Interferon Gamma +874A/T Polymorphism in Children with Idiopathic Thrombocytopenic Purpura

A recent study showed that expression of Toll-like receptor and interferon-gamma associated genes is significantly increased in patients with chronic ITP. Interferon-gamma is an important protein which takes place in immunoregulation. +874A/T polymorphism in the first introne of interferon gamma gene is found to be associated with the development and clinical phenotype of some autoimmune diseases such as diabetes mellitus, thyroiditis, multiple sclerosis, and SLE. The aim of our study was to investigate whether interferon gamma +874A/T polymorphism is a risk factor for the development of ITP and whether it affects the clinical course and response to the treatment. Thirty five children with acute ITP and 40 children with chronic ITP who were followed for at least 6 months were included. Control group consisted 90 healthy children. Two millilitres of blood sample was taken into sterile tubes containing 0.1% EDTA from each child and all blood samples were stored at −20 until analysis. DNA was isolated from blood samples and interferon gamma +874A/T polymorphism was studied with real-time PCR and LightCycler TM. Twenty one patients had AA, 35 patients had AT, and 19 patients had TT genotype. In the control group, 47 children had AA, 36 children had AT, and 7 children had TT genotype. There was a statistical difference between ITP and control group regarding the genotype (p=0.001). The frequency of A and T alleles in ITP group was 52% and 48%, respectively. The frequency of A and T alleles in control group was 72.7% and 27.8%, respectively. The frequency of allele distribution was statistically different between the ITP and control groups (p<0.0001). There was a statistical significant difference between acute ITP and control group regarding the frequency of AA, AT, and TT gene polymorphisms and allele frequency (p=0.002, p=0.002). Similarly, there was a statistical significant difference between chronic ITP and control group regarding the frequency of AA, AT, and TT gene polymorphisms and allele frequency (p=0.008, p=0.002). The frequency of AA, AT, and TT gene polymorphisms and allele frequency showed no statistical difference between acute and chronic ITP groups (p=0.285, p=0.896). There was no correlation between interferon gamma +874A/T polymorphism and severity of bleeding (mild, moderate and severe) (p=0.09). There was no correlation between interferon gamma +874A/T polymorphism and response to long term treatment in patients with chronic ITP (p=0.568). In conclusion, there was a significant difference between patients with ITP and children in control group regarding interferon gamma +874A/T polymorphism and in the light of recent data involving other autoimmune disorders, we think that interferon gamma +874A/T polymorphism may be a risk factor for ITP.