OBJECTIVE: Epigenetic changes in gene expression, including DNA methylation and 
histone modifications, might contribute to autoimmunity. DNA methylation is 
mediated by a family of DNA methyltransferases. Polymorphisms of the DNA 
methyltransferase 3B (DNMT3B) gene may influence DNMT3B activity on DNA 
methylation, thereby modulating the susceptibility to some diseases. The purpose 
of this study was to investigate the association between the single nucleotide 
polymorphism (SNP) in promoter of the DNMT3B gene and the risk for development 
of idiopathic thrombocytopenic purpura (ITP).
METHODS: In this hospital-based case-control study, the DNMT3B SNP was genotyped 
in 201 patients with ITP and 136 healthy controls by polymerase chain 
reaction-restriction fragment length polymorphism.
RESULTS: The C/C genotype was not detected in both the patients with ITP and the 
controls. In the controls, the frequencies of T/T and C/T genotypes and T and C 
alleles were 97.8%, 2.2%, 98.9%, and 1.1%, respectively. There was no 
significant difference in genotype and allele distribution between the patients 
with ITP and the controls (P = 0.745 and 0.747, respectively). No significant 
difference was observed in genotype and allele distribution between the two 
groups when stratified by the age. The similar results were shown among the four 
groups of patients with ITP: acute childhood, chronic childhood, acute adult, 
and chronic adult.
CONCLUSION: This polymorphism was distributed similarly between the patients 
with ITP and the controls. It demonstrated that it may not be used as a 
stratification marker to predict the susceptibility to ITP, at least in the 
population of North China.