR::ABL1 translocation, and JAK2 and SF3B1 co-mutations with severe fibrosis: a case report

Abstract Introduction/Objective Myeloproliferative neoplasms (MPNs) arise from hematopoietic stem cells with somatically altered tyrosine kinase signaling. Classification of MPNs is based on hematologic, histopathologic and molecular characteristics including the presence of BCR::ABL1 and JAK2 V617F. Methods/Case Report We present a 72-year-old male with a myeloid neoplasm and severe fibrosis, with concurrent BCR::ABL1 translocation, and co-mutations in JAK2 and SF3B1. Initially, the patient was diagnosed with anemia, thrombocytosis and folic acid deficiency and was prescribed supplemental folic acid. At follow up, normocytic anemia and thrombocytosis were seen. Bone marrow biopsy showed overtly fibrotic marrow with maturing trilineage hematopoiesis, markedly increased megakaryopoiesis and ring sideroblasts. Chromosome analysis and sequential GTG-fluorescence in situ hybridization (FISH) of metaphases using the dual-fusion three color probe BCR/ABL1- ASS1 revealed abnormal results. A t(9;22)(q34;q11.2) was detected along with an atypical FISH signal pattern with a single BCR::ABL1 fusion on the derivative chromosome 22 instead of the typical two fusions, resulting in loss of one BCR::ABL1 fusion signal including loss of the ASS1 on the derivative chromosome 9. Next-generation sequencing (NGS) analysis detected double driver mutations, JAK2 p. Val617Phe and SF3B1 p. Lys700Glu in the patient. JAK2 V617F mutation was further confirmed by real-time quantitative PCR (qPCR) with variant allele frequencies of 39.7%. Additionally, the patient was positive for BCR::ABL1 p190 fusion transcript (10%). The presence of JAK2 and SF3B1 co-mutations along with ring sideroblasts and the patient’s clinical presentation suggests the diagnosis of myelodysplastic/myeloproliferative neoplasm with thrombocytosis and SF3B1 mutation. Results (if a Case Study enter NA) NA Conclusion Although, the detection of t(9;22) by chromosome analysis is a diagnostic feature of chronic myeloid leukemia (CML), our case adds to the limited information on co-existence of BCR::ABL1 and JAK2 V617F with SF3B1 mutations in severe fibrosis. The frequency of co-occurrence, the temporal order of acquisition and clonal relationship of these alterations is poorly understood, and it is also unclear for this case since there is no prior bone marrow biopsy or diagnostic work up. Literature search of these rare cases show that some patients with similar findings progress to myelofibrosis as in this patient. It is possible that the presence of two mutated tyrosine kinase genes accelerates disease progression.

Co-existence of Myelodysplastic Disorders and Plasma Cell Neoplasms: Case Series

Abstract Introduction/Objective The development of myelodysplastic syndrome (MDS) in patients with plasma cell neoplasm (PCN) receiving treatment is well reported. However, co-occurrence of both, without any chemotherapy history, is sparsely documented in the literature. We aim to highlight the possible association between both. Methods/Case Report Database search was done using Epic Slicer-Dicer for cases with biopsy proven co-existing MDS and PCN (from 2010-2022). The patients’ charts were reviewed to collect and analyze the clinical features. Results (if a Case Study enter NA) We identified 3 patients, all in their seventies on presentation: First patient: man, presented with unexplained chronic anemia. Serum protein electrophoresis (SPEP) showed elevated levels of monoclonal IgG kappa (4.2 g/dl). Evaluation of the BM biopsy revealed MDS with low blasts (WHO-5) with IgG plasma cell myeloma (56% Kappa-restricted plasma cells). Chromosome analysis revealed normal karyotype. Molecular studies were not done. Second patient: man, with Rheumatoid Arthritis and anemia. SPEP revealed biclonal IgG lambda (2.0 g/dl). BM biopsy indicated 5-8% lambda-restricted plasma cell proliferation. Anemia was managed with darbopoetin, but without improvement. The patient did not get chemotherapy. Follow-up BM biopsy was done, showing MDS with low blasts and ringed sideroblasts (WHO-5) alongside the PCN. FISH showed two abnormal IGH rearrangement populations. Chromosome analysis revealed normal karyotype. Molecular studies were not done. Third patient: woman, with pancytopenia. SPEP indicated monoclonal protein IgG lambda (1.8 g/dl). BM biopsy revealed 10% lambda-restricted plasma cell proliferation, coexisting with MDS with increased blasts grade 2 (WHO-5). Molecular studies showed: 2-FLT3 L601_K602insNFREYEYDL and ASXL1 E635fs*15. Chromosome analysis revealed normal karyotype. No in common clinical findings found during chart reviewing the cases. Conclusion Further investigating the underlying pathology, bone marrow microenvironment, and molecular and cytogenetics abnormalities in a larger number of patients with co-existing MDS and PCN is important. Also, if there was an association, it is important to study the sequence of occurrence between them.

Experience with luspatercept therapy in patients with transfusion-dependent low-risk myelodysplastic syndromes in real-world clinical practice: exploring the positive effect of combination with erythropoietin alfa.

Luspatercept, an inhibitor of the transforming growth factor beta (TGF-β) pathway, is a novel treatment for anemic patients with lower-risk myelodysplastic syndromes (MDS) with transfusion dependence (TD) who do not respond to erythropoiesis-stimulating agents (ESA) therapy or are not suitable candidates for this treatment. We present real-world experience with luspatercept therapy from two hematology centers in the Czech Republic. By January 2024, 54 MDS patients (33 men, 21 women) with a median age of 74 years (range, 55-95) were treated with luspatercept ± ESA at two Charles University hematology centers in Prague and Hradec Králové. According to the WHO 2016 classification, the cohort included 32 MDS-RS-MLD, seven MDS-MLD, two patients with 5q- + ring sideroblasts (RS), 12 RARS-T, and 1 patient with CMML-0 + RS. SF3B1 mutation data were available for 45 patients. All patients were in the IPSS-R and IPSS-M lower-risk groups (except four IPSS-M high). The median follow-up was 17 months (range, 1-54). All patients were transfusion-dependent. Thirty-five (64.8%) patients had a high transfusion burden (HTB) with ≥ 4 transfusion units (TU)/8 weeks, and 19 (35.2%) had a low transfusion burden (LTB) (< 4 TU/8 weeks). The median time between diagnosis and initiation of luspatercept was 27 months (range, 4-156). ESA were used prior to luspatercept in 45 patients, and luspatercept was used as first-line treatment in nine patients. Thirty-one (61%) patients were treated simultaneously with ESA. Only patients who received luspatercept for ≥ 8 weeks (51 patients) were assessed. We evaluated the achievement of transfusion independence (TI) lasting 8, 12, 16, and 24 weeks. Thirty-two (62.7%) patients achieved TI for ≥ 8 weeks, 31 (60.7%) for ≥ 12 weeks, 29 (56.8%) for ≥ 16 weeks, and 25 (49%) for ≥ 24 weeks. Hematologic improvement (HI) without TI was achieved in six patients (11.7%). Overall, HI + TI was achieved in 38 patients (74.5%). Epoetin alfa was used simultaneously in 31 patients (60.7%). In 21 (55.2%) of all responding patients, concomitant therapy with epoetin alfa led to an improved response, with 16 reaching TI. Thirteen (25.5%) patients were nonresponders. Eight (21%) patients experienced therapy failure and became transfusion-dependent again. Optimal response required a gradual increase in the luspatercept dose to 1.75 mg/kg in up to 35 patients, with 23 responders (TI + HI). Response rates varied by transfusion burden: 79% in LTB and 50% in HTB reached TI. Of RS+ patients, 70% reached TI, while only one out of five RS- patients achieved TI. Among 39 SF3B1-positive patients, 61.6% achieved TI. In the low and very low IPSS-M groups, 86% of patients responded (TI + HI), compared to 62% in the moderate-low group. Luspatercept was well-tolerated, with no adverse events higher than grade II toxicity. We have demonstrated in real-world clinical practice that luspatercept is a very effective agent, even in an unselected, pretreated, significantly TD MDS population. The effect was particularly high in the IPSS-M low and very low groups. We believe that the relatively high response rate in our patients was influenced by the frequent use of a higher dose (1.75 mg/kg) and especially by adding ESA to luspatercept in poorly responding patients.

Genomic Landscape of Myelodysplastic/Myeloproliferative Neoplasms: A Multi-Central Study.

The accurate diagnosis and classification of myelodysplastic/myeloproliferative neoplasm (MDS/MPN) are challenging due to the overlapping pathological and molecular features of myelodysplastic syndrome (MDS) and myeloproliferative neoplasm (MPN). We investigated the genomic landscape in different MDS/MPN subtypes, including chronic myelomonocytic leukemia (CMML; n = 97), atypical chronic myeloid leukemia (aCML; n = 8), MDS/MPN-unclassified (MDS/MPN-U; n = 44), and MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T; n = 12). Our study indicated that MDS/MPN is characterized by mutations commonly identified in myeloid neoplasms, with TET2 (52%) being the most frequently mutated gene, followed by ASXL1 (38.7%), SRSF2 (34.7%), and JAK2 (19.7%), among others. However, the distribution of recurrent mutations differs across the MDS/MPN subtypes. We confirmed that specific gene combinations correlate with specific MDS/MPN subtypes (e.g., TET2/SRSF2 in CMML, ASXL1/SETBP1 in aCML, and SF3B1/JAK2 in MDS/MPN-RS-T), with MDS/MPN-U being the most heterogeneous. Furthermore, we found that older age (≥65 years) and mutations in RUNX1 and TP53 were associated with poorer clinical outcomes in CMML (p < 0.05) by multivariate analysis. In MDS/MPN-U, CBL mutations (p < 0.05) were the sole negative prognostic factors identified in our study by multivariate analysis (p < 0.05). Overall, our study provides genetic insights into various MDS/MPN subtypes, which may aid in diagnosis and clinical decision-making for patients with MDS/MPN.

Non-syndromic congenital sideroblastic anaemia; phenotype, and genotype of 15 Indian patients.

Sideroblastic anaemias are a diverse group of congenital and acquired bone marrow failure disorders marked by the presence of ring sideroblasts, ineffective erythropoiesis, and systemic iron overload. Congenital Sideroblastic anaemia (CSA) is mainly caused by gene mutations associated with heme synthesis, iron-sulfur [Fe-S] cluster, and mitochondrial protein synthesis pathways. The most prevalent form of CSA is caused by mutations in the erythroid-specific -amino levulinate synthase (ALAS2) gene, which encodes the first enzyme in the heme synthesis pathway in red blood cells. The second most prevalent form of CSA is caused by a mutation in the Solute carrier family 25 member 38 (SLC25A38) gene, which codes for an erythroid-specific protein of the inner mitochondrial membrane. Additionally, 15-20 genes are altogether associated with CSA. In this study, we aim to identify the CSA patients, understand their genetics and establish genotype-phenotype correlation. We have identified fifteen cases of CSA using our targeted NGS (t-NGS) panel. The major clinical findings in our cohort were microcytic anaemia, ring sideroblasts, and dyserythropoiesis in the bone marrow. Currently, two patients are responsive to pyridoxine, while the rest are on blood transfusion support. We have identified ten variants in three different genes of CSA (ALAS2, SLC25A38 & HSPA9). Five patients harbour four hemizygous variants- p.Ala282Ser, p.Arg170Cys, p.Arg204Gln and exon 2 duplication in the ALAS2 gene. In seven patients, we have identified three homozygous mutations - p.Pro190Arg, p.Arg187Gln and p.Arg134Cys in the SLC25A38 gene. These mutations have been predominantly identified in the European population. Three patients revealed three heterozygous variants p. Thr463Ile, D326Tyr, and Arg284Trp in the HSPA9 gene. PyMoL was used to evaluate the functional effects of these variations and understand their effect on the structure of the protein. We believe that by combining a bone marrow examination with genetic sequencing, CSA patients can acquire a definitive diagnosis.

Novel cellular models of SLC25A38-related congenital sideroblastic anemia shed light on mitochondrial physiology and pave the way for therapeutic strategies

Novel cellular models of SLC25A38-related congenital sideroblastic anemia shed light on mitochondrial physiology and pave the way for therapeutic strategies

Severe pulmonary arterial hypertension in congenital sideroblastic anemia from PUS1 mutation – a case report

BackgroundMyopathy, lactic acidosis and inherited sideroblastic anemia (MLASA) are a group of rare intriguing disorders with wider pathophysiological implications. One of the causes of MLASA is the mutation in PUS1 gene that encodes for pseudouridine synthase. This PUS1 mutation results in MLASA in which anemia and myopathy predominate. Severe pulmonary arterial hypertension has not been previously reported in patients with PUS1 gene mutation.Case reportA 17 year old girl with congenital sideroblastic anemia presented with worsening of breathlessness. Severe pulmonary artery hypertension was documented on investigations. A homozygous variant in exon 3 of gene PUS1,( chromosome 12:g.131932301 C > T c.430 C > T) was found on sanger sequencing.ConclusionWe document severe pulmonary arterial hypertension in a patient of congenital sideroblastic anemia from PUS1 gene. We hypothesis that cross talk with TGFb pathways might occur in PUS1 mutation, and that might cause severe PAH. This observation might have therapeutic implications.

Sideroblastic anemia Secondary to anti-tubercular Therapy in a Patient with Acute Promyelocytic Leukemia

Sideroblastic anemia Secondary to anti-tubercular Therapy in a Patient with Acute Promyelocytic Leukemia

Luspatercept versus epoetin alfa in erythropoiesis-stimulating agent-naive, transfusion-dependent, lower-risk myelodysplastic syndromes (COMMANDS): primary analysis of a phase 3, open-label, randomised, controlled trial

The preplanned interim analysis of the COMMANDS trial showed greater efficacy of luspatercept than epoetin alfa for treating anaemia in erythropoiesis-stimulating agent (ESA)-naive patients with transfusion-dependent, lower-risk myelodysplastic syndromes. In this Article, we report the results of the primary analysis of the trial. COMMANDS is a phase 3, open-label, randomised, controlled trial conducted at 142 sites in 26 countries. Eligible patients were those aged 18 years or older, with myelodysplastic syndromes of very low risk, low risk, or intermediate risk (as defined by the Revised International Prognostic Scoring System), who were ESA-naive and transfusion dependent, and had a serum erythropoietin concentration of less than 500 U/L. Patients were stratified by baseline red blood cell transfusion burden, serum erythropoietin concentration, and ring sideroblast status, and randomly allocated (1:1) to receive luspatercept (1·0-1·75 mg/kg body weight, subcutaneously, once every 3 weeks) or epoetin alfa (450-1050 IU/kg body weight, subcutaneously, once a week; maximum total dose 80 000 IU) for at least 24 weeks. The primary endpoint was red blood cell transfusion independence lasting at least 12 weeks with a concurrent mean haemoglobin increase of at least 1·5 g/dL (weeks 1-24), evaluated in the intention-to-treat population. The safety population included all patients who received at least one dose of treatment. This trial is registered with ClinicalTrials.gov (NCT03682536; active, not recruiting). Between Jan 2, 2019, and Sept 29, 2022, 363 patients were screened and randomly allocated: 182 (50%) to luspatercept and 181 (50%) to epoetin alfa. Median age was 74 years (IQR 69-80), 162 (45%) patients were female, and 201 (55%) were male. 289 (80%) were White, 44 (12%) were Asian, and two (1%) were Black or African American. 23 (6%) were Hispanic or Latino and 311 (86%) were not Hispanic or Latino. Median follow-up for the primary endpoint was 17·2 months (10·4-27·7) for the luspatercept group and 16·9 months (10·1-26·6) for the epoetin alfa group. A significantly greater proportion of patients in the luspatercept group reached the primary endpoint (110 [60%] vs 63 [35%]; common risk difference on response rate 25·4% [95% CI 15·8-35·0]; p<0·0001). Median follow-up for safety analyses was 21·4 months (IQR 14·2-32·4) for the luspatercept group and 20·3 months (12·7-30·9) for the epoetin alfa group. Common grade 3-4 treatment-emergent adverse events occurring among luspatercept recipients (n=182) were hypertension (19 [10%] patients), anaemia (18 [10%]), pneumonia (ten [5%]), syncope (ten [5%]), neutropenia (nine [5%]), thrombocytopenia (eight [4%]), dyspnoea (eight [4%]), and myelodysplastic syndromes (six [3%]); and among epoetin alfa recipients (n=179) were anaemia (14 [8%]), pneumonia (14 [8%]), neutropenia (11 [6%]), myelodysplastic syndromes (ten [6%]), hypertension (eight [4%]), iron overload (seven [4%]), and COVID-19 pneumonia (six [3%]). The most common serious treatment-emergent adverse events in both groups were pneumonia (nine [5%] luspatercept recipients and 13 [7%] epoetin alfa recipients) and COVID-19 (eight [4%] luspatercept recipients and ten [6%] epoetin alfa recipients). One death (due to acute myeloid leukaemia) considered to be luspatercept-related was reported at the interim analysis. Luspatercept represents a new standard of care for ESA-naive patients with transfusion-dependent, lower-risk myelodysplastic syndromes. Significantly more patients had red blood cell transfusion independence and haematological improvement with luspatercept than with epoetin alfa, with benefits observed across patient subgroups. Celgene and Acceleron Pharma.

Chronic myelomonocytic leukemia with ring sideroblasts/SF3B1 mutation presents with low monocyte count and resembles myelodysplastic syndromes with-RS/SF3B1 mutation in terms of phenotype and prognosis.

Chronic myelomonocytic leukemia (CMML) and myelodysplastic syndromes (MDS) with ring sideroblasts (RS) or SF3B1 mutation (MDS-RS/SF3B1) differ in many clinical features, but share others, such as anemia. RS and SF3B1 mutation can also be found in CMML. We compared CMML with and without RS/SF3B1 and MDS-RS/SF3B1 considering the criteria established by the 2022 World Health Organization classification. A total of 815 patients were included (CMML, n=319, CMML-RS/SF3B1, n=172 and MDS-RS/SF3B1, n=324). The percentage of RS was ≥15% in almost all CMML-RS/SF3B1 patients (169, 98.3%) and most (125, 72.7%) showed peripheral blood monocyte counts between 0.5 and 0.9 x109/L and low risk prognostic categories. CMML-RS/SF3B1 differed significantly from classical CMML in the main clinical characteristics, whereas it resembled MDS-RS/SF3B1. At a molecular level, CMML and CMML-RS/SF3B1 had a significantly higher frequency of mutations in TET2 (mostly multi-hit) and ASXL1 (p=0.013) and CMML had a significantly lower frequency of DNMT3A and SF3B1 mutations compared to CMML/MDS-RS/SF3B1. Differences in the median overall survival among the three groups were statistically significant: 6.75 years (95% confidence interval [CI] 5.41-8.09) for CMML-RS/SF3B1 vs. 3.17 years (95% CI 2.56-3.79) for CMML vs. 16.47 years (NA) for MDS-RS/SF3B1, p<0.001. Regarding patients with CMML and MDS, both with SF3B1 mutation, survival did not significantly differ. CMML had a higher risk of transformation to acute myeloid leukemia (24% at 8 years, 95%CI 19%-30%). CMML-RS/SF3B1 mutation resembles MDS-RS/SF3B1 in terms of phenotype and clearly differs from CMML. The presence of ≥15% RS and/or SF3B1 in CMML is associated with a low monocyte count. SF3B1 mutation clearly improves the prognosis of CMML.

Pseudothrombocytosis: A Hint for Diagnosing a Case of Myelodysplastic Syndrome with Ring Sideroblast and 5q Deletion

Pseudothrombocytosis: A Hint for Diagnosing a Case of Myelodysplastic Syndrome with Ring Sideroblast and 5q Deletion

Murine models of erythroid 5ALA synthesis disorders and their conditional synthetic lethal dependency on pyridoxine

AbstractX-linked sideroblastic anemia (XLSA) and X-linked protoporphyria (XLPP) are uncommon diseases caused by loss-of-function and gain-of-function mutations, respectively, in the erythroid form of 5-aminolevulinic acid synthetase (ALAS), ALAS2, which encodes the first enzyme in heme biosynthesis. A related congenital sideroblastic anemia (CSA) is due to mutations in SLC25A38 (solute carrier family 25 member A38), which supplies mitochondrial glycine for ALAS2 (SLC25A38–CSA). The lack of viable animal models has limited the studies on pathophysiology and development of therapies for these conditions. Here, using CRISPR-CAS9 gene editing technology, we have generated knockin mouse models that recapitulate the main features of XLSA and XLPP; and using conventional conditional gene targeting in embryonic stem cells, we also developed a faithful model of the SLC25A38-CSA. In addition to examining the phenotypes and natural history of each disease, we determine the effect of restriction or supplementation of dietary pyridoxine (vitamin B6), the essential cofactor of ALAS2, on the anemia and porphyria. In addition to the well-documented response of XLSA mutations to pyridoxine supplementation, we also demonstrate the relative insensitivity of the XLPP/EPP protoporphyrias, severe sensitivity of the XLSA models, and an extreme hypersensitivity of the SLC25A38-CSA model to pyridoxine deficiency, a phenotype that is not shared with another mouse hereditary anemia model, Hbbth3/+ β-thalassemia intermedia. Thus, in addition to generating animal models useful for examining the pathophysiology and treatment of these diseases, we have uncovered an unsuspected conditional synthetic lethality between the heme synthesis–related CSAs and pyridoxine deficiency. These findings have the potential to inform novel therapeutic paradigms for the treatment of these diseases.

Elucidating the Role of Human ALAS2 C-terminal Mutations Resulting in Loss of Function and Disease.

The conserved enzyme aminolevulinic acid synthase (ALAS) initiates heme biosynthesis in certain bacteria and eukaryotes by catalyzing the condensation of glycine and succinyl-CoA to yield aminolevulinic acid. In humans, the ALAS isoform responsible for heme production during red blood cell development is the erythroid-specific ALAS2 isoform. Owing to its essential role in erythropoiesis, changes in human ALAS2 (hALAS2) function can lead to two different blood disorders. X-linked sideroblastic anemia results from loss of ALAS2 function, while X-linked protoporphyria results from gain of ALAS2 function. Interestingly, mutations in the ALAS2 C-terminal extension can be implicated in both diseases. Here, we investigate the molecular basis for enzyme dysfunction mediated by two previously reported C-terminal loss-of-function variants, hALAS2 V562A and M567I. We show that the mutations do not result in gross structural perturbations, but the enzyme stability for V562A is decreased. Additionally, we show that enzyme stability moderately increases with the addition of the pyridoxal 5'-phosphate (PLP) cofactor for both variants. The variants display differential binding to PLP and the individual substrates compared to wild-type hALAS2. Although hALAS2 V562A is a more active enzyme in vitro, it is less efficient concerning succinyl-CoA binding. In contrast, the M567I mutation significantly alters the cooperativity of substrate binding. In combination with previously reported cell-based studies, our work reveals the molecular basis by which hALAS2 C-terminal mutations negatively affect ALA production necessary for proper heme biosynthesis.

ATP-Binding Cassette Transporter of Clinical Significance: Sideroblastic Anemia.

The ATP-binding cassette (ABC) transporters are a vast group of 48 membrane proteins, some of which are of notable physiological and clinical importance. Some ABC transporters are involved in functions such as the transport of chloride ions, bilirubin, reproductive hormones, cholesterol, and iron. Consequently, genetic or physiological disruption in these functions is manifested in various disease processes like cystic fibrosis, Tangier disease, and sideroblastic anemia. Among other etiologies, primary sideroblastic anemia results from a genetic mutation in the ATP-binding cassette-7 (ABCB7), a member of the ABC transporter family. There are not many articles specifically tackling the disease processes caused by ABC transporters in detail. Some testing methodologies previously reported in the available literature for investigating sideroblastic anemia need updating. Here, we expound on the relevance of ABCB7 as a clinically important ABC transporter and a rare participant in the disease process of Sideroblastic anemia. The other genetic and secondary etiologies of sideroblastic anemia, which do not involve mutations in the ABCB7 protein, are also described. We review the pathophysiology, clinical course, symptoms, diagnosis, and treatment of sideroblastic anemia with a focus on modern technologies for laboratory testing.

Hematologic Manifestations in Primary Mitochondrial Diseases.

Primary mitochondrial disorders (PMDs) are known for their pleiotropic manifestations in humans, affecting almost any organ or system at any time. Hematologic manifestations, such as cytopenias and sideroblastic anemia, occur in 10% to 30% of patients with confirmed PMDs. These can be the initial presenting features or complications that develop over time. Surveillance for these manifestations allows for prompt identification and treatment. This article provides an overview of the pathophysiology underpinning the hematologic effects of mitochondrial dysfunction, discussing the 3 key roles of the mitochondria in hematopoiesis: providing energy for cell differentiation and function, synthesizing heme, and generating iron-sulfur clusters. Subsequently, the diagnosis and management of mitochondrial disorders are discussed, focusing on hematologic manifestations and the specific conditions commonly associated with them. Through this, we aimed to provide a concise point of reference for those considering a mitochondrial cause for a patient's hematologic abnormality, or for those considering a hematologic manifestation in a patient with known or suspected mitochondrial disease.

Clinical benefit of luspatercept treatment (tx) in transfusion-dependent (TD), erythropoiesis-stimulating agent (ESA)–naive patients (pts) with very low-, low- or intermediate-risk myelodysplastic syndromes (MDS) in the COMMANDS trial.

6565 Background: There is an unmet need for effective tx that provides durable benefit for pts with anemia due to lower-risk MDS (LR-MDS). Here we report clinically meaningful responses to luspatercept tx in TD, ESA-naive pts with LR-MDS in the COMMANDS trial. Methods: Eligible pts were ≥ 18 years of age, had LR-MDS with or without ring sideroblasts and &lt; 5% bone marrow blasts, endogenous serum erythropoietin &lt; 500 U/L, required red blood cell (RBC) transfusions (defined as 2−6 RBC units/8 weeks [wk] for ≥ 8 wk prior to randomization), and were ESA-naive. Pts were randomized 1:1 to subcutaneous administration of luspatercept (1.0–1.75 mg/kg) once every 3 wk or epoetin alfa (EA; 450–1050 IU/kg) once weekly for ≥ 24 wk. New assessments of clinical benefit reported here include achievement and duration of ≥ 50% reduction in RBC units transfused over ≥ 12 wk (wk 1–end of tx [EOT]), transfusion burden (TB) on tx (wk 1–24), time to first transfusion, achievement and cumulative duration of all separate RBC transfusion independence (RBC-TI) ≥ 12 wk response episodes, and mean hemoglobin (Hb) increase ≥ 1.5 g/dL over wk 1–24. Results: As of March 31, 2023, 151/182 (83.0%) luspatercept- and 121/181 (66.9%) EA-treated pts achieved ≥ 50% reduction in RBC units transfused over ≥ 12 wk (wk 1–EOT; P= 0.0002), with median (95% confidence interval [CI]) durations of 130.0 (120.6–not evaluable [NE]) and 77.0 (54.9–123.1) wk, respectively ( P = 0.0004). A greater proportion of luspatercept vs EA pts achieved ≥ 50% reduction in RBC units transfused over ≥ 12 wk (wk 1–EOT), regardless of baseline (BL) TB: 105/118 (89.0%) luspatercept vs 82/111 (73.9%) EA pts with BL TB &lt; 4 RBC units/8 wk and 46/64 (71.9%) luspatercept vs 39/70 (55.7%) EA pts with TB ≥ 4 RBC units/8 wk. The median (interquartile range) number of RBC units transfused during wk 1–24 of tx was 1.0 (0–5.0) in the luspatercept arm and 3.0 (0–8.0) in the EA arm. The median (95% CI) time to first transfusion was 155.0 (80.0–266.0) days for luspatercept vs 42.0 (23.0–55.0) days for EA pts ( P &lt; 0.0001). Among pts who achieved RBC-TI ≥ 12 wk (wk 1–24), 22/124 (17.7%) luspatercept pts vs 12/88 (13.6%) EA pts achieved ≥ 2 separate RBC-TI ≥ 12 wk response episodes and cumulative median (95% CI) duration of all response episodes was 147.9 (122.0–NE) wk in the luspatercept arm and 95.1 (73.1–NE) wk in the EA arm ( P = 0.0067). Mean Hb increase ≥ 1.5 g/dL over wk 1–24 was achieved by 135/182 (74.2%) luspatercept pts and 95/181 (52.5%) EA pts ( P &lt; 0.0001). Conclusions: Significantly greater proportions of luspatercept vs EA pts achieved improvements in Hb levels, reduction in TB and RBC units transfused, and had durable RBC-TI responses. Luspatercept provided clinically meaningful outcomes, supporting its use as the preferred tx for ESA-naive pts with LR-MDS-associated anemia. Clinical trial information: NCT03682536 .

Treatment of Anemia in Lower-Risk Myelodysplastic Syndrome.

A majority of patients with lower-risk myelodysplastic syndrome (MDS) will present with or develop anemia. Anemia in MDS is associated with decreased quality of life and may correlate with decreased progression-free survival and overall survival. In this state of the art review we summarize current risk stratification approaches to identify lower-risk MDS (LR-MDS), the natural history of the disease, and meaningful clinical endpoints. The treatment landscape of LR-MDS with anemia is also rapidly evolving; we review the role of supportive care, erythropoietin stimulating agents, lenalidomide, luspatercept, hypomethylating agents (HMAs), and immunosuppressive therapy (IST) in the management of LR-MDS with anemia. In patients with deletion 5q (del5q) syndrome lenalidomide has both efficacy and durability of response. For patients without del5q who need treatment, the management approach is impacted by serum erythropoietin (EPO) level, SF3B1 mutation status, and ring sideroblast status. Given the data from the Phase III COMMANDS trial, we utilize luspatercept in those with SF3B1 mutation or ring sideroblasts that have an EPO level < 500 U/L; in patients without an SF3B1 mutation or ring sideroblasts there is equipoise between luspatercept and use of an erythropoietin stimulating agent (ESA). For patients who have an EPO level ≥ 500 U/L or have been previously treated there is not a clear standard of care. For those without previous luspatercept exposure it can be considered particularly if there is an SF3B1 mutation or the presence of ring sideroblasts. Other options include HMAs or IST; the Phase III IMERGE trial supports the efficacy of the telomerase inhibitor imetelstat in this setting and this may become a standard option in the future as well.