الفهرس 
Sickle Cell Disease (SCD)Only 14 pages are availabe for public view
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Abstract
Sickle cell disease (SCD) is a genetic disorder caused
by the substitution of the amino acid Valine in place of
glutamate at position 6 of the hemoglobin chain, which
results in significant hemoglobin instability, solubility and
morphological changes -in the form of misshapen red blood
cells that are incapable of normal oxygen exchange-. SCD
is prevalent among people of black African descent and
regions where malaria is endemic (e.g., Africa, the Middle
East, the eastern Mediterranean region and India). The
heterozygous form is associated with increased malaria
resistance (heterozygous advantage).
The clinical hallmark of SCA is the painful acute
‗‗crisis‘‘ that continues to be a treatment challenge despite
therapeutic advances. SCD crises occur with variable
frequency and duration and they often require
hospitalization. SCD crises are characterized by HbS
polymerization, episodic vascular occlusion induced by
sickled RBCs. Pain is thought to follow bone marrow
vasculature infarction, leading to the release of
inflammatory mediators that stimulates afferent nerve
fibers. Vaso-occlusion also follows adherence of circulating blood cells (such as leukocytes) to endothelial
cells, hypercoagulability, endothelial dysfunction, altered
nitric oxide (NO) metabolism and ischemia-reperfusion
injury.
Vitamin D is a fat-soluble vitamin naturally present in
few foods, added to others and available commercially as a
dietary supplement. Because most humans can achieve
adequate levels of vitamin D through sun exposure, vitamin
D is often considered to be a prohormone rather than a true
vitamin. Although there is insufficient evidence to prove
that vitamin D supplementation will prevent bone fractures
in healthy individuals with adequate vitamin D levels, in
vitamin D insufficient populations, vitamin D is important
for bone mineralization and deficiency can result in bone
fractures and musculoskeletal pain. Many studies showed
that marked vitamin D deficiency is prevalent among SCD
patients. Rovner et al. found that African American
children with SCD had higher rates of vitamin D deficiency
when compared to non-SCD African-American children
living in the same neighborhoods and suggested that poor
diets that are related to low socioeconomic status were not
associated with vitamin D deficiency. Several mechanisms
were suggested as the likely cause of the low serum vitamin D levels among SCD patients, such as low cutaneous
synthesis, decreased intestinal absorption, disturbance of
adipose tissue metabolism and chronic hemolysis.
In our study, a significant correlation was found
between vitamin D deficiency, frequency and severity of
VOC episodes. A significant correlation was also found
between patients‘ quality of life and vitamin D deficiency.
Regression analysis had shown that there is an independent
correlation between vitamin D level and VOC severity and
frequency.
Vitamin D deficiency is a major health problem in
patients with SCD that may exacerbate the disease,
increases the severity of crisis episodes and the risk of
complications. More prospective and interventional studies
are mandatory to confirm the association between VDD
and SCD complications and the effect and appropriate
dosing of vitamin D before recommending vitamin D as an
adjunct therapy in SCD management. Occasional
monitoring of vitamin D levels and treating deficiencies are
encouraged as primary care points in patients with SCD.