The association between BsmI polymorphism and bone mineral density in young patients with epilepsy who are taking phenytoin

Purpose: This study sought to determine the association between BsmI polymorphism and bone mineral density, 25-hydroxyvitamin D, and parathyroid hormone levels in patients with epilepsy. Methods: We recruited ambulatory young adults with epilepsy who were taking phenytoin. Data regarding demographics, basic laboratory studies, history of clinical epilepsy, parathyroid hormone, and vitamin D levels, as well as BsmI polymorphism of the vitamin D receptor (VDR) gene, were obtained. The bone mineral density (BMD) of the lumbar spine and left femur were measured using dual-energy x-ray absorptiometry. Key Findings: Ninety-four patients were included in the study. BsmI polymorphism had a statistically significant lower T-score of the lumbar spine and left femoral neck than patients with wild-type VDR gene (p<0.01 and p<0.01, respectively). In addition, patients with BsmI polymorphism had a statistically significant lower z-score of the lumbar spine and left femoral neck than patients with wild-type VDR gene (p<0.01 and p<0.01, respectively). The 25-hydroxyvitamin D level in patients with wild-type genes was higher than in epileptic patients with BsmI polymorphism (p<0.01 and p<0.01, respectively). Parathyroid hormone level in patients with wild-type VDR gene or patients having BsmI polymorphism was not correlated with BMD at either site. Significance: In patients with epilepsy taking phenytoin, having BsmI polymorphism was associated with lower BMD.