الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The hemoglobin molecule contained within red blood cells is essential for human life, being the means by which oxygen is transported to the tissues. Each hemoglobin molecule is a tetramer consisting of two pairs of globin chains Hemoglobinopathy refers to a disease state involving the hemoglobin molecule. It results from genetic mutation in one or more genes that affect hemoglobin synthesis. This mutation may alter the structure of the hemoglobin molecule, or result in a reduced rate of hemoglobin synthesis.Sickle cell disease (SCD) results from the substitution of a valine residue for glutamic acid in the beta-subunit of hemoglobin. This leads to its pathological polymerization, with resulting red cell rigidity that causes poor microvascular blood flow, with consequent tissue ischemia and infarction.More recently, an independent spectrum of pathophysiology of blood vessel function has been demonstrated, involving abnormal vascular tone and activated, adhesive endothelium. These vasculopathic abnormalities are attributable to pathways involving hemolysis-associated defects in nitric oxide bioavailability, oxidative stress, ischemia-reperfusion injury, hemostatic activation, leukocytes and platelets. Vasculopathy of sickle cell disease has been implicated in the development of painful vaso-occlusive crisis, pulmonary hypertension, stroke, leg ulceration and priapism. This vasculopathy might also play a role in other chronic organ dysfunction in patients with sickle cell disease.