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

SummaryPurpose:  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.