INTRODUCTION
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B
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-Thalassemia
major is a hereditary hemolytic disorder characterized by a defect in the
synthesis of adult hemaoglobin beta chains, resulting in ineffective
erythropoiesis. Conventional management of B-thalassemia major requires regular
blood transfusion. This leads to excess iron accumulation, initially in the
reticuloendothelial system and subsequently in all parenchymal organs, mainly
heart, pituitary gland, pancreas and gonads, resulting in serious and sometimes
fatal clinical complications (Afroditi and Vassilios, 2006).
Frequent transfusion and subcutaneous des-ferrioxamine
chelation therapy improve the long-term prognosis. But problems related to
secondary hemosiderosis are common. These include endocrine complications,
liver disease and cardiac failure (Roth, 1997).
The most prominent endocrine complication are growth
retardation and the failure of normal pubertal development. Other disorders
such as hypothyroidism, hypoparathyroidism, impaired glucose tolerance and
diabetes mellitus are less frequent (Roth, 1997).
In
the pituitary gland iron toxicity mainly affects the gonadotropine-secreting
cells, therefore, in thalassemic patients; hypogonadotropic hypogonadism is a
frequent abnormality (Roth, 1997). The degree of pituitary iron
overload has been evaluated by MRI (Agyropoulou et al., 2001). A
heavier pituitary siderosis was found in thalassemic patients with
hypogonadotropic hypogonadism than was found in those without pituitary
dysfunction. Hpophyseal damage, secondary to iron overload, might be evaluated
by measuring on MR the pituitary gland height, because the later has been
proven to be a useful marker in the study of pituitary gland dysfunction (Agyropoulou
et al., 2001).
Magnetic Resonance Imaging (MRI) as long been considered
a potential method for assessing tissue iron overload as iron accumulation in
various organs a significant reduction in signal intensity stemming from a
decrease in t2 relaxation time 3. Indeed, in some organs such as myocardium and
pituitary, MRI offers a noninvasive and easily accessible method for assessing
both the presence and the changes in the level of iron accumulation in vivo.
Various MRI techniques for evaluating iron deposition in different organs have
been developed in different centers worldwide (Afroditi, 2006).
Dr.Nada Fathy
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