Gotowa bibliografia na temat „Congenital Sideroblastic Anemia”

The sideroblastic anemias are a heterogeneous group of inherited and acquired disorders characterized by anemia and the presence of ring sideroblasts in the bone marrow. Ring sideroblasts are abnormal erythroblasts with iron-loaded mitochondria that are visualized by Prussian blue staining as a perinuclear ring of green-blue granules. The mechanisms that lead to the ring sideroblast formation are heterogeneous, but in all of them, there is an abnormal deposition of iron in the mitochondria of erythroblasts. Congenital sideroblastic anemias include nonsyndromic and syndromic disorders. Acquired sideroblastic anemias include conditions that range from clonal disorders (myeloid neoplasms as myelodysplastic syndromes and myelodysplastic/myeloproliferative neoplasms with ring sideroblasts) to toxic or metabolic reversible sideroblastic anemia. In the last 30 years, due to the advances in genomic techniques, a deep knowledge of the pathophysiological mechanisms has been accomplished and the bases for possible targeted treatments have been established. The distinction between the different forms of sideroblastic anemia is based on the study of the characteristics of the anemia, age of diagnosis, clinical manifestations, and the performance of laboratory analysis involving genetic testing in many cases. This review focuses on the differential diagnosis of acquired disorders associated with ring sideroblasts.

Abstract Abstract 5105 A-14 years-old man, admitted to our clinic with weakness and paleness since one month. He has hepatosplenomegaly. Blood tests and peripheral blood smear showed anemia that severe hypochromic, microcytic anemia. There is ringed sideroblasts without dysplastic hematopoiesis in bone marrow cytology. Liver tests were normal. A liver biopsy showed heavy parenchymal iron deposition and grade-III fibrosis. Screening for HFE gene mutations was negative. MR imaging demonstrated that severe iron accumulation in liver and heart. ALAS2 gene screening showed that novel mutation in exon 7 (Gly390Gly, c.1170, C□T). Eventually, was diagnosed as sideroblastic anemia and hemochromatosis. He was treated successfully with pyridoxine and chelating agent (deferasirox, IGL-670). The findings suggest that the Gly390Gly in ALAS2 mutation causes sideroblastic anemia and hemochromatosis, without hereditary hemochromatosis gene mutations. This mutation cause sideroblastic anemia is clinically pyridoxine-responsive. Deferasirox is effective agent for reduce hepatic iron loading in this condition. Disclosures Off Label Use: deferasiroks was used for hemochromatosis secondary to congenital syderoblastic anemia.

Abstract Abstract 2919 Background: Sideroblastic anemias can be either hereditary due to congenital mutations in factors critical for iron processing or heme biosynthesis, or acquired; acquired sideroblastic anemias may be induced by alcohol or medications, but are usually idiopathic. Pyridoxine, a form of vitamin B6, plays a critical role in heme synthesis as a cofactor for δ-aminolevulinic acid synthetase (ALAS). Some subtypes of congenital sideroblastic anemia, such as those associated with mutations in the ALAS2 gene encoding the erythrocyte-expressed isoform of ALAS, may respond to pyridoxine therapy at doses ranging from 5–500 mg/day. Anecdotal reports of improvement with pyridoxine therapy in cases of acquired idiopathic sideroblastic anemia (AISA) have led to widespread clinical use of this agent in patients with refractory anemia with ring(ed) sideroblasts (RARS) and refractory cytopenia with multilineage dysplasia associated with ring sideroblasts (RCMD-RS). However, there are no systematic studies of the effectiveness of pyridoxine in AISA. Methods: We reviewed clinical and laboratory data from 231 adult patients with marrow aspirate-proven AISA (i.e., RARS or RCMD-RS, based on 2001 WHO criteria) evaluated at our institution between 1994 and 2007. Responses to pyridoxine were assessed using 2006 International Working Group (IWG) standardized criteria for MDS (erythroid response with hemoglobin increase by '1.5 mg/dl). The relationship between response to pyridoxine and disease subtype or International Prognostic Scoring System (IPSS) stratification was assessed using χ2 test, using a p-value limit of <0.05 for statistical significance. Results: 86 of the 231 patients (42%) were treated with pyridoxine for an average of 19 months (range 1–114 months) at a mean dose of 167 mg/day (range 50–600 mg/day). Sufficient follow-up data to allow response evaluation were available from 74 (86%) of the 86 patients who received pyridoxine. Only 5/86 patients (6.8%) receiving pyridoxine met IWG response criteria for hematological improvement, but 3 of these 5 patients also received erythropoetin and 1 also received prednisone concomitantly with pyridoxine therapy. Therefore, only 1/86 (1.4%) patient's improvement in hemoglobin could be attributed to pyridoxine monotherapy. ALAS2 genotype data were not available from these 5 patients. The dose of pyridoxine was not associated with response to therapy (187.5 mg daily in responders vs. 157 mg daily in non-responders (p=0.60). Patients with RCMD-RS were more likely to be treated with vitamin B6 compared to patients with RARS (p=<0.001), possibly because of more severe anemia, but response to pyridoxine did not differ significantly between subtypes (3/49 vs. 2/25, response in RARS vs. RCMD-RS; p=0.76). Among the 74 evaluable patients, 3/46 patients in the low IPSS risk group responded to pyridoxine, compared to 2/24 of patients in the Intermediate-1 risk group and 0/4 in the Intermediate-2 risk group (p=0.82). Adverse effects associated with pyridoxine included new onset of irreversible symptomatic peripheral neuropathy in 2/86 patients (2.3%). Conclusions: Pyridoxine is commonly prescribed to patients with AISA in clinical practice, and this agent is often continued for a long period of time despite lack of evidence of objective response. Pyridoxine is an ineffective therapy in AISA that induces symptomatic peripheral neuropathy in some patients. Therefore, pyridoxine therapy should be limited to patients with known or suspected congenital mutations that confer pyridoxine responsiveness, and therapeutic trials should be brief to avoid adverse effects. Disclosures: No relevant conflicts of interest to declare.

ABSTRACT The porphyrias are a diverse group of metabolic disorders arising from diminished activity of enzymes in the heme biosynthetic pathway. They can present with acute neurovisceral symptoms, cutaneous symptoms, or both. The complexity of these disorders is demonstrated by the fact that some acute porphyria patients with the underlying genetic defect(s) are latent and asymptomatic while others present with severe symptoms. This indicates that there is at least one other risk factor required in addition to the genetic defect for symptom manifestation. A systematic review of the heme biosynthetic pathway highlighted the involvement of a number of micronutrient cofactors. An exhaustive review of the medical literature uncovered numerous reports of micronutrient deficiencies in the porphyrias as well as successful case reports of treatments with micronutrients. Many micronutrient deficiencies present with symptoms similar to those in porphyria, in particular vitamin B6. It is hypothesized that a vitamin B6 deficiency and related micronutrient deficiencies may play a major role in the pathogenesis of the acute porphyrias. In order to further investigate the porphyrias, a computational model of the heme biosynthetic pathway was developed based on kinetic parameters derived from a careful analysis of the literature. This model demonstrated aspects of normal heme biosynthesis and illustrated some of the disordered biochemistry of acute intermittent porphyria (AIP). The testing of this model highlighted the modifications necessary to develop a more comprehensive model with the potential to investigated hypotheses of the disordered biochemistry of the porphyrias as well as the discovery of new methods of treatment and symptom control. It is concluded that vitamin B6 deficiency might be the risk factor necessary in conjunction with the genetic defect to trigger porphyria symptoms.

Mitochondria are ubiquitous organelles placed at the nexus of several metabolic and signaling pathways essential for cell survival. Therefore, maintaining a healthy and functional organelle becomes paramount for the cell. The complex structural organization and the bi-genomic nature of the mitochondria pose a significant challenge in maintaining their homeostasis. In addition to the proteins encoded by the mitochondrial DNA (mtDNA), the mito-proteome primarily consists of nuclear-encoded proteins synthesized in the cytosol and subsequently translocated to the mitochondria. Thus, the biogenesis and functioning of the mitochondria are dependent on the efficient transport, folding, and localization of the nuclear-encoded proteins. Any disruptions in this chain of events can be detrimental to the mitochondria and, thereby, to the cell. As a result, several quality-control mechanisms have evolved that operate at multiple levels to abate any mitochondrial damage due to internal and external cellular stress. Within the mitochondria, the import, folding, targeting, and degradation of proteins are regulated by the molecular chaperones. Among these, the mitochondrial Hsp70 (mtHsp70) is a crucial mediator of protein quality control. In conjunction with multiple co-chaperones, mtHsp70 performs two critical functions: the vectorial import of the nascent polypeptides into the mitochondria and their subsequent folding within the matrix. At the organellar level, a quality check is monitored by the segregation and degradation of superfluous or dysfunctional mitochondria via the process of mitophagy. This is achieved by the concerted action of AuTophaGy (ATG) related proteins and the dynamics of the mitochondrial network. Interestingly, studies reveal that increased mitophagy mitigates the effects of mtHsp70 mutations identified in patients with Parkinson’s disease, thus, suggesting an overlap between the quality control pathways. However, the details and implications of this interaction remain unexplored. Thus, in the current study, we have employed an array of genetic and biochemical techniques in the yeast model system to understand the overlap between the quality checkpoints and, further, to delineate the involvement of mtHsp70-mediated quality control in the progression of Congenital Sideroblastic Anemia (CSA). We have explored how mtHsp70-mediated quality control engages and responds to the abrogation of mitophagy. Utilizing an unbiased genetic screen, we have identified mtHsp70 mutants that exhibit compromised growth without the mitophagy receptor, Atg32. This is accompanied by an alteration in the mitochondrial physiology, general autophagy, lipid homeostasis, and redox balance overall, resulting in a reduction in cellular lifespan. Our findings highlight the role of mtHsp70 in maintaining mitochondrial integrity under stress conditions and underscore the need for an overlap between the quality control pathways. Further, we have investigated the role of mtHsp70 in the onset and progression of Congenital Sideroblastic Anemia (CSA), a hereditary blood disorder characterized by the accumulation of iron-laden mitochondria. Preliminary analyses of analogous mutations in the yeast mtHsp70 reveal perturbations in the mitochondrial network and functionality. Further, we observe mutations in mtHsp70 impair its import and chaperone activity resulting in a loss of function that manifests as the disease phenotypes observed in Congenital Sideroblastic Anemia. The current study provides insights into the interaction between the various mitochondrial quality checkpoints and highlights the relevance of protein quality control in the context of Congenital Sideroblastic Anemia progression.
Indian Institute of Science

Congenital sideroblastic anemias (CSA) are inherited diseases resulting from defects in heme biosynthesis, mitochondrial iron-sulfur cluster (ISC) assembly, or mitochondrial translation. CSAs are characterized by pathological iron deposits in the mitochondria of bone marrow erythroblasts. Recently the Fleming Lab at Boston Children’s Hospital has reported mutations in HSPA9, a chaperone involved in ISC assembly, as a cause of nonsyndromic CSA. Here we identified a CSA patient harboring two variants in HSCB, encoding a binding partner of HSPA9: a paternally inherited promoter variant (c-134C>A) and a maternally inherited frameshift variant (T87fs) predicted to result in a truncated protein. To better understand the pathophysiology of these variants, we investigated HSCB protein expression and function in patient-derived skin fibroblasts. Patient fibroblasts show evidence of decreased HSCB protein levels. shRNA targeting HSCB was employed to specifically suppress HSCB expression in the K562 erythroid-like cell line model. shRNA-infected K562 cells presented with perturbed iron homeostasis, a shift to glycolytic energy production, and diminished hemoglobinization. Targeted deletion of murine Hscb is embryonic lethal prior day E7.0. Tissue-specific lox-Cre transgenic lines, including Vav-, EpoR- and Mx-Cre demonstrate that Hscb is essential for hematopoiesis and erythropoiesis. Mutant mice present with hematopoietic defects similar to the index patient. Vav-Cre animals die prior to post-natal day 9 with decreased red cell counts, white cell counts, and decreased hemoglobin compared to wild-type animals. Floxed-null EpoR-Cre animals die before embryonic day 13. To excise Hscb specifically in the hematopoietic compartment of adult animals, conditional Mx-Cre animals were generated through bone marrow transplantation and temporally induced with polyinosinic-polycytidylic acid treatment. The animals died 22 days post-injection with decreased red blood cells, white blood cells, hemoglobin, and an overall decline in hematopoiesis of the bone marrow. These data demonstrate that HSCB is required for erythropoiesis and hematopoiesis and that the patient mutations are a pathogenic cause of CSA.