Both folic acid and cobalamin (vitamin B12) are necessary for the production of DNA; in their absence, the nucleus of the cell cannot undergo normal mitosis. The main cause of folic acid deficiency is dietary insufficiency. (87) This commonly occurs in severe alcoholics. The main cause of cobalamin deficiency is malabsorption. Resection or disease of the terminal ileum removes the site of absorption. The major clinical manifestations of folate or vitamin B 12 deficiency include fatigue, pallor, and for cobalamin deficiency, neuropsychiatric manifestations. The latter include loss of proprioception in the lower extremities, loss of vibratory perception, loss of the sense of smell, forgetfulness, and even dementia. Determining the serum levels of vitamin B12 and folate makes the diagnosis. Treatment is replacement of folate (1 mg/day or improved diet) and vitamin B12 (administered parenterally). After initial treatment, there will be a robust rise in the reticulocyte count 5 to 10 days later.
In cobalamin deficiency, neuropsychiatric findings can occur even when megaloblasts and anaemia are absent. (88) Patients with cobalamin levels between 100 and 200 pg/ml, and especially those with levels less than 100 pg/ml, may have cobalamin-reversible neuropsychiatric deficits. (89> Even dementia due to chronic cobalamine deficiency may be partially reversible when diagnosed and aggressively treated.
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