Abstract
ABSTRACTObjectives:To evaluate the use of magnetic resonance imaging in patients with β-thalassemia and to compare T2* magnetic resonance imaging results with serum ferritin levels and the redox active fraction of labile plasma iron. We have retrospectively evaluated 115 chronically transfused patients (65 women). We tested serum ferritin with chemiluminescence, fraction of labile plasma iron by cellular fluorescence and used T2* MRI to assess iron content in the heart, liver, and pancreas. Hepatic iron concentration was determined in liver biopsies of 11 patients and the results were compared with liver T2* magnetic resonance imaging. The mean serum ferritin was 2,676.5 +/- 2,051.7 ng/mL. A fraction of labile plasma iron was abnormal (> 0,6 Units/mL) in 48/83 patients (57%). The mean liver T2* value was 3.91 ± 3.95 ms, suggesting liver siderosis in most patients (92.1%). The mean myocardial T2* value was 24.96 ± 14.17 ms and the incidence of cardiac siderosis (T2* < 20 ms) was 36%, of which 19% (22/115) were severe cases (T2* < 10 ms). The mean pancreas T2* value was 11.12 ± 11.20 ms, and 83.5% of patients had pancreatic iron deposition (T2* < 21 ms). There was significant curvilinear and inverse correlation between liver T2* magnetic resonance imaging and hepatic iron concentration (r= -0.878; p < 0.001) and moderate correlation between pancreas and myocardial T2* MRI (r = 0.546; p < 0.0001). A high rate of hepatic, pancreatic and cardiac impairment by iron overload was demonstrated. Ferritin levels could not predict liver, heart or pancreas iron overload as measured by T2* magnetic resonance imaging. There was no correlation between liver, pancreas, liver and myocardial iron overload, neither between ferritin and fraction of labile plasma iron with liver, heart and pancreas T2* values.
Highlights
Beta-thalassemias are caused by mutations of the genes that codify the synthesis of β-globin chains, reducing or eliminating their synthesis
To describe the results found by Magnetic resonance imagining (MRI) T2* in measuring heart, liver and pancreas iron stores, using a measurement technique of T2*, as well as the correlations with serum levels of ferritin and labile plasma iron (LPI) in the Brazilian population of thalassemic patients, which had never been studied by this methodology
Upon analyzing the hepatic iron concentration values found in the liver biopsies and correlating them to MRI T2* values, we found an inverse nonlinear correlation between liver T2* values and iron concentration measured by liver biopsy in the sample of 11 patients who were biopsied (r = -0.878; p < 0.001) (Figure 1A)
Summary
Beta-thalassemias are caused by mutations of the genes that codify the synthesis of β-globin chains, reducing or eliminating their synthesis. Patients with β-thalassemia may develop iron stores beyond the binding capacity of iron carrying proteins, generating an excess of labile plasma iron (LPI) This free iron causes oxidative stress in tissues, resulting in morbidity and mortality[1]. Regular transfusion to maintain the hemoglobin level at about 9 to 10 g/dL started to be used in 1960’s, as standard treatment for patients with thalassemia major and in some cases of thalassemia intermedia This therapy had provided good short-time quality of life, but the deaths by iron transfusion overload affected mainly subjects who were aged 12 to 24 years[5]. The most common cause of death in patients with thalassemia major is heart failure secondary to iron overload This cardiopathy may be prevented or reverted if drugs that reabsorb iron stored in tissues are used. Many studies have shown its high predictive value to detect early iron deposits in these organs, before tissue damage impairs their functioning[7,8,9,10,11]
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