[Association between vitamin D receptor gene Tru9I polymorphism and myasthenia gravis]

To explore the associations between vitamin D receptor (VDR) gene Tru9I polymorphism and myasthenia gravis (MG).

A total of 302 MG patients, diagnosed and treated at Affiliated Hospital of Medical College, Qingdao University and Beijing Friendship Hospital from December 2006 to July 2010, were recruited. And 283 normal subjects were selected as the controls. Tru9I polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The frequencies of genotypes and alleles were compared among different MG subgroups and control group. The relationship between the genotype and susceptibility or severity of MG and immediate efficacies of glucocorticoid were explored. The SPSS17.0 was applied to statistical analysis.

In the MG patients whose age of onset was above 15 years, the frequency of TT and tt genotypes in females was lower than that of the control group. However the frequency of Tt genotype was higher than that of the control group. And there were significant differences (χ(2) = 8.847, P = 0.012). The frequency of Tt + tt genotype in females (58/139, 41.7%) was higher than that of the control group (56/189, 29.6%). And there were also significant differences (OR = 1.70, 95% CI 1.07 - 3.41, χ(2) = 5.169, P = 0.023). Although the frequency of t alleles in females (61/278, 21.9%) was higher than that of the control group (65/378, 17.2%), no significant differences existed (P > 0.05). There were no differences in frequencies of genotypes and alleles between the patients with varying severity and different immediate efficacies of glucocorticoid (P > 0.05).

VDR gene Tru9I polymorphism may be related to the risk of MG in females aged above 15 years.