Advances in the pathophysiology and treatment of thalassemia

Increased Endothelial Cell Density in Childhood Patients With Thalassemia Major

PURPOSE

We aimed to compare specular microscopy, biometric, refractive, and anterior segment topographic parameters in children with thalassemia major (TM) with normal children of the same age.

MATERIAL METHOD

This cross-sectional study included 55 eyes of 55 patients with TM and 63 eyes of 63 age-sex-matched healthy children; all patients with TM were receiving treatment with blood transfusions every 3 to 4 weeks and an oral iron chelator deferasirox (DFX) (ICL670) tablet. A comprehensive ophthalmic examination was performed, including refraction (spherical equivalent), best-corrected visual acuity, slit-lamp bio microscopy, specular examination, optical biometry, intraocular pressure, anterior segment topography, and fundus examination.

RESULTS

Endothelial cell density (ECD) was 3,138 in the TM group and 2,996 in the control group (P=0.003). The mean central corneal thickness was significantly thinner in the TM group (P=0.010). Flat keratometry (K1) was 43.5 D in the study group and 42.9 D in the control group (P=0.039). The mean anterior chamber depth (ACD) was shallower in the TM group (P=0.004); axial length (AL) was significantly shorter in the TM group (P=0.002).

CONCLUSION

This study shows that there are differences in ECD, AL, keratometry values, ACD, and anterior segment parameters of pediatric patients with TM compared with healthy controls.

Blood Demand and Challenges for Patients With Beta-Thalassemia Major in Eastern Saudi Arabia

Background

β-thalassemia major is a hereditary disorder of hemoglobin (Hb) that results in defective Hb synthesis, leading to severe chronic anemia. The mainstay of its treatment is lifelong regular packed red cell transfusions associated with iron-chelating therapy. Globally, there is a gap between blood donation and the actual needs of the patients who depend on transfusion. Patients with β-thalassemia major are no exception and have limited access to regular and safe blood transfusions. This study aimed to assess the gap between the demand and supply of blood for transfusion-dependent patients with β-thalassemia major treated at the Hereditary Blood Diseases Center, Al Ahsa, Eastern Saudi Arabia.

Methodology

This was a retrospective, cross-sectional study conducted at the Hereditary Blood Disease Center, Al Ahsa, Saudi Arabia, including patient data from January 2017 to December 2019. We used Excel 365 from Microsoft Office 2016, version 1706.

Results

A total of 158 patients were on chronic transfusion. Of the total patients, 65% were adults, while the remaining 35% comprised the pediatric population. The total number of units requested and received during the three-year period was 14,509 and 9,530, respectively, indicating a gap of 4,979 (34%) units. The age of most of the units received was more than 14 days: 36% of those in 2017, 49.9% in 2018, and 61.5% in 2019. Rare blood groups and alloimmunization accounted for <8% of the patients. Prestorage filtration was the policy for all units.

Conclusions

There was a gap between the demand and supply of blood for patients with β-thalassemia major treated at our center. We suggest raising awareness regarding the high demands for fresh red blood cell components in patients with thalassemia major, encouraging voluntary blood donations, enhancing national blood-banking policies, and reducing the fragmentation of blood services to reduce the gap between demand and supply.

Challenges of blood transfusions in β-thalassemia

Patients with β-thalassemia major (BTM) require regular blood transfusions, supported by appropriate iron chelation therapy (ICT), throughout their life. β-thalassemia is a global disease that is most highly prevalent in Southeast Asia, Africa, and Mediterranean countries. However, the global distribution of patients with β-thalassemia is changing due to population migration, and Northern European countries now have significant thalassemia populations. Globally, many patients with BTM have limited access to regular and safe blood transfusions. A lack of voluntary nonremunerated blood donors, poor awareness of thalassemia, a lack of national blood policies, and fragmented blood services contribute to a significant gap between the timely supply of, and demand for, safe blood. In many centers, there is inadequate provision of antigen testing, even for common red cell antigens such as CcEe and Kell. Policies to raise awareness and increase the use of red blood cell antigen testing and requesting of compatible blood in transfusion centers are needed to reduce alloimmunization (the development of antibodies to red blood cell antigens), which limits the effectiveness of transfusions and the potential availability of blood. Patients with BTM are also at risk of transfusion-transmitted infections unless appropriate blood screening and safety practices are in place. Hence, many patients are not transfused or are undertransfused, resulting in decreased health and quality-of-life outcomes. Hemovigilance, leukoreduction, and the ability to thoroughly investigate transfusion reactions are often lacking, especially in resource-poor countries. ICT is essential to prevent cardiac failure and other complications due to iron accumulation. Despite the availability of potentially inexpensive oral ICT, a high proportion of patients suffer complications of iron overload and die each year due to a lack of, or inadequate, ICT. Increased awareness, training, and resources are required to improve and standardize adequate blood transfusion services and ICT among the worldwide population of patients with BTM. ICT needs to be available, affordable, and correctly prescribed. Effective, safe, and affordable new treatments that reduce the blood transfusion burden in patients with β-thalassemia remain an unmet need.

Heparin-Induced Thrombocytopenia: A Comprehensive Clinical Review

Heparin-induced thrombocytopenia is a profoundly dangerous, potentially lethal, immunologically mediated adverse drug reaction to unfractionated heparin or, less commonly, to low-molecular weight heparin. In this comprehensive review, the authors highlight heparin-induced thrombocytopenia's risk factors, clinical presentation, pathophysiology, diagnostic principles, and treatment. The authors place special emphasis on the management of patients requiring procedures using cardiopulmonary bypass or interventions in the catheterization laboratory. Clinical vigilance of this disease process is important to ensure its recognition, diagnosis, and treatment. Misdiagnosis of the syndrome, as well as misunderstanding of the disease process, continues to contribute to its morbidity and mortality.

Protection against oxidative stress in beta thalassemia/hemoglobin E erythrocytes by inhibitors of glutathione efflux transporters

In beta thalassemia/hemoglobin E (Hb E), abnormally high levels of oxidative stress account for accelerated senescence and increased destruction of erythrocytes. The present study aimed to investigate the role of glutathione efflux transporters, namely cystic fibrosis transmembrane conductance regulator (CFTR) and multidrug resistance-associated protein 1 (MRP1), in the control of glutathione levels and protection against oxidative challenges in beta thalassemia/Hb E erythrocytes. We found that CFTR protein was expressed in the erythrocytes of beta thalassemia/Hb E patients. Treatments with GlyH-101 (50 µM), a small molecule CFTR inhibitor, and MK571 (50 µM), an MRP1 inhibitor, reduced H₂O₂-induced free radical generation in the erythrocytes by ∼80% and 50%, respectively. Furthermore, combined treatment with GlyH-101 and MK571 completely abolished the induction of reactive oxygen radicals. Increased oxidative stress in the erythrocytes following H₂O₂ challenges was accompanied by a decrease in intracellular level of reduced glutathione (GSH), which was prevented by treatments with GlyH-101 and MK571. CMFDA-based assays revealed that GlyH-101 and MK571 reduced H₂O₂-induced glutathione efflux from the erythrocytes by 87% and 66%, respectively. Interestingly, H₂O₂-induced osmotic tolerance of erythrocytes, a sign of erythrocyte aging, was ameliorated by treatment with GlyH-101. Our study indicates that oxidative stress induces glutathione efflux via CFTR and MRP1 in beta thalassemia/Hb E erythrocytes. Pharmacological inhibition of glutathione efflux represents a potential therapy to delay aging and premature destruction of erythrocytes in beta thalassemia/Hb E.

Insight onto the pathophysiology and clinical complications of thalassemia intermedia

Our understanding of the molecular and pathophysiological mechanisms underlying the disease process in patients with thalassemia intermedia (TI) has substantially increased over the past decade. TI encompasses a wide clinical spectrum of beta-thalassemia phenotypes. Some TI patients are asymptomatic until adult life, whereas others are symptomatic from as young as 2 years. A number of clinical complications commonly associated with TI are rarely seen in thalassemia major, including extramedullary hematopoiesis, leg ulcers, gallstones, thrombosis, and pulmonary hypertension. There are a number of options currently available for managing patients with TI, including transfusion therapy, iron chelation therapy, modulation of fetal hemoglobin production, and hematopoietic stem cell transplantation. However, at present, there are no clear guidelines for an orchestrated optimal treatment plan.

Thalassaemia intermedia: an update

Our understanding of the molecular and pathophysiological mechanisms underlying the disease process in patients with thalassaemia intermedia (TI) has substantially increased over the past decade. TI encompasses a wide clinical spectrum of beta-thalassaemia phenotypes. Some TI patients are asymptomatic until adult life, whereas others are symptomatic from as young as 2 years of age. A number of clinical complications commonly associated with TI are rarely seen in thalassaemia major, including extramedullary hematopoiesis, leg ulcers, gallstones, thrombosis and pulmonary hypertension. There are a number of options currently available for managing patients with TI, including transfusion therapy, iron chelation therapy, modulation of foetal haemoglobin production and haematopoietic stem cell transplantation. However, at present, there are no clear guidelines for an orchestrated optimal treatment plan.

Thalassemia intermedia: Revisited

Thalassemia intermedia encompasses a wide clinical spectrum of beta-thalassemia phenotypes. Some thalassemia intermedia patients are asymptomatic until adult life, whereas others are symptomatic from as young as 2 years of age. A number of clinical complications commonly associated with thalassemia intermedia are rarely seen in thalassemia major, including extramedullary hematopoiesis, leg ulcers, gallstones and thrombophilia. Prevention of these complications, possibly with blood transfusion therapy, is ideal since they may be difficult to manage. Currently, many patients with thalassemia intermedia receive only occasional or no transfusions, since they are able to maintain hemoglobin levels between 7-9 g/dl; the risk of iron overload, necessitating adequate chelation therapy, is also a contributing factor. At present, there are no clear guidelines for initiating and maintaining transfusions in thalassemia intermedia for the prevention or treatment of complications. Here, we review the major clinical complications in thalassemia intermedia and suggest some therapeutic strategies based on retrospective clinical observations.

New trends in the treatment of beta-thalassemia

Thalassemia is the world's most common hereditary disease, and is a paradigm of monogenic genetic diseases. Because of increased population mobility, the disease is found today throughout the world, even in places far from the tropical areas in which it arose. Therapy of thalassemia has in the past been confined to transfusion and chelation. Recently, novel modes of therapy have been developed for thalassemia, based on the pathophysiology and molecular pathology of the disease, both of which have been extensively studied. This review will discuss the therapeutic modalities currently in use for the supportive treatment of thalassemia, both those that are standard therapy and those that are in clinical trials. We will include transfusion, chelation (intravenous and oral), antioxidants and various inducers of fetal hemoglobin (hydroxyurea, erythropoietin, butyrates, hemin). Most of the newer therapies are suitable primarily for thalassemia intermedia patients. In addition, the treatment modalities currently in use for the curative treatment of thalassemia major will be discussed, including bone marrow transplantation in its various forms. Experimental therapeutic methods, such as intrauterine bone marrow transplantation and gene therapy, are included. Physicians caring for thalassemia patients have an increasing variety of treatment options available. Future clinical studies will determine the place of newer agents and modalities in improving the quality of life as well as the life expectancy of thalassemia patients.

Pathophysiology of thalassaemia

Most of the major clinical manifestations of the beta-thalassaemias can be related to the deleterious effects of imbalanced globin chain synthesis on erythroid maturation and red cell survival. The destruction of red cell progenitors and their progeny results from an extremely complex series of mechanisms all related to the presence of excess alpha-globin chain production. These include mechanical damage, interference with cell division and oxidative destruction of both organelles and components of the red cell membrane. The unequal distribution of gamma-globin chains between different precursors, and the intense selection of those with relatively higher levels of gamma chain production, lead to an extremely heterogeneous cell population in the peripheral blood. Iron overload, due to increased gastrointestinal absorption and blood transfusion is the major cause of tissue damage, morbidity and death.