High incidence of silent cerebral infarcts in adult patients with beta thalassemia major

Hypercoagulability in hemoglobinopathies: Decoding the thrombotic threat

Beta (β)-thalassemia and sickle cell disease (SCD) are characterized by a hypercoagulable state, which can significantly influence organ complication and disease severity. While red blood cells (RBCs) and erythroblasts continue to play a central role in the pathogenesis of thrombosis in β-thalassemia and SCD, additional factors such as free heme, inflammatory vasculopathy, splenectomy, among other factors further contribute to the complexity of thrombotic risk. Thus, understanding the role of the numerous factors driving this hypercoagulable state will enable healthcare practitioners to enhance preventive and treatment strategies and develop novel therapies for the future. We herein describe the pathogenesis of thrombosis in patients with β-thalassemia and SCD. We also identify common mechanisms underlying the procoagulant profile of hemoglobinopathies translating into thrombotic events. Finally, we review the currently available prevention and clinical management of thrombosis in these patient populations.

Cognitive impairment and hippocampal neuronal damage in β-thalassaemia mice

β-Thalassaemia is one of the most common genetic diseases worldwide. During the past few decades, life expectancy of patients has increased significantly owing to advance in medical treatments. Cognitive impairment, once has been neglected, has gradually become more documented. Cognitive impairment in β-thalassaemia patients is associated with natural history of the disease and socioeconomic factors. Herein, to determined effect of β-thalassaemia intrinsic factors, 22-month-old β-thalassaemia mouse was used as a model to assess cognitive impairment and to investigate any aberrant brain pathology in β-thalassaemia. Open field test showed that β-thalassaemia mice had decreased motor function. However, no difference of neuronal degeneration in primary motor cortex, layer 2/3 area was found. Interestingly, impaired learning and memory function accessed by a Morris water maze test was observed and correlated with a reduced number of living pyramidal neurons in hippocampus at the CA3 region in β-thalassaemia mice. Cognitive impairment in β-thalassaemia mice was significantly correlated with several intrinsic β-thalassaemic factors including iron overload, anaemia, damaged red blood cells (RBCs), phosphatidylserine (PS)-exposed RBC large extracellular vesicles (EVs) and PS-exposed medium EVs. This highlights the importance of blood transfusion and iron chelation in β-thalassaemia patients. In addition, to improve patients' quality of life, assessment of cognitive functions should become part of routine follow-up.

Modified Magnetic Resonance Imaging Burden of Cerebral Small Vessel Disease and Related Risk Factors in Patients With Thalassemia

OBJECTIVE

This study aimed to explore the burden of magnetic resonance imaging (MRI) of cerebral small vessel disease (CSVD) in patients with thalassemia and related risk factors.

METHODS

The clinical data and MRI of patients with thalassemia were retrospectively analyzed, and non-thalassemia controls with matched sex and age were selected. The modified MRI burden of CSVD included recent small subcortical infarct, presumed vasogenic white matter hyperintensity, presumed vasogenic lacunae, perivascular space (PVS), and brain atrophy.

RESULTS

This study included 110 patients in each of the thalassemia and control groups. There was no significant difference in sex, age, and common cerebrovascular disease risk factors between the 2 groups. The patients with thalassemia had a higher red blood cell count and lower content of hemoglobin. The PVS and modified MRI burden scores in the thalassemia group were higher than in the control group. With the increase in age, patients with thalassemia have a more severe CSVD burden.

CONCLUSION

Patients with thalassemia have a heavier modified MRI burden of CSVD than non-thalassemia patients, particularly PVS, and aging is an important risk factor for CSVD changes.

Pathogenic Mechanisms in Thalassemia I: Ineffective Erythropoiesis and Hypercoagulability

Erythropoiesis is the physiological process that results in the production of red blood cells (RBCs). In conditions of pathologically altered erythropoiesis or ineffective erythropoiesis, as in the case of β-thalassemia, the reduced ability of erythrocytes to differentiate, survive and deliver oxygen stimulates a state of stress that leads to the ineffective production of RBCs. We herein describe the main features of erythropoiesis and its regulation in addition to the mechanisms behind ineffective erythropoiesis development in β-thalassemia. Finally, we review the pathophysiology of hypercoagulability and vascular disease development in β-thalassemia and the currently available prevention and treatment modalities.

Hemorheological profiles and chronic inflammation markers in transfusion-dependent and non-transfusion- dependent thalassemia

The rheological properties of blood play an important role in regulating blood flow in micro and macro circulation. In thalassemia syndromes red blood cells exhibit altered hemodynamic properties that facilitate microcirculatory diseases: increased aggregation and reduced deformability, as well as a marked increase in adherence to the vascular endothelial cells. A personalized approach to treating thalassemia patients (transfusions, iron chelation, and splenectomy), has increased patients' life expectancy, however they generally present many complications and several studies have demonstrated the presence of high incidence of thromboembolic events. In this study the hemorheological profiles of thalassemia patients have been characterized to point out new indices of vascular impairment in thalassemia. Plasma viscosity, blood viscosities at low and high shear rates (η1 and η200, respectively), erythrocyte aggregation index (η1/η200), and the erythrocyte viscoelastic profile (elastic modulus G', and viscous modulus G") have been studied in transfusion-dependent and non-transfusion-dependent thalassemia patients. Moreover, the levels of inflammation biomarkers in thalassemia have been evaluated to investigate a relationship between the biomarkers, the disease severity and the rheological parameters. The biomarkers studied are the main components of the immune and endothelial systems or are related to vascular inflammation: cytokines (IL-2, IL-6, IL-10, IL-17A, TNF-alpha), chemokines (IL-8, MIP-1alpha), adipocytokines (leptin and adiponectin), growth factors (VEGF, angiopoietin-1), adhesion molecules (ICAM-1, VCAM-1, E-selectin, L-selectin), and a monocyte/macrophage activation marker (CD163). This study shows that transfusion-dependent thalassemia patients, both major and intermedia, have blood viscosities comparable to those of healthy subjects. Non-transfusion-dependent thalassemia intermedia patients show high blood viscosities at low shear rates (η1), corresponding to the flow conditions of the microcirculation, an increase in erythrocyte aggregation, and high values of the elastic G' and viscous G" modules that reflect a reduced erythrocyte deformability and an increase in blood viscosity. Levels of cytokines, chemokines and adhesion molecules are different in transfusion- and non-transfusion dependent patients and positive correlations between η1 or η1/η200 and the cytokines IL-6 and IL-10 have been observed. The evaluation of the hemorheological profiles in thalassemia can provide new indicators of vascular impairment and disease severity in thalassemia in order to prevent the onset of thromboembolic events.

The clinical characteristics of acute cerebral infarction patients with thalassemia in a tropic area in China

This study aimed to explore the clinical characteristics of acute cerebral infarction (ACI) patients with thalassemia through the analysis of clinical data. Adult patients with ACI who were admitted to the First Affiliated Hospital of Hainan Medical College, the Second Affiliated Hospital of Hainan Medical College, Hainan Provincial People's Hospital, and the Department of Neurology of Haikou People's Hospital from January 2008 to December 2018 were enrolled. According to the eligibility criteria, 183 ACI patients were examined, of whom there were 33 cases with thalassemia, 50 cases with iron-deficiency anemia (IDA), and 100 non-anemic cases. Laboratory data, including platelet count, homocysteine count, and hemoglobin level, were collected. Besides, the results of auxiliary examinations, such as brain magnetic resonance imaging or computed tomography, carotid ultrasound, electrocardiogram, and cardiac color ultrasound, were collected. Baseline clinical data (e.g., history of smoking and drinking) were acquired. The clinical characteristics were compared and analyzed among the three groups. There were more female ACI patients with thalassemia than male ones. Furthermore, lesions in the thalassemia and IDA groups were mainly located in the region from the corona radiata and the centrum semiovale, in which multiple small infarcts were dominant. In the non-anemia group, patients' lesions were mainly found in the basal ganglia area, and single small infarcts had the highest proportion.

Cognitive Impairment in Thalassemia and Associated Factors

INTRODUCTION

Patients with thalassemia increase the risk of developing cognitive impairment. Chronic anemia, oxidative stress from excess iron, and hypercoagulable state were related to this condition. The study regarding its prevalence and the associated factor in Southeast Asia is limited. Therefore, the study aimed to investigate the prevalence of cognitive impairment and associated factors.

METHODS

This was a cross-sectional study of thalassemic patients aged 18 years or more at the Hematology Clinic of Srinagarind Hospital, Khon Kaen University, Thailand, from January to May 2021. The Thai version of the Mini-Cog test was used to determine the presence of cognitive impairment. The clinical and laboratory parameters indicated as potential risk factors for dementia were evaluated in all patients. A stepwise logistic regression analysis was used to determine the associated risk factors for cognitive impairment.

RESULTS

Among 150 patients, cognitive impairment was found in 40 patients (26.7%). Age per 10-year increase (adjusted odds ratio [AOR] of 1.6), no iron chelation therapy (AOR of 9.8), current smoking (AOR of 5.0), hemoglobin (Hb) (AOR of 0.63), and ferritin (AOR of 1.0001) were independent factors associated with cognitive impairment.

CONCLUSIONS

The prevalence of cognitive impairment was high among thalassemic patients. Increasing age, low Hb, iron overload, and current smoking were significant associated factors with cognitive impairment. Screening for dementia in these patients is recommended, particularly in patients with high-risk factors.

Cerebral oxygen metabolic stress is increased in children with sickle cell anemia compared to anemic controls

Patients with sickle cell anemia (SCA) experience cerebral metabolic stress with an increase in oxygen extraction fraction (OEF) to compensate for reduced oxygen carrying capacity due to anemia. It remains unclear if anemia alone drives this metabolic stress. Using MRI, we collected voxel-wise OEF measurements to test our hypothesis that OEF would be elevated in anemic controls without SCA (AC) compared to healthy controls (HC), but OEF would be even higher in SCA compared to AC. Brain MRIs (N = 159) were obtained in 120 participants (34 HC, 27 AC, 59 SCA). While hemoglobin was lower in AC versus HC (p < 0.001), hemoglobin was not different between AC and SCA cohorts (p = 0.459). Whole brain OEF was higher in AC compared to HC (p < 0.001), but lower compared to SCA (p = 0.001). Whole brain OEF remained significantly higher in SCA compared to HC (p = 0.001) while there was no longer a difference between AC versus HC (p = 0.935) in a multivariate model controlling for age and hemoglobin. OEF peaked within the border zone regions of the brain in both SCA and AC cohorts, but the volume of white matter with regionally elevated OEF in AC was smaller (1.8%) than SCA (58.0%). While infarcts colocalized within regions of elevated OEF, more SCA participants had infarcts than AC (p < 0.001). We conclude that children with SCA experience elevated OEF compared to AC and HC after controlling for the impact of anemia, suggesting that there are other pathophysiologic factors besides anemia contributing to cerebral metabolic stress in children with SCA.

Moyamoya syndrome in a child with HbEβ-thalassemia

Moyamoya is a progressive cerebrovascular disease associated with stenosis or occlusion of the arteries of the Circle of Willis. It is uncommon in thalassemia. We present a 9-year-old girl with HbEβ-thalassemia who presented with headache, vomiting, and episodes of transient hemiparesis with complete occlusion internal carotid arteries.

Asymptomatic intracranial aneurysms in beta-thalassemia: a three-year follow-up report

Background

No information is currently available regarding the natural history of asymptomatic intracranial aneurysms in beta-thalassemia, raising several concerns about their proper management.

Methods

We performed a prospective longitudinal three-year-long MR-angiography study on nine beta-thalassemia patients (mean-age 40.3 ± 7.5, six females, 8 transfusion dependent) harboring ten asymptomatic intracranial aneurysms. In addition, we analyzed the clinical files of all adult beta-thalassemia patients (160 patients including those followed with MR-angiography, 121 transfusion dependent) referring to our Centers between 2014 and 2019 searching for history of subarachnoid hemorrhage or history of symptomatic intracranial aneurysms.

Results

At the end of the three-year-long follow-up, no patient showed any change in the size and shape of the aneurysms, none presented new intracranial aneurysms or artery stenoses, none showed new brain vascular-like parenchymal lesions or enlargement of the preexisting ones. Besides, in our database of all adult beta-thalassemia patients, no one had history of subarachnoid hemorrhage or history of symptomatic intracranial aneurysms.

Conclusions

Incidental asymptomatic intracranial aneurysms do not seem to be associated, in beta-thalassemia, with an increased risk of complications (enlargement or rupture) at least in the short term period, helping to optimize human and economic resources and patient compliance during their complex long-lasting management.

Anemia predicts lower white matter volume and cognitive performance in sickle and non-sickle cell anemia syndrome

Severe chronic anemia is an independent predictor of overt stroke, white matter damage, and cognitive dysfunction in the elderly. Severe anemia also predisposes to white matter strokes in young children, independent of the anemia subtype. We previously demonstrated symmetrically decreased white matter (WM) volumes in patients with sickle cell disease (SCD). In the current study, we investigated whether patients with non-sickle anemia also have lower WM volumes and cognitive dysfunction. Magnetic Resonance Imaging was performed on 52 clinically asymptomatic SCD patients (age = 21.4 ± 7.7; F = 27, M = 25; hemoglobin = 9.6 ± 1.6 g/dL), 26 non-sickle anemic patients (age = 23.9 ± 7.9; F = 14, M = 12; hemoglobin = 10.8 ± 2.5 g/dL) and 40 control subjects (age = 27.7 ± 11.3; F = 28, M = 12; hemoglobin = 13.4 ± 1.3 g/dL). Voxel-wise changes in WM brain volumes were compared to hemoglobin levels to identify brain regions that are vulnerable to anemia. White matter volume was diffusely lower in deep, watershed areas proportionally to anemia severity. After controlling for age, sex, and hemoglobin level, brain volumes were independent of disease. WM volume loss was associated with lower Full Scale Intelligence Quotient (FSIQ; P = .0048; r² = .18) and an abnormal burden of silent cerebral infarctions (P = .029) in males, but not in females. Hemoglobin count and cognitive measures were similar between subjects with and without white-matter hyperintensities. The spatial distribution of volume loss suggests chronic hypoxic cerebrovascular injury, despite compensatory hyperemia. Neurocognitive consequences of WM volume changes and silent cerebral infarction were strongly sexually dimorphic. Understanding the possible neurological consequences of chronic anemia may help inform our current clinical practices.

Attention, response inhibition and brain event-related potential alterations in adults with beta-thalassaemia major

We investigated neural correlates of cognitive function in adults with beta thalassaemia major (β-TM) compared to healthy controls using scalp-recorded event-related potentials (ERPs). Event-related potential studies in the field of β-TM are scarce and mostly limited to children. A stop-signal task was used to evaluate indices of attention and response inhibition function, considered to be the hallmark of executive control. Correlations between task performance, ERPs and haemoglobin were also examined. Results showed impaired cognitive performance in β-TM patients, as indicated by longer response times than controls. Haemoglobin was negatively correlated with response times to Go stimuli. Electrophysiological results indicated significant β-TM-related alterations in neuronal activity, reflected in greater peak amplitudes of several task-related ERP components. A possible interpretation of these ERP results is that β-TM patients need to recruit additional brain resources when dealing with cognitive challenge. Significant correlations were found between levels of haemoglobin and amplitude of all ERP components; the lower the haemoglobin, the more pronounced the ERPs amplitude. The present study represents a novel investigation of cognitive function and related brain dynamics in β-TM in adult. Integrating neuropsychological assessment and interventions into traditional disease management, may be imperative in achieving a better quality of life for these patients.

No increased cerebrovascular involvement in adult beta-thalassemia by advanced MRI analyses

Beta-thalassemia-related anemia and chronic hypercoagulative state are supposed to cause cumulative cerebrovascular damage with consequent parenchymal/vascular changes and functional impairment. However, recent conventional MRI/MR-angiography investigations failed to show an increased cerebrovascular involvement in beta-thalassemia patients managed according to current treatment guidelines, in spite of significantly decreased full-scale IQ scores. We therefore investigated those patients and controls by means of advanced quantitative MRI analyses (based on magnetization transfer and diffusion tensor imaging) searching for signs of possible cerebrovascular injuries undetected by conventional MRI/MR-angiography. The 3 T-MRI study protocol included diffusion tensor imaging and 3D-multi-echo FLASH sequences for magnetization transfer analysis. Whole-brain voxel-based analyses showed that magnetization transfer, fractional anisotropy, and mean, radial and axial diffusivity do not differ between healthy controls and beta-thalassemia patients (considered as a whole group or as distinct transfusion dependent and non-transfusion dependent subgroups). No correlation emerged between all the considered MRI metrics and cognitive findings (full-scale IQ) or the main clinical and laboratory data. According to our findings, adult neurologically-asymptomatic beta-thalassemia patients (regardless of clinical severity) do not seem to present an increased disease-related cerebrovascular vulnerability compared to healthy controls downsizing the need of regular brain MRI monitoring, at least when the current treatment guidelines are followed.

No evidence of increased cerebrovascular involvement in adult neurologically-asymptomatic β-Thalassaemia. A multicentre multimodal magnetic resonance study

Multi-factorial causes jeopardize brain integrity in β-thalassaemia. Intracranial parenchymal and vascular changes have been reported among young β-thalassaemia patients but conventional magnetic resonance imaging (MRI) findings are contradictory making early MRI and magnetic resonance angiography (MRA)/venography monitoring a matter of debate. This study prospectively investigated 75 neurologically asymptomatic β-thalassaemia patients (mean-age 35·2 ± 10·7 years; 52/75 transfusion-dependent; 41/75 splenectomised) using a 3T magnetic resonance scanner; clinical, laboratory and treatment data were also collected. White matter ischaemic-like abnormalities, intracranial artery stenoses, aneurysms and sinus venous thrombosis were compared between patients and 56 healthy controls (mean-age 33·9 ± 10·8 years). No patient or control showed silent territorial or lacunar strokes, intracranial artery stenoses or signs of sinus thrombosis. White matter lesions were found both in patients (35/75, 46·7%) and controls (28/56, 50·0%), without differences in terms of number (4·0 ± 10·6 vs. 4·6 ± 9·1, P = 0·63), size and Fazekas' Score. Intracranial aneurysms did not differ between patients and controls for incidence rate (7/75, 9·3% vs. 5/56, 8·9%), size and site. Vascular and parenchymal abnormality rate did not differ according to treatments or clinical phenotype. According to this study, asymptomatic β-thalassaemia patients treated according to current guidelines do not seem to carry an increased risk of brain and intracranial vascular changes, thus weakening recommendations for regular brain MRI monitoring.

Microparticles from β-thalassaemia/HbE patients induce endothelial cell dysfunction

Thromboembolic complication occurs frequently in β-thalassaemia/HbE patients, particularly in splenectomised patients. Endothelial cells play an important role in thrombosis. There is strong evidence of endothelial cell activation and dysfunction in β-thalassaemia. Microparticles (MPs) are associated with thrombosis and endothelial cell dysfunction in many diseases including β-thalassaemia. However, the effect of thalassaemic-MPs on endothelial cells mediating thrombus formation has not been elucidated. In this study, the effects of circulating MPs from β-thalassaemia/HbE patients on endothelial cell functions were investigated. The results showed that MPs directly induce tissue factor, interleukin (IL)-6, IL-8, intracellular adhesion molecule-1, vascular cell adhesion molecule-1 and E-selectin expression in human umbilical vein endothelial cells (HUVECs). Notably, the levels of these endothelial cell activation markers were significantly increased in HUVECs treated with MPs obtained from splenectomised β-thalassaemia/HbE patients when compared to MPs from non-splenectomised patients or normal subjects. The increased endothelial cell activation ultimately lead to increased monocyte-endothelial cell adhesion. THP-1 and HUVECs adhesion induced by MPs from normal subjects, non-splenectomised and splenectomised patients increased to 2.0 ± 0.4, 2.3 ± 0.4 and 3.8 ± 0.4 fold, respectively when compared to untreated cells. This finding suggests that MPs play an important role on thrombosis and vascular dysfunction in β-thalassaemia/HbE disease, especially in splenectomised cases.

Disturbed Red Blood Cell Structure and Function: An Exploration of the Role of Red Blood Cells in Neurodegeneration

The structure of red blood cells is affected by many inborn and acquired factors, but in most cases this does not seem to affect their function or survival in physiological conditions. Often, functional deficits become apparent only when they are subjected to biochemical or mechanical stress in vitro, or to pathological conditions in vivo. Our data on the misshapen red blood cells of patients with neuroacanthocytosis illustrate this general mechanism: an abnormal morphology is associated with an increase in the susceptibility of red blood cells to osmotic and mechanical stress, and alters their rheological properties. The underlying mutations may not only affect red cell function, but also render neurons in specific brain areas more susceptible to a concomitant reduction in oxygen supply. Through this mechanism, an increased susceptibility of already compromised red blood cells to physiological stress conditions may constitute an additional risk factor in vulnerable individuals. Also, susceptibility may be induced or enhanced by systemic pathological conditions such as inflammation. An exploration of the literature suggests that disturbed red blood cell function may play a role in the pathophysiology of various neurodegenerative diseases. Therefore, interventions that reduce the susceptibility of red blood cells to physiological and pathological stress may reduce the extent or progress of neurodegeneration.

Circulating microparticles and the risk of thromboembolic events in Egyptian beta thalassemia patients

The presence of elevated numbers of circulating microparticles (MPs) has been hypothesized to be responsible for the occurrence of thromboembolic events (TEEs) in thalassemic patients. Our aim is to evaluate the presence and the thrombotic risk of circulating MPs in thalassemia patients and to determine the difference in MPs between β-thalassemia major (β-TM) and thalassemia intermedia (TI). The percentage of the annexin-labeled MPs, platelet-derived MPs (PMPs), erythrocyte-derived MPs (RMPs), and endothelial-derived MPs (EMPs) was measured by flow cytometry, in 87 thalassemia patients (39 β-TM and 48 TI). By multiple regression analysis, we then assessed the various independent risk factors for the occurrence of TEE. The thalassemic patients who experienced TEE had a significantly higher platelet count, higher percentage of annexin-labeled MPs, and higher percentage of PMPs (p value = 0.014, 0.003, and 0.014, respectively). There was no significant difference between β-TM and TI patients at the level of any of the studied MPs. The predictive risk factors for TEE in thalassemic patients were splenectomy, total and direct bilirubin, the RMPs, and the EMPs (OR = 10.07 (CI = 3.7-27.1), 4.3 (CI = 2.1-8.7), 1.4 (CI = 1.5-6.2), 1.6 (CI = 1.1-2.2), 3.0 (CI = 1.9-4.9), respectively). In conclusion, the elevated numbers of circulating MPs is a risk factor for the TEE in thalassemia patients.