Cardiovascular magnetic resonance (CMR) and hepatic magnetic resonance imaging (MRI) has become a reliable non-invasive tool to monitor iron excess in thalassemia major (TM) patients. However, long-term studies are lacking. We reviewed CMR and hepatic MRI T2* imaging on 54 TM patients who had three or more annual measurements. They were managed on various chelation regimens. Patients were grouped according to their degree of cardiac siderosis: severe (T2*<10msec), mild to moderate (T2*=10-20 msec) and no cardiac siderosis (T2*>20msec). We looked at the change in cardiac T2*, liver iron concentration (LIC) and left ventricular ejection fraction (LVEF) at years 3 and 5. In patients with severe cardiac siderosis, cardiac T2* (mean±SD) improved from 6.9±1.6 at baseline to 13.6±10.0 by year 5, mean ΔT2*=6.7 (p-value 0.04). Change in cardiac T2* at year 3 was not significant in the severe group. Patients with mild to moderate cardiac siderosis had mean cardiac T2* of 14.6±2.9 at baseline which improved to 26.3±9.5 by year 3, mean ΔT2*=11.7 (p-value 0.01). At baseline, median LIC (mg/gm dw) in patients with severe, mild-moderate and no cardiac siderosis was 3.6, 2.8 and 3.3 while LVEF (mean±SD) (%) was 56.3±10.1, 60±5 and 66±7.6 respectively. No significant correlation was noted between Δ cardiac T2* and Δ LIC, Δ cardiac T2* and Δ LVEF at years 3 and 5. Throughout the observation period, patients with no cardiac siderosis maintained their cardiac T2* above 20msec. The majority of patients with cardiac siderosis improve cardiac T2* over time with optimal chelation.
thalassemia; cardiac siderosis; chelation
Hemoglobin H-constant spring (Hb H-CS), the most common nondeletional alpha
thalassemia in Asia is increasingly recognized in North America due to shifts in
immigration patterns. In California, alpha (α)-thalassemia syndromes are the second
most frequent finding among newborns screened for hemoglobinopathies with a two-fold
increase compared to a decade earlier [1,2]. Though known to have a more severe anemia than Hb H
disease, the other clinical findings of Hb H-CS are not well described. Moreover,
beneficial therapies that have become available in the last decade are often not applied
to their care. This analysis of 46 patients enrolled in the Thalassemia Clinical Research
Network (TCRN) age 13+/− 10 years old, with Hb H-CS revealed moderate anemia (mean
8.7 ± 1.5 g/dl), regular transfusion therapy in 24% of patients, and splenomegaly
or prior splenectomy in one-third of them. Serum transferin receptor (sTfr), was elevated;
(44.4 ± 18 mcg/ml normal range 2.9–8.3 mcg/ml), reflecting ineffective
erythropoiesis, which in turn leads to high iron absorption and increased ferritin levels
in younger (median = 187 ng/ml) and older (median = 465 ng/ml) nontransfused patients.
These findings along with moderate growth delay and low bone mass were more prevalent in
Hb H-CS patients compared to deletional Hb H disease. Our results highlight the required
monitoring of the extent of anemia, growth, splenomegaly, iron overload, gallstones, bone
density and assessment of need for transfusions and specific treatments for disease
Thalassemia is an inherited blood disorder that requires lifelong adherence to a complicated and burdensome medical regimen which could potentially impact emotional functioning of patients. The importance of understanding and promoting healthy emotional functioning is crucial not only to psychological well-being, but also to physical health as it has been shown to impact adherence to medical regimens [1–4]. The current study aimed to  determine the prevalence of depressive and anxiety symptoms in adolescent and adult patients with thalassemia; and  explore possible demographic, medical, and psychosocial correlates of these symptoms in 276 patients (14–58 years old, M age = 27.83; 52% female). Overall, most patients did not report experiencing significant symptoms of anxiety and depression (33% of participants indicated experiencing symptoms of anxiety and 11% symptoms of depression). Females and older patients were more likely to experience these symptoms than males and younger patients. Symptoms of anxiety and depression were positively associated with self-report of difficulty with adherence and negatively associated with quality of life. Given these findings, regular screening for anxiety and depression symptoms could help to identify at-risk individuals to provide them with appropriate psychological support with the goal of improving both emotional and physical health.
Little is known about the effects of thalassaemia on the kidney. Characterization of underlying renal function abnormalities in thalassaemia is timely because the newer iron chelator, deferasirox, can be nephrotoxic. We aimed to determine the prevalence and correlates of renal abnormalities in thalassaemia patients, treated before deferasirox was widely available, using 24-h collections of urine. We calculated creatinine clearance and urine calcium-to-creatinine ratio and measured urinary β2-microglobulin, albumin, and protein. We used multivariate modelling to identify clinical, therapeutic, and laboratory predictors of renal dysfunction. One-third of thalassaemia patients who were not regularly transfused had abnormally high creatinine clearance. Regular transfusions were associated with a decrease in clearance (P = 0·004). Almost one-third of patients with thalassaemia had hypercalciuria, and regular transfusions were associated with an increase in the frequency and degree of hypercalciuria (P < 0·0001). Albuminuria was found in over half of patients, but was not consistently associated with transfusion therapy. In summary, renal hyperfiltration, hypercalciuria, and albuminuria are common in thalassaemia. Higher transfusion intensity is associated with lower creatinine clearance but more frequent hypercalciuria. The transfusion effect needs to be better understood. Awareness of underlying renal dysfunction in thalassaemia can inform decisions now about the use and monitoring of iron chelation.
thalassaemia; kidney; creatinine clearance; hyperfiltration; hypercalciuria; albuminuria; proteinuria; transfusion
Hydroxyurea (HU) is highly effective treatment for Sickle Cell Disease (SCD). While pediatric use of HU is accepted clinical practice, barriers to use may impede its potential benefit.
A survey of parents of children ages 5–17 years with SCD was performed across five institutions to assess factors associated with HU use.
Of the 173 parent responses, 65 (38%) had children currently taking HU. Among parents of children not taking HU, the most commonly cited reasons were that their hematology provider had not offered it, their child was not sufficiently symptomatic and concerns about potential side effects. Even parents of HU users reported widespread concern about effectiveness, long-term safety and off-label use. In bivariate analyses, children’s ages, parental demographics such as education level, or travel time to their hematology provider were not correlated with HU use. Bivariate analysis and multivariate logistic regression revealed three significant factors associated with current HU use: better parental knowledge about its major therapeutic effects (p<0.001), sickle genotype (p=0.005) and institution of clinical care (p=0.04).
Pervasive concerns about HU safety exist, even among parents of current users. Varying knowledge among parents appears to be independent of their demographics, and is associated with HU use. Inter-institutional variability in parental knowledge and drug uptake highlights potentially potent site-specific influences on likelihood of HU use. Overall, these survey data underscore the need for strategies to bolster parental understanding about benefits of HU and address concerns about its safety.
Hydroxyurea; sickle cell disease; knowledge; and barriers; outcomes research
Regulation of erythropoiesis is achieved by integration of distinct signals. Among these, macrophages are emerging as erythropoietin-complementary regulators of erythroid development, particularly under stress conditions. We investigated the contribution of macrophages for physiological and pathological conditions of enhanced erythropoiesis. We utilized mouse models of induced anemia, Polycythemia vera and β-thalassemia in which macrophages were chemically depleted. Our data indicate that macrophages contribute decisively for recovery from induced anemia as well as the pathological progression of Polycythemia vera and β-thalassemia by modulating erythroid proliferation and differentiation. We validated these observations in primary human cultures, showing a critical direct impact of macrophages on proliferation and enucleation of erythroblasts from healthy individuals and Polycythemia vera or β-thalassemic patients. In summary, we identify a new mechanism that we named “Stress Erythropoiesis Macrophage-supporting Activity” (SEMA) that contributes to the pathophysiology of these disorders and will have critical scientific and therapeutic implications in the near future.
Hepcidin (HAMP) negatively regulates iron absorption, degrading the iron exporter ferroportin at the level of enterocytes and macrophages. We showed that mice with β-thalassemia intermedia (th3/+) have increased anemia and iron overload. However, their hepcidin expression is relatively low compared to their iron burden. We also showed that the iron metabolism gene Hfe is down-regulated in concert with hepcidin in th3/+ mice. These observations suggest that low hepcidin levels are responsible for abnormal iron absorption in thalassemic mice and that down-regulation of Hfe might be involved in the pathway that controls hepcidin synthesis in β-thalassemia. Therefore, these studies suggest that increasing hepcidin and/or Hfe expression could be a strategy to reduces iron overload in these animals. The goal of this paper is to review recent findings that correlate hepcidin, Hfe, and iron metabolism in β-thalassemia and to discuss potential novel therapeutic approaches based on these recent discoveries.
β-thalassemia; iron overload; hepcidin; Hfe; lentiviral vectors
Fetal hemoglobin level is a heritable complex trait that strongly correlates swith the clinical severity of sickle cell disease. Only few genetic loci have been identified as robustly associated with fetal hemoglobin in patients with sickle cell disease, primarily adults. The sole approved pharmacologic therapy for this disease is hydroxyurea, with effects largely attributable to induction of fetal hemoglobin.
In a multi-site observational analysis of children with sickle cell disease, candidate single nucleotide polymorphisms associated with baseline fetal hemoglobin levels in adult sickle cell disease were examined in children at baseline and induced by hydroxyurea therapy. For baseline levels, single marker analysis demonstrated significant association with BCL11A and the beta and epsilon globin loci (HBB and HBE, respectively), with an additive attributable variance from these loci of 23%. Among a subset of children on hydroxyurea, baseline fetal hemoglobin levels explained 33% of the variance in induced levels. The variant in HBE accounted for an additional 13% of the variance in induced levels, while variants in the HBB and BCL11A loci did not contribute beyond baseline levels.
These findings clarify the overlap between baseline and hydroxyurea-induced fetal hemoglobin levels in pediatric disease. Studies assessing influences of specific sequence variants in these and other genetic loci in larger populations and in unusual hydroxyurea responders are needed to further understand the maintenance and therapeutic induction of fetal hemoglobin in pediatric sickle cell disease.
Preclinical and clinical studies demonstrate the feasibility of treating β-thalassemia and Sickle Cell Disease (SCD) by lentiviral-mediated transfer of the human β-globin gene. However, previous studies have not addressed whether the ability of lentiviral vectors to increase hemoglobin synthesis might vary in different patients.
We generated lentiviral vectors carrying the human β-globin gene with and without an ankyrin insulator and compared their ability to induce hemoglobin synthesis in vitro and in thalassemic mice. We found that insertion of an ankyrin insulator leads to higher, potentially therapeutic levels of human β-globin through a novel mechanism that links the rate of transcription of the transgenic β-globin mRNA during erythroid differentiation with polysomal binding and efficient translation, as reported here for the first time. We also established a preclinical assay to test the ability of this novel vector to synthesize adult hemoglobin in erythroid precursors and in CD34+ cells isolated from patients affected by β-thalassemia and SCD. Among the thalassemic patients, we identified a subset of specimens in which hemoglobin production can be achieved using fewer copies of the vector integrated than in others. In SCD specimens the treatment with AnkT9W ameliorates erythropoiesis by increasing adult hemoglobin (Hb A) and concurrently reducing the sickling tetramer (Hb S).
Our results suggest two major findings. First, we discovered that for the purpose of expressing the β-globin gene the ankyrin element is particularly suitable. Second, our analysis of a large group of specimens from β-thalassemic and SCD patients indicates that clinical trials could benefit from a simple test to predict the relationship between the number of vector copies integrated and the total amount of hemoglobin produced in the erythroid cells of prospective patients. This approach would provide vital information to select the best candidates for these clinical trials, before patients undergo myeloablation and bone marrow transplant.
Advances in the management of thalassemia have resulted in increased life expectancy and new challenges. We conducted the first survey of education and employment status of people with thalassemia in North America.
A total of 633 patients (349 adults and 284 school age children) enrolled in the Thalassemia Clinical Research Network (TCRN) registry in Canada and the US were included in the data analysis. Predictors considered for analysis were age, gender, race/ethnicity, site of treatment (Canada vs. United States), transfusion and chelation status, serum ferritin, and clinical complications.
Seventy percent of adults were employed of which 67 percent reported working full-time. Sixty percent had a college degree and 14% had achieved some post college education. Eighty-two percent of school age children were at expected grade level. In a multivariate analysis for adults, Whites (OR=2.76, 95% CI: 1.50-5.06) were more likely to be employed compared to Asians. Higher education in adults was associated with older age (OR=1.67, 95% CI: 1.29-2.15), female gender (OR=2.08, 95% CI: 1.32-3.23) and absence of lung disease (OR=14.3, 95% CI: 2.04-100). Younger children (OR=5.7 for 10 year increments, 95% CI: 2.0 – 16.7) and Canadian patients (OR=5.6, 95% CI: 1.5-20) were more likely to be at the expected education level. Neither transfusion nor chelation was associated with lower employment or educational achievement.
Individuals with thalassemia in North America can achieve higher education; however, full-time employment remains a problem. Transfusion and chelation do not affect employment or education status of this patient population.
Employment; Education; Thalassemia
To measure body composition in patients with thalassemia and explore its relationship to abnormal growth and bone mass.
Cross-sectional, multi-center study. Fat, lean, and bone mineral density (BMD) were assessed by DXA. Medical history, food frequency and physical activity questionnaires were conducted in 257 transfused thalassemia patients (23.7 ± 11 yr, Mean±SD, 51% male) compared with 113 non-transfused patients (21.3 ± 13 yr, 44% male).
Subjects with thalassemia were leaner compared with healthy Americans from NHANES III data. Transfused subjects had higher percentage body fat compared with non- transfused after controlling for age, sex and ethnicity; 11.8% of non-transfused pediatric subjects were considered underweight, significantly lower than NHANES data (p=0.03). Hemoglobin level was positively related to lean mass (p=0.008). Body fat and lean mass were positive predictors for both height and BMD Z-scores after adjustment for transfusion status, age, sex, ethnicity, calcium intake and physical activity (all p<0.001).
Though the majority of adult patients with thalassemia had healthy body composition with rare obesity, young, non-transfused patients appear at risk for being underweight. Optimizing physical activity and appropriate use of transfusion therapy may improve growth and bone health in these at risk patients.
DXA; lean mass; fat mass; body mass index (BMI); calcium
Lentiviral-mediated β-globin gene transfer successfully treated β-thalassemic mice. Based on this result, clinical trials were initiated. To date, however, no study has investigated the efficacy of gene therapy in relation to the nature of the different β-globin mutations found in patients. Most mutations can be classified as β0 or β+, based on the amount of β-globin protein produced. Therefore, we propose that a screening in vitro is necessary to verify the efficacy of gene transfer prior to treatment of individual patients. We used a two-phase liquid culture system to expand and differentiate erythroid progenitor cells (ErPCs) transduced with lentiviral vectors. We propose the use of this system to test the efficiency of lentiviral vectors carrying the human β-globin gene, to correct the phenotype of ErPCs from patients preparing for gene therapy. This new approach might have profound implications for designing gene therapy and for understanding the genotype/phenotype variability observed in Cooley’s anemia patients.
β-thalassemia; β-globin; gene therapy; lentiviral vectors; hemoglobin; erythroid progenitor cells
Osteoporosis and fractures occur frequently in patients with beta thalassemias, a group of congenital hemolytic anemias characterized by decreased synthesis of the beta chain of hemoglobin. In this study, we determined the bone abnormalities of the th3 thalassemia mouse, generated by deletion of the mouse beta chain genes. The heterozygote th3/+ mouse has moderate anemia, and serves as a model of beta thalassemia intermedia (TI), which represents the mild thalassemia phenotype. The th3/th3 mouse has lethal anemia and is a model of beta thalassemia major (TM), which is characterized by life-threatening anemia requiring regular transfusions to sustain life.
Compared to controls: i) Micro-CT of trabecular bone showed decreased bone volume fraction, number of trabeculae and trabecular thickness in both th3/+ and th3/th3 (p<0.05). ii) Cortical bone analysis showed thinner cortices and increased marrow area in th3/+ animals (p<0.05). iii) Micro-CT abnormalities in th3/+ mice were present by 2 months and did not worsen with age. iv) Histomorphometry was significant for decreased bone formation and resorption in both th3/+ and th3/th3. Similarly, cathepsin K and osteocalcin expression from bone of both th3/+and th3/th3 animals was reduced (p<0.05). vi) Biomechanics showed reduced maximum load, maximum moment and structural stiffness in both th3/+and th3/th3 (p<0.01).
In conclusion, the th3 mouse model of thalassemia manifests bone changes reminiscent of those in humans, and can be used for further bone studies in thalassemia. Bone changes are associated with decreased bone turnover, and develop early on during the period of bone accrual.
Excessive iron absorption is one of the main features of β-thalassemia and can lead to severe morbidity and mortality. Serial analyses of β-thalassemic mice indicate that while hemoglobin levels decrease over time, the concentration of iron in the liver, spleen, and kidneys markedly increases. Iron overload is associated with low levels of hepcidin, a peptide that regulates iron metabolism by triggering degradation of ferroportin, an iron-transport protein localized on absorptive enterocytes as well as hepatocytes and macrophages. Patients with β-thalassemia also have low hepcidin levels. These observations led us to hypothesize that more iron is absorbed in β-thalassemia than is required for erythropoiesis and that increasing the concentration of hepcidin in the body of such patients might be therapeutic, limiting iron overload. Here we demonstrate that a moderate increase in expression of hepcidin in β-thalassemic mice limits iron overload, decreases formation of insoluble membrane-bound globins and reactive oxygen species, and improves anemia. Mice with increased hepcidin expression also demonstrated an increase in the lifespan of their red cells, reversal of ineffective erythropoiesis and splenomegaly, and an increase in total hemoglobin levels. These data led us to suggest that therapeutics that could increase hepcidin levels or act as hepcidin agonists might help treat the abnormal iron absorption in individuals with β-thalassemia and related disorders.
Adults with β thalassemia major frequently have low BMD, fractures, and bone pain. The purpose of this study was to determine the prevalence of low BMD, fractures, and bone pain in all thalassemia syndromes in childhood, adolescence, and adulthood, associations of BMD with fractures and bone pain, and etiology of bone disease in thalassemia. Patients of all thalassemia syndromes in the Thalassemia Clinical Research Network, ≥6 yr of age, with no preexisting medical condition affecting bone mass or requiring steroids, participated. We measured spine and femur BMD and whole body BMC by DXA and assessed vertebral abnormalities by morphometric X-ray absorptiometry (MXA). Medical history by interview and review of medical records, physical examinations, and blood and urine collections were performed. Three hundred sixty-one subjects, 49% male, with a mean age of 23.2 yr (range, 6.1–75 yr), were studied. Spine and femur BMD Z-scores < −2 occurred in 46% and 25% of participants, respectively. Greater age, lower weight, hypogonadism, and increased bone turnover were strong independent predictors of low bone mass regardless of thalassemia syndrome. Peak bone mass was suboptimal. Thirty-six percent of patients had a history of fractures, and 34% reported bone pain. BMD was negatively associated with fractures but not with bone pain. Nine percent of participants had uniformly decreased height of several vertebrae by MXA, which was associated with the use of iron chelator deferoxamine before 6 yr of age. In patients with thalassemia, low BMD and fractures occur frequently and independently of the particular syndrome. Peak bone mass is suboptimal. Low BMD is associated with hypogonadism, increased bone turnover, and an increased risk for fractures.
DXA; BMD; fractures; vertebral morphometry; thalassemia