Frequency, Pattern, and Associations of Renal Iron Accumulation in Sickle Beta-Thalassemia
Authors: Pepe Alessia , Barbuto Luigi , Pistoia Laura , Positano Vincenzo , Massei Francesco , Tedesco Letizia , Carrai Valentina , Vitucci Angelantonio , Maggio Aurelio , Peritore Giuseppe , Fina Priscilla , Meloni Antonella 
Published: November 2021

Abstract

Background: Chronically transfused homozygous sickle cell disease (HbSS) patients were shown to have higher kidney iron deposition than thalassemia major patients, not associated to total body iron and mainly caused by chronic hemolysis. Kidney iron deposition has not been explored in sickle beta-thalassemia (Sβ-thal), resulting from the inheritance of both sickle cell and beta-thalssemia genes.
Aim: This multi center study aimed to study frequency, pattern, and associations of renal iron accumulation in sickle beta-thalassemia.
Methods: Thirty-three Sβ-thal patients (36.49±14.72 years; 13 females) consecutively enrolled in the Extension-Myocardial Iron Overload in Thalassemia (E-MIOT) network were considered. Moreover, 20 healthy subjects, 14 HbSS patients and 71 thalassemia major (TM) patients were included as comparison groups. Hepatic, cardiac, pancreatic, and renal iron overload was quantified by the gradient-echo T2* technique. In each kidney T2* was measured in anterior, posterolateral, and posteromedial parenchymal regions and the global T2* value was calculated as the average of the two kidneys T2* values.
Results. Global renal T2* were significantly higher in healthy subjects versus both Sβ-thal patients (49.68±10.09 ms vs 43.19±8.07 ms; P=0.013) and HbSS patients (49.68±10.09 ms vs 26.21±17.07 ms; P&lt;0.0001).
Sβ-thal patients showed comparable age, sex, frequency of regular transfusion, hematochemical parameters, and hepatic, cardiac and pancreatic iron load than HbSS patients, but they had a significant lower frequency of renal iron overload (global renal T2*&lt;31 ms) (9.1% vs 57.1%; P=0.001).
Regularly transfused patients (16 Sβ-thal and 10 HbSS) were compared with TM patients, homogeneous for age and sex, but TM started regular transfusions significantly earlier and they were more frequently chelated. No significant difference was detected in terms of hepatic and cardiac iron levels, but TM patients had significantly lower pancreas T2* values than both the other two groups and significantly higher global renal T2* values than HbSS patients (42.87±9.43 ms vs 24.39±15.74 ms; P=0.001).
In Sβ-thal patients no significant difference was detected between T2* values in left and right kidneys, and global renal T2* values were not associated to age, gender, splenectomy, and they were comparable between regularly transfused and non transfused patients.
No correlation was detected between renal T2* values and serum ferritin levels or iron load in the other organs.
Global renal T2* values were not associated with serum creatinine levels but showed a significant inverse correlation with serum lactate dehydrogenase (Figure 1).
Conclusion. Renal iron deposition is not common in Sβ-thal patients, with a prevalence significantly lower compared to that of HbSS patients, but with a similar underlying mechanism due to the chronic hemolysis.
Figure 1 Figure 1.

Disclosures
Pepe: Bayer S.p.A.: Other: no profit support; Chiesi Farmaceutici S.p.A: Other: no profit support. Maggio: Novartis: Membership on an entity's Board of Directors or advisory committees; Celgene Corp: Membership on an entity's Board of Directors or advisory committees; Bluebird Bio: Membership on an entity's Board of Directors or advisory committees.