Osteomalacia can be precipitated in some patients who have been treated with phenytoin and phenobarbital by several factors including inadequate intake of vitamin D, reduced level of physical activity, and insufficient exposure to sunlight. Phenytoin is also known to cause cerebellar atrophy. We report a 41-year old woman who was presented with severe bone pain on the extremities and diffuse cerebellar dysfunctions, hypocalcemia, hypophosphatemia, increased activity of alkaline phosphatase, high level of parathyroid hormone, low level of calcitonin, and low levels of 25-hydroxyvitamin D and 1,25-dihydoxyvitamin D were notel, Osteocalcin level and the amount of urinary pyridinoline excretion were also increased. Bone density of spines and femurs was remarkably decreased, and bone scan showed a diffuse increased uptake. Brain MRI revealed diffuse cerebellar atrophy. Treatment with 1,25-hydroxyvitamin D and calcium improved the symptoms and biochemical parameters. This case provides a lesson that the reduced level of physical activity caused by cerebellar atrophy as well as inadequate supply of vitamin D is likely to aggravate osteomalacia in patients who should be on a long-term treatment with phenytoin.
