Correlation Of A Common BIM Deletion Polymorphism And Glucocorticoid Resistance In Immune Thrombocytopenia

Objective Immune thrombocytopenia(ITP)is a common bleeding disorder in childhood,used to be named as idiopathic thrombocytopenic purpura years ago.Anti-platelet antibody induced the increased platelet destruction and decreased platelet production is the main characteristic of ITP.Glucocorticoids(GCs)are the first-line treatment of ITP,but the response rate showed unsatisfactory.In recent years,some special pathogenic genes have been reported may be related to the treatment response of ITP to GCs and the prognosis of ITP patients.Recently,a common intronic 2903bp deletion polymorphism was found only in Asian individuals.The purpose of this study is to investigate the correlation between the common BIM gene intron 2 deletion and the GC-resistance in children with ITP,and the relationship between this BIM deletion and prognosis of ITP children.Methods We conducted a retrospective case-control study from December 2015 to December 2017 in the First Affiliated Hospital of Guangxi Medical University.ITP patients were defined as case group,the clinical data and peripheral blood samples were collected.The healthy children in the outpatient department were randomly selected as normal control group and their relevant information and peripheral blood specimens were obtained after their parents signed the ethical agreement.According to the related ITP clinical bleeding symptom grading standard from an international working group and the evidence-based diagnosis and treatment guideline from the American Society of Hematology,the clinical bleeding symptoms of children with ITP were evaluated,and further the cases were divided into GC-sensitive group and GC-resistance group according to the reaction of ITP children to GCs treatment.The Genomic DNA was extracted from peripheral blood DNA of all included patients and controls,and these DNA were amplified by Polymerase Chain Reaction(PCR)using BIM intron-specific primers to detect the presence of a common 2903bp deletion in the BIM gene intron 2 region.Finally,to insure the accuracy of PCR,we used the direct DNA sequencing to conform the BIM genotyping of each sample.The rate of common BIM gene deletion between GC-resistance and GC-sensitive group in ITP children was compared and analyzed,and the deletion rate of BIM gene between the ITP group and the normal control group was compared either.Results A total of 269 children’s peripheral blood samples were collected,including 124 cases(the range in age from 0.5 to 15 years at the time of initial diagnosis),and 145 cases in the normal control group(limited to children 1 to 14 years of age).Through PCR and electrophoresis,a total of 31 BIM gene deletion samples were detected,including 16 ITP patients(12.9%deletion rate)and 15 healthy children(10.3%deletion),and there was no significant difference in this common BIM gene deletion rate between the two groups(?~2=0.174,P=0.677).According to the reported bleeding score of ITP patients,the bleeding symptoms of ITP patients were scored.The most bleeding score was 1points and 2 points(The proportion were 50.81%and 36.29%respectively),and only one case was classified as 4 points(0.8%)because of intracranial hemorrhage.Through the response of ITP children to GCs treatment,ITP cases were divided into GC-sensitive group and GC-resistance group,of which 53 cases were divided into GC-sensitive group(6 cases were BIM gene deletion type),71 cases were GC-resistance group(BIM gene deletion type in 10 cases).The ratio of BIM gene deletion between the GC-sensitive group and the GC-resistant group was 11.3%and 14.1%respectively.The statistical results showed?~2=0.206,P=0.65 and the difference was no statistically significant.Conclusions Bleeding symptoms in ITP children were mostly mild to moderate,intracranial hemorrhage and other severe parenchymal hemorrhage copious loss of blood with sequelae or life-threatening sequelae have a lower incidence.Although BIM is one of the most important regulator for hematopoietic and autoimmune homeostasis,this common BIM gene intron 2 deletion may not be the predisposing genotype of children’s ITP.The intron 2 deletion of BIM gene was not associated with the GC-resistance in children with ITP.