A manganese superoxide dismutase gene polymorphism and development of vulvar vestibulitis syndrome following physical vaginal trauma

Objective. Vulvar vestibulitis syndrome (VVS) is a disorder characterized by an inability to experience pain-free vaginal penetration. We hypothesized that one mechanism resulting in VVS was an inability to effectively inactivate reactive oxygen species that were induced by a local physical insult. Methods. VVS patients (190) and controls (194) were tested for a polymorphism at position 1183 in the manganese superoxide dismutase (MnSOD) gene. Carriage of the variant V allele is associated with reduced antioxidant activity. Results. There was no association between a diagnosis of VVS and either the V,V genotype or the allele V frequency. However, when the VVS patients were differentiated with regard to pain tolerance, carriage of the V,V genotype (p =.019) as well as the allele V frequency (p =.026) were both associated with a selfreported inability to tolerate vaginal penetration. Women whose VVS began following childbirth had the highest frequency of intolerance to vaginal penetration (9 of 13, 69.2%) as compared to all other patients (65 of 168, 38.7%) (p =.040). The MnSOD V,V genotype was also more frequent in women whose VVS began following an obvious vaginal trauma (childbirth or gynecological surgery (29.4%) than in women with other, or no identifiable, precipitating cause of their symptoms (10.0%) (p =.033). Conclusion. A decreased capacity to prevent oxidative nerve damage following a localized physical trauma due to carriage of the MnSOD gene polymorphism is associated with the onset of VVS in a subset of women.