Clinical implications of genetic polymorphisms in blepharospasm

The possible genetic variants associated with blepharospasm (BSP) and facial dystonia have been investigated. Although genetic variants associated with BSP have been extensively studied, the contribution of single-nucleotide polymorphisms towards this condition remains poorly understood. In addition, the etiology of BSP remains to be fully elucidated. Therefore, the present study aimed to assess the role of polymorphisms in the torsin 1A (TOR1A), dopamine receptor D (DRD)2 and DRD5 genes in South Korean patients with BSP. Furthermore, the role of genetic variants of these three aforementioned genes was investigated. A prospective case-control study was established, where 56 patients with BSP and 115 healthy controls were recruited at the Department of Ophthalmology of CHA Bundang Medical Center (Seongnam, South Korea) using single nucleotide polymorphisms analysis by real-time PCR. The TOR1A rs1182CC/DRD5 rs6283TC genotype combination was found to be associated with decreased BSP risk [adjusted odds ratio (AOR), 0.288; P=0.013]. DRD5 rs6283 was observed to be associated with the periocular type of BSP in the co-dominant (for the TC genotype; AOR, 0.370; P=0.029) and dominant models (AOR, 0.406; P=0.029). The recessive model of TOR1A rs1801968 (AOR, 0.245; P=0.030), and the recessive (AOR, 0.245; P=0.029) and over-dominant models (AOR, 2.437; P=0.019) of DRD2 rs1800497 were found to be associated with superior responses to botulinum neurotoxin A (BoNT) treatment. By contrast, dominant (AOR, 0.205; P=0.034) and additive (AOR, 0.227; P=0.030) models of DRD5 rs6283 were associated with poor responses to BoNT treatment. To conclude, these results suggested that DRD2 rs1800497 can confer genetic susceptibility to BSP responses to BoNT treatment, whereas the TOR1A rs1182CC/DRD5 rs6283TC genotype combination appeared to contribute to the association with BoNT efficacy in BSP.