Acquired proximal renal tubular dysfunction in β-thalassemia patients treated with deferasirox.

Deferasirox is a recently approved oral iron chelator for treatment of patients with transfusion-related iron overload. Although renal function disturbances were recognized, proximal renal tubulopathy was not addressed in published safety reports for deferasirox. Although subclinical proximal tubulopathy was described in β-thalassemia homozygotes, overt Fanconi kidney is not an established disease complication. We describe 4 cases out of 50 children and adults with transfusion-dependent β-thalassemia, treated with deferasirox for iron overload, who developed clinically significant Fanconi syndrome. Three had concomitant infectious events; the fourth case was entirely spontaneous. In addition, all 4 patients were moderately to well chelated. Cessation of deferasirox resulted in prompt recovery. We propose the necessity for diligent monitoring for proximal tubule nephropathy, possibly related to infectious events, during treatment with deferasirox.