الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 102 |  |  |
| | | from | 102 | | |
Abstract
Thalassemia syndromes are genetic disorders in globin chain production, characterized by varying degree of ineffective hematopoiesis and increase hemolysis. Their clinical severity varies widely, ranging from asymptomatic forms to severe or even fatal entities. Genetically Thalassemia represents the most common hereditary hemolytic anemia. It has been estimated that about 1.5% of the global population (80 to 90 million people) are carriers of beta-thalassemia gene, with about 60,000 symptomatic individuals born annually, the great majority in the developing world.βTM has been the most common chronic hemolytic anemia in Egypt with a carrier rate ranging from 5.3% to 10.
Life-long blood transfusion is a standard protocol used for the treatment and care of patients with β-thalassemia major. Although lifesaving , chronic blood transfusion however, results in iron overload with subsequent organ and tissue damages.
Oxidative stress is an important mechanism in the progression of β-TM, whose contribution to β-thalassemic anemia is only partially understood. Oxygen free radicals generation process gains importance because of its role in the pathogenesis of a lot of pathological processes and its effect on mortality and morbidity. Oxygen free radicals cause lipid peroxidation, the end product of lipid peroxidation is MDA. The iron chelator DFO has been used for several decades to prevent iron overload in patients with thalassemia, due to its ability to inhibit the redox activity of transition metals through chelation.
Haptoglobin is an acute phase protein that scavenges hemoglobin in the event of intravascular or extravascular hemolysis and reduces the oxidative and peroxidative potential of free Hb. In human populations three common phenotypes are represented: Hp1-1, Hp2-2 and the heterozygous Hp2-1, which is determined by two alleles Hp1 and Hp2 .The unique and peculiar functional activities defined by the phenotypes make consideration of Hp gene polymorphism.
More recently, several functional differences between haptoglobin phenotypes have been demonstrated that appear to have important biological and clinical consequences. Haptoglobin polymorphism is associated with the prevalence and clinical evolution of many inflammatory diseases, including infections, atherosclerosis, and autoimmune disorders. These effects are explained by a phenotype-dependent modulation of oxidative stress and prostaglandin synthesis. The antioxidant role of haptoglobin and the phenotype dependence were confirmed for preventing possible oxidative damage induced by free hemoglobin and iron release during its catabolism.
The aim of the work is to study the impact of haptoglobin gene polymorphism on phenotypic variability in patients with β thalassemia major in relation to iron overload and oxidative stress.
The study was conducted among fifty patients with established βTM, they were on regular RBCs transfusion and all patients were adherent to iron chelation therapy using DFO. Blood samples were collected before blood transfusion, Cases with apparent acute infection were excluded. Twenty five normal apparently healthy individuals of matching age and sex with previous group were served as control. All patients as well control subjects included in the study were subjected to the following:
1. Thorough history taking with special emphasis on patient’s age at first presentation, frequency of blood transfusion and chelation therapy and history of operative procedures(splenectomy). )
2.Complete clinical examination with special emphasis on thalassemic manifestations, hepatomegaly, splenomegaly.
3.Laboratory investigations including:
a)Routine investigation including
-Complete Blood Count (CBC), Blood film, Reticulocytes count, Hb electrophoresis.
-Iron profile (serum iron, total iron binding capacity, transferrin saturation)- Serum ferritin, C- reactive protein (CRP) and Coombs’ test.
b)Special laboratory tests
- Serum haptoglobin (Hp).
- Serum malondialdehyde (MDA).
- Haptoglobin gene polymorphism by PCR.
Data from our study confirm that the decrease of the hemoglobin level in thalassemic group is accompanied by a decrease in the erythrocytes number and by diminished values of their specific indexes (MCV, MCH, PCV,etc.).
The content of mean serum iron (42.30µmol/l) and mean serum ferritin (3287.22 µg/l) were significantly increased above that of the controls in all the patients examined. The study revealed that 32% of thalassemic patients are HCV positive which is higher than the reported prevalence of HCV in Egypt (15-20%). 16% of our patients had a positive antiglobulin test, this is partly attributed to lack of extended phenotyping as a standard routine in our blood banks. In the present study, a significant correlation was found between a positive DAT and a lower serum haptoglobin level (P=0.017) being consumed in the trapping free Hb from circulation.
On the other hand, the lower levels of serum haptoglobin in thalassemic patients could be attributed to the presence of different polymorphisms of the haptoglobin gene. Consequently, the genotype Hp1-1results in the highest level of serum haptoglobin, while Hp2-1 and Hp2-2 are associated with lower serum haptoglobin levels approaching statistical significance (P=0.067).
In the present study, 56% of patients had the Hp2-2 genotype, followed by Hp 2—1 genotype, while in the control, Hp2-1 predominated, the study also revealed that thalassemic patients with Hp2-2 have the highest serum ferritin.
In the present study, a significantly higher level of MDA, a marker of lipid peroxidation was found in patients versus the control,(P <0.001)reflecting a state of significant oxidative stress in patients group. The highest level was found in patients with the Hp2-2 phenotype (P=0.056) as compared with the other phenotypes.
Therefore, we hypothesize that oxidative stress is a major factor of morbidity in β-thalassemic and is correlated with iron overload and metabolic dysfunctions.We have demonstrated that there are functional differences in the antioxidant capacity of the different haptoglobin proteins toward hemoglobin, suggesting that those with haptoglobin 1-1 protein may have superior antioxidant protection than those with Hp 2-2 protein .