In the cases of intermediate thalassemia and major thalassemia without transfusions the body tries to compensate for the severe anemia through absorption, in the digestive tract, of a significantly greater amount of iron than usual (2-5g/year as compared to 0.0015g / year in healthy individuals), to produce more red blood cells. Most part of iron absorbed depends on severity of the anemia: the more severe, more will the bone marrow expand to try to produce more and more red blood cells and, therefore, the greater the demand for iron. Other factors may also influence in the amount of iron absorbed in the intestinal tract. For example, the presence of vitamin C increases the amount of iron absorbed, while the tea and some cereals reduce it. However, the most important form of reducing the amount of iron absorbed in the intestinal tract is assuring that patients keep appropriate levels of hemoglobin. Therefore, it is important that they receive regular blood transfusions, keeping the hemoglobin levels above 9g / dl (measured previously to transfusion). Patients not appropriately transfused may absorb from 1 to 5 mg extra per day (or approximately 0.4 to 2g / year) of iron in the intestinal tract.
The major origin of iron overload in patients receiving transfusions, however, is the transfused blood. In fact, the amount of iron the patient absorbs through blood transfusions is quite greater than the amount absorbed from the diet in the intestinal tract. Therefore, it is important that patients receiving regular blood transfusions use iron chelating agents – drugs that are connected to the iron and that remove it from the system amount.
Each milliliter (ml) of red blood cells contains around 1.16mg of iron. An average blood unit contains around 250 ml of red blood cell concentrate – that is – 250 x 1.16, or around 200-290mg of iron. The degradation of these red blood cells is the main source of iron accumulated in the organism of patients receiving blood transfusions throughout life. For example, a patient receiving 30 blood units per year will have an excess of approximately 6 g of iron per year (200x30 = 6.0mg = 6g), or approximately 15-16mg/day. The body is not capable of excreting so large amount of extra iron and this iron is accumulated in the tissues and organs of the body. If this iron is not removed through medical intervention it may be extremely damaging and cause some of the most severe complications of the major thalassemia.
The clinical symptoms of the iron overload usually appear around the 10 years of age, although evidences of the toxic effects of iron have been found in the liver of children much younger. The injury to the liver – known as fibrosis – is initiated within two years after beginning of the transfusions. A severe injury in the liver (cirrhosis) may develop before the 10 years of age if no treatment is implemented to remove the excess iron, mainly if the patient has hepatitis B and/ or C. Cardiac diseases – one of the most frequent death causes in the major thalassemia – are also reported within a period of 10 years after beginning of the transfusion program, although cardiac insufficiency usually does not occur before the 15 years or more of transfusions.
The iron overload is also the most important cause of the sexual maturation retardation in patients with thalassemia, affecting approximately half of the patients, both from the female and male genders. Furthermore, the iron overload may bring difficulty for women who want to have a child (around 25% of the cases), and is, usually, a cause for development of diabetes mellitus.
In the long term, the excess iron causes bone complications and damages to other important organs, such as the thyroid and the parathyroid. Therefore, the patients should be treated for its removal; otherwise, the iron will be accumulated in the organism, with serious consequences in terms of quality and extension of the patient's life.