Beta-thalassemias are genetic disorders in the synthesis of the b-globin chains in hemoglobin. Affected individuals usually begin to exhibit some degree of anemia at about 6 months of age. Therapy for severe anemia involves multiple transfusions. What is the most serious complication of transfusion therapy?

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Iron overload is the most serious complication of transfusion therapy because repeated blood transfusions can lead to excess iron accumulation in the body, which can damage organs such as the heart, liver, and endocrine glands.  Iron is primarily absorbed from the diet, in the duodenum, as either organic or hemebound forms. Inside the enterocyte the iron binds to cytoplasmic proteins, ferritin, and mobilferrin. Depending on total body iron stores, the iron is either transferred to the plasma, where it binds to plasma transferrin, or it remains in the enterocyte until it is lost with cell shedding. Once absorbed, iron is avidly retained by the body. An adult male excretes only about 0.03% of his total body stores per day (about 1 mg), while the loss in premenopausal women is still only about twice that amount. Blood normally contains 15 g of hemoglobin per 100 mL. The concentration of hemoglobin in blood is thus about 2.3 millimolar (mM). Since each molecule of hemoglobin contains 4 molecules of iron, the total blood iron concentration is almost 10 mM. A transfusion of 1 unit of packed red blood cells (about 500 mL) would thus add a total iron burden of about 250 mg. Given the body's limited excretory capacity, multiple transfusions can elevate iron to toxic levels. The liver is particularly susceptible to damage.

Beta-Thalassemias Are Genetic Disorders in the Synthesis of the B-Globin