Liver and Cardiac Iron Measurements in Very Young Chronically Transfused Patients Show Dangerous Levels of Iron Loading

Abstract 1086

Recurrent blood transfusion results in significant iron overload that can cause serious organ damage and death if not properly treated. Liver iron concentration (LIC) is the best indicator of total body iron status and can be measured non-invasively by magnetic resonance imaging (MRI). In the past, it was recommended that LIC assessments by liver biopsy begin after about 6 years of age (yo). MRI is also an excellent way to monitor iron cardiomyopathy, which remains a major cause of death in chronically transfused patients. To understand how rapidly iron overload develops, we reviewed the 1316 MRI iron studies we have performed since 2002 and summarized the LIC and cardiac R2* in a subset of 127 subjects who had their first MRI studies before 10 yo.

Because of the known serious pitfalls in the assessment of total body iron by measurement of ferritin, LIC is measured by MRI in our center as standard of care in all patients on chronic transfusion soon after the start of iron chelation therapy. Most children less than 6 years of age require general anesthesia for this procedure. In some older children cooperation can be achieved by distraction techniques. Thirty three percent had sickle cell disease (SCD), 33% thalassemia major (TM), 11% Blackfan Diamond anemia (DBA), 3% congenital dyserythropoietic anemia (CDA), and 8.6% had other transfusion dependent anemias (OTRAN) and 11.4% had studies done not related to transfusion. This paper will focus on the 114 subjects whose MRI was done to evaluate transfusion related iron overload. The median age at first MRI was 6 years with 25% having their first study before 3.7and 10% before 2.1 yo. The median LIC was 9.8 mg/g dry weight (dw) and 10% of subjects had a first LIC > 22 mg/g dw. Only 2.5% had evidence of cardiac iron (T2* < 20ms). The median LICs (mg/g dw) were 8.9 for SCD, 11.8 for TM, 13 for DBA, 6.1 for CDA, and 8.7 OTRAN and were not statistically different. The minima ranged from 0.6 in OTRAN to 4.2 for CDA and the maxima ranged from 25 in CDA to 39.7 for SCD. There was significant iron loading even when we restricted the analysis to 27 subjects with a first MRI at < 3.5 yo; SCD (2.3 median (med), 2.8 maximum (max)), TM (14.6 med, 35 max), DBA (13 med, 15 max),CDA (6.6 med, 25 max) and OTRAN (5.8 med, 11 max). There were 4 subjects who had evidence of cardiac iron loading. Two had DBA with T2* of 18 ms and 16 ms at 2.5 and 3.7 years of age respectively. A third DBA subject had a T2* of 20 ms at only 4.6 yo. Two TM subjects had a T2* of 15 ms at 6.6 and 9.1 yo respectively.

These data indicate that there is significant elevation in LIC by the age of 3.5 years with a median LIC of 11 mg/g dw and 25% of subjects having a LIC > 15 mg/g dw. These are very high levels of iron loading. Furthermore, 2.5% of subjects in this age already have evidence of cardiac iron loading.

On the basis of such findings, direct measurement of liver iron by MRI is essential as soon as possible after the start of regular transfusions and cardiac iron should be measured early in high risk children with Diamond Blackfan anemia and thalassemia major.