Beta thalassemias are a group of common monogenic disorders, with the highest prevalence in the Mediterranean region, Africa, and Southeast Asia. However, beta thalassemias are increasingly being diagnosed in other parts of the world, largely because of migration from the countries where they have traditionally been observed. An estimated 20.7% of the world population carries a beta thalassemia variant, and approximately 40,000 children are born each year with beta thalassemia.
Typically presenting early in life with profound anemia, patients with beta thalassemia usually require regular blood transfusions, which in turn are associated with iron overload leading to multiple organ dysfunction. Iron chelation therapy, as well as advances in the knowledge of the disease, has helped to improve survival, but many patients continue to experience complications including cardiopulmonary disorders, endocrine organ diseases, liver impairment, and thromboses. Beta thalassemia can also affect the kidney, though its effect on the renal system has not been extensively evaluated.
In a paper published in Hematology, researchers discussed the most common pathophysiologic and clinical manifestations of renal disease in patients with beta thalassemia.
“In recent years, the life expectancy of patients with thalassemia has increased, and this has allowed previously unrecognized renal complications to reveal themselves,” said lead author Christos Demosthenous, MD, of the George Papanicolaou General Hospital of Thessaloniki in Greece. “Although renal disease is a rare cause of morbidity, approximately 60% of patients with thalassemia are expected to experience renal complications.
“Therefore,” he continued, “there is a need to increase awareness among physicians about [the benefits of] closer monitoring and follow up of renal function in patients with thalassemia. Early diagnosis and appropriate intervention will prevent subsequent adverse events from emerging.”
Dr Demosthenous and colleagues conducted a comprehensive literature review in order to summarize the published evidence on the epidemiology and pathophysiology of renal disease in patients with thalassemia. Their data included information from sources published in English since 1990.
As renal complications in this setting have not been extensively studied, information on their epidemiology is limited. Cross-sectional studies looking at different thalassemia groups, drawn from 5 different thalassemia centers in North America, showed reduced creatinine clearance in 7.8% of patients and albuminuria in up to 59% of patients. A more recent study found that 1.8% of patients with transfusion-dependent thalassemia (TDT) had some degree of renal dysfunction. In another paper, renal complications were the fourth most common cause of morbidity (4%) in patients with thalassemia, after endocrine (44.7%), cardiovascular (41.3%), and hepatic (40.5%) disease. At present, however, there are no data from large observational cohorts on the prevalence of chronic kidney disease “following contemporary definitions in patients with beta thalassemia,” the review authors noted.
The primary underlying mechanisms of renal injury appear to be chronic anemia, hypoxia, and iron overload, although some studies suggest that iron chelators may contribute as well.