Background: Tryptophan hydroxylase-2 (TPH2) is a potential candidate gene for screening tic disorder (TD).\r\nMethods: A caseââ?¬â??control study was performed to examine the association between the TPH2 gene and TD. The\r\nSequenomW Mass ARRAY iPLEX GOLD System was used to genotype two single nucleotide polymorphisms (SNPs) of\r\nthe TPH2 gene in 149 TD children and in 125 normal controls.\r\nResults: For rs4565946, individuals with the TT genotype showed a significantly higher risk of TD than those with TC plus\r\nCC genotypes [odds ratio (OR) =3.077, 95% confidence interval (CI): 1.273ââ?¬â??7.437; P = 0.009], as did male TD children with\r\nthe TT genotype (OR = 3.228, 95% CI: 1.153ââ?¬â??9.040; P = 0.020). The G allele of rs4570625 was significantly more frequent in\r\nTD children with higher levels of tic symptoms (Yale Global Tic Severity Scale, YGTSS) than those in controls among the\r\nmale children (OR = 1.684, 95%: 1.097ââ?¬â??2.583; P = 0.017]. TD children with severe tic symptoms had significantly higher\r\nfrequencies of rs4546946 TT genotype than did normal controls in boys (OR = 3.292, 95% CI: 1.139ââ?¬â??9.513; P = 0.022). We\r\nalso found that genotype distributions of both SNPs were different between the Asian and European populations.\r\nConclusions: Our results indicated that the TT genotype of rs4565946 is a potential genetic risk factor for TD, and the\r\nallele G of rs4570625 might be associated with the severity of tic symptoms in boys. These polymorphisms might be\r\nsusceptibility loci for TD in the Chinese Han population. Because of the confounding of co-existing attention deficit\r\nhyperactivity disorder (ADHD),these findings need to be confirmed by studies in much larger samples.
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