Hi Thanh,
The yellow pigment is caused by bilirubin which is the product of hemolysis, the breakdown of red blood cells, which happens in thalassemia. While little medical advice is given to reduce this, I do believe that some impact can be made on this by supplementation with specific vitamins and minerals which aid the red blood cells in surviving longer. Please see the recent thread at
http://www.thalassemiapatientsandfriends.com/index.php?topic=1910.msg16077#msg16077 for list of supplements that may have some effect on prolonging red cell life. Recent studies have shown that magnesium is a key mineral in helping to prevent gallstones. Gallstones are formed by the excess bilirubin, and magnesium is known to strengthen the cellular walls, so it is not a strecth to believe that magnesium may have some effect in lowering bilirubin levels. Ideally, you should also be getting transfused before your Hb drops so low. An Hb of 10 or higher will greatly reduce the excess bone marrow activity which is creating more bad red cells for your spleen to remove. This is only adding to the bilirubin levels and the yellow appearance.
You are at the point where you need to make the decision to aggressively chelate before the high iron levels reach your heart. Your liver shows too much iron and at your age, this can be reversed by complete compliance with your chelation at its maximum dosage. Some patients in the US are also taking desferal 2-3 times per week with Exjade. If you don't make progress using Exjade over the next six months, please talk to your doctor about combination chelation with desferal and Exjade.