A Case of Osteomalacia with Multiple Fractures and Hypocalcemia Associated with Phenytoin Therapy

Many studies have shown that patients taking antiepileptic drugs are at an increased risk for metabolic bone disease and low bone mineral density. Traditionally, this has been attributed to alterations in vitamin D metabolism by antiepileptic drugs which induce hepatic microsomal cytochrome P450 enzyme. However, there appear to be multiple mechanisms for antiepileptic drug-induced bone loss including lack of physical activity, reduced sunlight exposure, increased propensity for falling, and fractures associated with seizures or loss of consciousness. We experienced a case of antiepileptic drug-induced osteomalacia in a 63-year-old woman who had been on phenytoin for 8 years and was admitted with hypocalcemic seizures and multiple pathological fractures. This patient also had other risk factors for osteomalacia including reduced sunlight exposure, prolonged immobilization, and decreased dietary vitamin D intake. We discontinued phenytoin, and started calcium and vitamin D replacemen t. The patient's serum calcium and vitamin D level were normalized after treatment. Metabolic bone disease including osteomalacia should be considered in patients who are taking antiepileptic drugs especially those who are exposed to other risk factors. (J Korean Endocr Soc 24:212~216, 2009) ꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏ