A 53-year-old female treated with high-dose folic acid for anemia experiences a moderate increase in her hemoglobin level. She returns to clinic complaining of bilateral foot numbness and difficulty in walking. The latter symptoms are most likely related to which of the following?

Question

A 53-year-old female treated with high-dose folic acid for anemia experiences a moderate increase in her hemoglobin level.  She returns to clinic complaining of bilateral foot numbness and difficulty in walking.  The latter symptoms are most likely related to which of the following?

Quizplus · Accepted Answer

The clinical decision to treat this patient with folic acid suggests that her anemia was megaloblastic and therefore likely secondary to a deficiency in folate and/or vitamin B₁₂ (cobalamin). Her subsequent development of neurological symptoms (a finding not associated with folate deficiency alone) indicates that she is deficient in vitamin B₁₂. A moderate improvement in the hemoglobin level often occurs when a deficiency in vitamin B₁₂ is treated with folate, or vice versa. However, the treatment of vitamin B₁₂ deficiency with folate will not reverse any neurologic dysfunction caused by the vitamin B₁₂ deficiency. In fact, the usage of folate alone can worsen demyelination and cause abnormal myelin synthesis by depleting the concentration of unmethylated cobalamin available for methylmalonyl-CoA processing. The walking difficulties and paresthesias seen in this patient were therefore likely precipitated by the administration of folate alone. (Choice A) High doses of folate may antagonize phenytoin, thereby precipitating seizures in a select group of patients. Walking difficulties and paresthesias are not typically associated with folate overdose, however. (Choice B) Iron deficiency is characterized by a hypochromic, microcytic anemia that is best treated with iron supplementation. Walking difficulties and paresthesias are not typically associated with iron deficiency anemia. (Choices D and E) Anemia of any cause can provoke nonspecific neurologic symptoms (eg, tinnitus, irritability, generalized weakness). Walking difficulties and paresthesias are not commonly associated with hemolysis or aplastic anemia, however. Educational Objective: Deficiency of vitamin B₁₂ is associated with both megaloblastic anemia and neurologic dysfunction, while folate deficiency is associated with megaloblastic anemia alone. Moderate improvement in the hemoglobin level often occurs when a deficiency in vitamin B₁₂ is treated with folate, or vice versa. Treatment of vitamin B₁₂ deficiency with folate alone can actually worsen neurologic dysfunction.

A 53-Year-Old Female Treated with High-Dose Folic Acid for Anemia