Recent advances in β-thalassemias

β-thalassemias are heterogeneous hereditary anemias characterized by a reduced output of β-globin chains. The disease is most frequent in the temperate regions of the world, where it represents an important health problem. In the last decades, several programs, aimed at controlling the birth rate of thalassemia newborns by screening and prenatal diagnosis of populations with high risk of β-thalassemia, have been successful accomplished. Bone marrow transplantation has offered a definitive cure for the fraction of patients with available donors. In the same time, steady improvements were made in the traditional clinical management of β-thalassemia patients. The introduction of the oral iron chelators deferiprone that preferentially chelates hearth iron and the development of novel NMR diagnostic methods has led to reduced morbility, increased survival and improved quality of life. More recently, major advances have being made in the discovery of critical modifier genes, such as Myb and especially BCL11A (B cell lymphoma 11A), a master regulator of HbF (fetal hemoglobin) and hemoglobin switching. Polimorphysms of BCL11A, Myb and γ-globin genes account for most of the variability in the clinical phenotypes in β-thalassemia and sickle cell anemia patients. Finally, the year 2010 has brought in the first successful experiment of gene therapy in a β-thalassemia patient, opening up the perspective of a generalized cure for all β- thalassemia patients

Efficacy and safety of deferasirox doses of >30 mg/kg per d in patients with transfusion-dependent anaemia and iron overload

The highest approved dose of deferasirox is currently 30 mg/kg per d in many countries; however, some patients require escalation above 30 mg/kg per d to achieve their therapeutic goals. This retrospective analysis investigated the efficacy (based on change in serum ferritin levels) and safety of deferasirox >30 mg/kg per d in adult and paediatric patients with transfusion-dependent anaemias, including β-thalassaemia, sickle cell disease and the myelodysplastic syndromes. In total, 264 patients pooled from four clinical trials received doses of >30 mg/kg per d; median exposure to deferasirox >30 mg/kg per d was 36 weeks. In the overall population there was a statistically significant median decrease in serum ferritin of 440 μg/l (P< 0·0001) from pre-dose-escalation to the time-of-analysis; significant decreases were also observed in adult and paediatric patients, as well as β-thalassaemia patients. The adverse event profile in patients who received deferasirox doses of >30 mg/kg per d was consistent with previously published data. There was no worsening of renal or liver function following dose escalation. Deferasirox >30 mg/kg per d effectively reduced iron burden to levels lower than those achieved prior to dose escalation in patients with transfusion-dependent anaemias. This has important implications for patients who are heavily transfused and may require higher doses to reduce body iron burden

Iron overload across the spectrum of non-transfusion-dependent thalassaemias: role of erythropoiesis, splenectomy and transfusions

Non-transfusion-dependent thalassaemias (NTDT) encompass a spectrum of anaemias rarely requiring blood transfusions. Increased iron absorption, driven by hepcidin suppression secondary to erythron expansion, initially causes intrahepatic iron overload. We examined iron metabolism biomarkers in 166 NTDT patients with β thalassaemia intermedia (n = 95), haemoglobin (Hb) E/β thalassaemia (n = 49) and Hb H syndromes (n = 22). Liver iron concentration (LIC), serum ferritin (SF), transferrin saturation (TfSat) and non-transferrin-bound iron (NTBI) were elevated and correlated across diagnostic subgroups. NTBI correlated with soluble transferrin receptor (sTfR), labile plasma iron (LPI) and nucleated red blood cells (NRBCs), with elevations generally confined to previously transfused patients. Splenectomised patients had higher NTBI, TfSat, NRBCs and SF relative to LIC, than non-splenectomised patients. LPI elevations were confined to patients with saturated transferrin. Erythron expansion biomarkers (sTfR, growth differentiation factor-15, NRBCs) correlated with each other and with iron overload biomarkers, particularly in Hb H patients. Plasma hepcidin was similar across subgroups, increased with >20 prior transfusions, and correlated inversely with TfSat, NTBI, LPI and NRBCs. Hepcidin/SF ratios were low, consistent with hepcidin suppression relative to iron overload. Increased NTBI and, by implication, risk of extra-hepatic iron distribution are more likely in previously transfused, splenectomised and iron-overloaded NTDT patients with TfSat >70%

Combined therapy with deferiprone and desferrioxamine in thalassemia major

Effective and convenient iron chelation remains one of the main targets of clinical management of thalassemia major. The combined treatment with desferrioxamine and deferiprone could have an increased chelation efficacy and sometimes allow drug doses and toxicity to be reduced and the number of days of desferrioxamine infusion to be decreased, improving compliance and quality of life

A mutation in the TMPRSS6 gene, encoding a transmembrane serine protease that suppresses hepcidin production, in familial iron deficiency anemia refractory to oral iron.

Background Hepcidin plays a key role in body iron metabolism by preventing the release of iron from macrophages and intestinal cells. Defective hepcidin synthesis causes iron loading, while overproduction results in defective reticuloendothelial iron release and iron absorption. Design and Methods We studied a Sardinian family in which microcytic anemia due to defective iron absorption and utilization is inherited as a recessive character. Five members showed iron deficiency anemia that was not responsive to oral iron and only partially responsive to parenteral iron administration. To investigate the involvement of known genes implicated in iron metabolism we carried out linkage analysis with microsatellite markers mapping close to these genes. Afterwards, a genome-wide search was performed. Results No linkage was found between the phenotype of the patients and several known human genes involved in iron metabolism ( DMT1, TF, TFRC, ZIRTL, HAMP, HJV ). Genome-wide scanning by microsatellites and single nucleotide polymorphisms showed a multipoint LOD score of 5.6 on chromosome 22q12.3–13.1, where the matriptase-2 (also known as transmembrane protease, serine 6 or TMPRSS6 ) gene is located. Its murine counterpart ( Tmprss6 ) has recently been found to be an essential component of a pathway that detects iron deficiency and suppresses hepcidin production. Sequencing analysis of TMPRSS6 revealed a homozygous causal mutation, predicting a splicing error and a truncated TMPRSS6 protein in affected members. Homozygous subjects had inappropriately elevated levels of serum and urinary hepcidin. Conclusions The findings of this study suggest that the observed TMPRSS6 mutation leads to overproduction of hepcidin and, in turn, to defective iron absorption and utilization. More generally, they confirm in humans the inhibitory effect of matriptase-2 on hepcidin synthesis already demonstrated in mice

Evaluation of an automatic HPLC analyser for thalassemia and haemoglobin variants screening

In this paper the authors report the evolution of a new automatic HPLC analyser for screening haemoglobinopathies. HbA2 and F determinations are accurate and reproducible. The analysis time is short (6.5 min) and there is a good separation between the HbA2 values of β-thalassemia carriers from normals and α-thalassemia carriers, with no overlap between these groups. In addition, the system is also able to detect and quantitate most of the haemoglobin variants, particularly those (HbS, HbC, HbE and Hb Lepore) able to interact with β-thalassemia and could make haemoglobin electrophoresis unnecessary in all samples. The ease of operation and the limited technical work make this system especially suitable for laboratories with a high workload and allow the cost of screening to be reduced

Structural and Functional Characterization of a New Double Variant Haemoglobin (HbG-Philadelphia/Duarte α268Asn→Lysβ262Ala→Pro)

We report the first case of cosegregation of two haemoglobins (Hbs): HbG-Philadelphia [α68(E17)Asn → Lys] and HbDuarte [β62(E6)Ala → Pro]. The proband is a young patient heterozygous also for β°-thalassaemia. We detected exclusively two haemoglobin variants: HbDuarte and HbG-Philadelphia/Duarte. Functional study of the new double variant HbG-Philadelphia/Duarte exhibited an increase in oxygen affinity, with a slight decrease of cooperativity and Bohr effect. This functional behaviour is attributed to β62Ala → Pro instead of α68Asn → Lys substitution. Indeed, HbG-Philadelphia isolated in our laboratory from blood cells donor carrier for this variant is not affected by any functional modification, whereas purified Hb Duarte showed functional properties very similar to the double variant. NMR and MD simulation studies confirmed that the presence of Pro instead of Ala at the β62 position produces displacement of the E helix and modifications of the tertiary structure. The substitution α68(E17)Asn → Lys does not cause significant structural and dynamical modifications of the protein. A possible structure-based rational of substitution effects is suggested