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During investigations of the phenotypic diversity of hemoglobin (Hb) E β thalassemia, a patient was encountered with persistently high levels of methemoglobin associated with a left-shift in the oxygen dissociation curve, profound ascorbate deficiency, and clinical features of scurvy; these abnormalities were corrected by treatment with vitamin C. Studies of erythropoietin production before and after treatment suggested that, as in an ascorbate-deficient murine model, the human hypoxia induction factor pathway is not totally dependent on ascorbate levels. A follow-up study of 45 patients with HbE β thalassemia showed that methemoglobin levels were significantly increased and that there was also a significant reduction in plasma ascorbate levels. Haptoglobin levels were significantly reduced, and the high frequency of the 2.2 haptoglobin genotype may place an additional pressure on ascorbate as a free-radical scavenger in this population. There was, in addition, a highly significant correlation between methemoglobin levels, splenectomy, and factors that modify the degree of globin-chain imbalance. Because methemoglobin levels are modified by several mechanisms and may play a role in both adaptation to anemia and vascular damage, there is a strong case for its further study in other forms of thalassemia and sickle-cell anemia, particularly when splenic function is defective.

Hemoglobin E β thalassemia is the commonest form of severe thalassemia in many Asian countries. Its remarkably variable clinical phenotype presents a major challenge to determining its most appropriate management. In particular, it is not clear why some patients with this condition can develop and function well at very low hemoglobin levels. Here, we demonstrate that patients with hemoglobin Eβ thalassemia have a significant decrease in the oxygen affinity of their hemoglobin, that is an increased P50 value, in response to anemia. This may in part reflect the lower level of hemoglobin F in this condition compared with other forms of β thalassemia intermedia. The ability to right-shift the oxygen dissociation curve was retained across the spectrum of mild and severe phenotypes, despite the significantly higher levels of hemoglobin F in the former, suggesting that efforts directed at producing a modest increase in the level of hemoglobin F in symptomatic patients with this disease should be of therapeutic value.

Introduction Worldwide the greatest burden of disease related to beta thalassemia resides in Asia and is largely represented by Hemoglobin E beta thalassemia (HbE/thal) [Weatherall DJ, Ann New York Acad Sci 2005, 1054:11-17]. HbE/thal is the most common serious form of beta thalassemia in many Asian populations. In Sri Lanka, over 17 years, we have characterized over 200 affected patients and had proposed [Olivieri, NF, et al., J Pediatr Hematol Oncol, 2000, 22:593-597], as now shown in less common forms of non-transfusion dependent thalassemia [Taher AT, et al., Br J Haematol 2010, 150:486-489], that non-transfusional iron accumulation (NTIA) is a potential complication in non-transfused patients with HbE/thal. In 2009, we implemented R2-MRI [St Pierre, TG, et al., Blood 2005, 105:855-861] in Sri Lanka. Here we report the variation and severity of non-transfusional iron accumulation (NTIA), in parallel with screening tests of organ dysfunction, in a first group of patients with HbE/thal. Methods Patients aged > 7 years with clinical evidence of iron overload (generally a serum ferritin > normal range in the absence of a history of regular transfusions) were recruited from The National Thalassaemia Centre (NTC), Kurunegala, Sri Lanka. LIC was measured using R2-MRI (FerriScan¨) with facilities situated a 6 hour return bus trip from the NTC. Liver function was evaluated using serum alanine transaminase (ALT). Fasting blood glucose (FBG), thyroid stimulating hormone (TSH), serum calcium and phosphate and serum ferritin (SF) were measured in local laboratories. Cardiac function was measured using echocardiography. Correlations between parameters were assessed using non-parametric (Spearman) analysis. Receiver operating characteristic (ROC) curve analysis was used to determine the optimum cut-off values of LIC and serum ferritin for predicting ALT values above the upper limit of the laboratory reference range. Results LIC measurements were successfully acquired for 110 of 112 enrolled subjects (45 male/ 67 female) with median age [range] 22.5 [7.8 – 61.5] years over 3 years. The variation in LIC was considerably, and unexpectedly, broad: median [range] LIC was 8.8 [0.7 – 65.0] mg Fe/g dw. LIC exceeded the threshold of risk established as 7.0 mg Fe/g dw [Olivieri NF, Brittenham GM, Blood 1997, 89:739-761] in a substantial proportion (57%) of patients. In parallel, organ dysfunction was observed: in a substantial group (52%), ALT was increased above normal range, while in 11%, ejection fraction was reduced (less than 56%). FBG and TSH were elevated above normal range in a substantial proportion of patients (6% and 30% respectively). Significant correlations were observed between LIC and serum ferritin concentration (r2=0.69, p Discussion This study of Asian patients with HbE/thal using R2-MRI, an FDA-approved non-invasive method of evaluation of LIC, reveals a wide range of NTIA and, in parallel, a significant proportion of patients with evidence of liver dysfunction. Our data suggest that the liver is at direct risk from NTIA in HbE/thal at a threshold of 6.35 mg Fe/g dry liver tissue. More robust correlations with dysfunction occurring in other organs may be expected to emerge during longitudinal studies which will be critical to understanding the evolution of organ damage occurring secondary to NTIA in this disorder. These studies are urgently needed to prevent morbidity and premature death in this most common form of beta thalassemia. Disclosures: St Pierre: Resonance Health Ltd: Consultancy, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau. Porter:Novartis: Consultancy, Research Funding; Celgene: Consultancy; Shire: Consultancy.