Glomerular hyperfiltration and proteinuria in transfusion-independent patients with β-thalassemia intermedia

Renal manifestations have been described in β-thalassemia major and were attributed to transfusional iron overload and chelation therapy. Patients with the milder phenotype, β-thalassemia intermedia (TI), remain largely transfusion and iron chelation independent while enduring a chronic hemolytic anemia and primary iron overload. Data on renal function in patients with TI is lacking.

In this cross-sectional study of 50 TI patients, we evaluated the association of estimated glomerular filtration rate (eGFR) and urinary protein to creatinine (UPr/UCr) ratio with relevant patient, disease and laboratory indices.

The median age of patients was 28 years (44% males). The eGFR was >90 ml/min/1.73 m(2) in all patients, with a median value of 142.3 ml/min/1.73 m(2). The median UPr/UCr ratio was 213.2 mg/g. There was a negative correlation between age and eGFR, while the UPr/UCr ratio correlated positively with markers of anemia, hemolysis and iron overload. A total of 24 (48%) patients had evidence of glomerular hyperfiltration, while 7 (14%) had proteinuria (UPr/UCr ratio >500 mg/g). Patients with proteinuria were characterized by elevated liver iron concentration (>7 mg Fe/g dry weight), non-transferrin-bound iron levels and nucleated red blood cell counts.

A considerable proportion of TI patients show evidence of abnormally elevated eGFR, with a declining trend towards advancing age. The occurrence of proteinuria is associated with anemia, hemolysis and iron toxicity.