Endothelial nitric oxide synthase (eNOS) Glu298Asp gene polymorphism in the cases of idiopathic thrombocytopenic purpura

Endothelial nitric oxide synthase (eNOS) Glu298Asp gene polymorphism in the cases of idiopathic thrombocytopenic purpuraIdiopathic thrombocytopenic purpura (ITP), which is an acquired autoimmune and selflimiting disease has a benign course and characterized by thrombocytopenia. Pathogenesis of the disease include auto-antibodies formed against platelets or other auto-immune mechanisms resulting in cellular damage with formation of hydrogen peroxide which is an oxidant yield.Oxidative stres and free-radicals could be responsible in the pathogenesis and prognosis of ITP which is an autoimmune disorder. High doses of nitric oxide results in the formation of toxic molecule peroxynitrite in the presence of cellular superoxide anion. Peroxynitrite may cause cellular injury with lipid peroxidation, DNA fragmentation and depletion of plasma antioxidants. Polymorphism of endothelial nitric oxide synthase (eNOS) gene which supplies nitric oxide synthesis changes the functions of this enzyme.This study investigated the role of eNOS Glu298Asp gene polymorphism in ethiopathogenesis, course and treatment of ITP. 66 patients including 51 acute and 15 chronic ITP and 60 healthy controls were enrolled in the study. In all patients with ITP and in the groups with acute, chronic ITP and healthy group, the frequency of GG genotype were found as %40.9, %39.2, %46.7 and %21.7, respectively, meanwile the frequency of GT genotype were %48.5, %51, %40, %70 and TT genotype were %10.6, %9.8, %13.3 and %8.3, respectively. Most common genotype in all patients with İTP, acute İTP group and control group was GT genotype, while GG genotype was found predominantly in patients with chronic ITP.In the present study, a significant correlation was found between ITP and eNOS Glu298Asp gene polymorphism. This correlation gave rise to thought that eNOS Glu298Asp gene polymorphism might be a risk factor in the ethiopathogenesis of ITP. Patients with GG genotype was thought to have a high intention for having a chronic disease due to high frequency of GG genotype in patients with chronic ITP. Patients with acute, chronic ITP and having GG genotype, responded effectively to medical treatment with IVIG therapy mainly (except anti-D). However, patients having GT and TT genotypes in the chronic ITP group were resistant to medical therapy. Presence of G allel was observed to have a positive and T allel to have a negative affect in the medical treatment of patients with chronic ITP.Key words: Idiopathic thrombocytopenic purpura, endothelial nitric oxide synthase Glu298Asp gene polymorphisim, intravenous immunoglobuline.