الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Thrombocytopenia means decreased platelet count below 150,000∕mm³, thrombocytopenia has many causes but the most common of them in children is ITP.
ITP is an autoimmune disease characterized mainly by isolated thrombocytopenia with normal platelet morphology and other blood cells are normal in count and morphology.
ITP can affect child’s daily activity and performance, it can be acute (lasting less than 3 months) , persistent (3-12 month) or chronic (lasting more than 12 months).
Stromal cell-derived factor-1 (SDF-1) is a chemokine protein belonging to the CXC subfamily of chemokines encoded by the CXCL12 gene on chromosome 10.
SDF1 is secreted by the bone marrow stromal cells and several other cell type it has a transmembrane glycoprotein receptor called ( CXCR4) on megakaryocytic progenitors .It promotes megakaryocytes migration to the vascular niche for maturation, differentiation and platelet release leading to increased number of circulating platelets in peripheral blood so, manipulation of SDF-1 can acutely improve thrombocytopenia. (41)
It has been found that Low level of CXCR4/SDF-1 system in bone marrow may be one of the factors sharing in the development of acute ITP. (42)
Single-nucleotide polymorphisms in the human SDF-1 gene specifically the rs2297630, located on intron 3, +8906 may affect gene transcription and SDF-1 levels , AG genotype is associated with protection from chronic ITP In addition, there was a possible relationship between rs2297630 and corticosteroid dependence in children with ITP.
The aim of the current study was to assess the prevalence of SNP (rs2297630) of SDF1 in 100 ITP children attending Alexandria university children hospital and its relation to chronicity.
The current study was conducted on 100 ITP pediatric patients attending Alexandria University Children Hospital divided in to ; (50 with acute or persistent ITP & 50 with chronic ITP) and 50 normal children serving as control.
By analysis of the results it was found that AG genotype of the SNP (rs2297630) has no significant relation to ITP chronicity or steroid dependence in studied groups.