Case report: subacute combined degeneration of the spinal cord from folate deficiency.

Subacute combined degeneration of the spinal cord is a rare neurologic complication of folate deficiency. Progressive gait disturbance, weakness, confusion, and depression developed in a 39-year-old man. He had taken phenobarbital for more than 2 years. He was bedbound, with new loss of position and vibration senses in the lower extremities. His hemoglobin was 2.9/dl, mean corpuscular volume 122 fl, vitamin B12 428 pg/ml, and folate 1 ng/ml. Peripheral blood and bone marrow showed megaloblastic anemia. Serum methylmalonic acid and homocysteine levels were consistent with folate deficiency, not B12 deficiency. Treatment with folate and packed erythrocytes resulted at 4 months in overall improvement, including walking. Position sense was restored, and vibration sense had become nearly normal. The authors found no cause for folate deficiency except phenobarbital.