Iron Overload and Chelation Therapy in Hemoglobinopathies

Abstract

Iron overload (IOL) is highly prevalent among patients with hemoglobinopathies; both transfusion dependent thalassemia (TDT) and non-transfusion dependent thalassemia (NTDT). Whether IOL is secondary to regular transfusions like in TDT, or develops from increased intestinal absorption like in NTDT, it can cause significant morbidity and mortality. In TDT patients, iron accumulation in organ tissues is highly evident, and leads to organ toxicity and dysfunction. IOL in NTDT patients is cumulative with advancing age, and concern with secondary morbidity starts beyond the age of 10 years, as shown by the OPTIMAL CARE study. Several modalities are available for the diagnosis and monitoring of IOL. Serum ferritin (SF) assessment is widely available and heavily relied on in resource-poor countries. Non-invasive iron monitoring using MRI has become the gold standard to diagnose IOL. Three iron chelators are currently available for the treatment of IOL: deferoxamine (DFO) in subcutaneous or intravenous injection, oral deferiprone (DFP) in tablet or solution form, and oral deferasirox (DFX) in dispersible tablet (DT) and film-coated tablet (FCT). Today, the goal of ICT is to maintain safe levels of body iron at all times. Appropriate tailoring ICT with chelator choices and dose adjustment must be implemented in a timely manner. Clinical decision to initiate, adjust and stop ICT is based on SF, MRI-LIC and cardiac T2*. In this article, we review the mechanism of IOL in both TDT and NTDT, the pathophysiology behind it, its complications, and the different ways to assess and quantify it. We will also discuss the different ICT modalities available, and the emergence of novel therapies.