A 45-year-old man with mild macrocytic anemia has a borderline-normal serum vitamin B 12 level. What is the most appropriate next test to evaluate for vitamin B 12 deficiency? Methylmalonic acid (MMA). MMA levels are elevated in more than 90% of patients with vitamin B 12 deficiency.

 

 

A 43-year-old man who is a chronic alcoholic presents to the hospital with fatigue and a burning sensation in his feet. Laboratory testing is performed, and a peripheral blood smear reveals anemia with hypersegmented neutrophils and oval macrocytes. The patient is given folate, and the anemia resolves. However, the burning sensation in his feet worsens. Which of the following statements best explains this patient's symptomatology?

The patient had megaloblastic anemia due to folate deficiency, and the worsening of the sensation in his feet is unrelated

The patient lacks the ability to absorb the folate due to pancreatic insufficiency from chronic pancreatitis

The patient had a vitamin B12 deficiency, and the treatment with folate partially masked its effects, treating the anemia but not the neurologic changes

The patient's peripheral neuropathy is secondary to thiamine deficiency, and addition of folate to the diet without thiamine supplementation caused increased demand for thiamine and acute worsening of his neuropathy

The correct answer is C.

Both vitamin B12 and folate deficiency will cause a megaloblastic anemia. A vitamin B12 deficiency (not a folate deficiency) is associated with neurologic symptoms. If a patient with a vitamin B12 deficiency is treated with folate supplementation, the treatment will resolve the anemia, but it will not prevent the effects of vitamin B12deficiency on the nervous system. In alcoholics or otherwise malnourished patients with altered mental status, supplementation with both vitamin B12 and thiamine is advisable. Always give thiamine before dextrose in the DONT algorithm (dextrose, oxygen, naloxone, thiamine), because a large glucose load in a thiamine-deficient patient will acutely increase the metabolic need for thiamine and may precipitate Korsakoff syndrome.

 

A person on a strict vegan diet who does not eat meat or animal products (milk, eggs, cheese) and does not take regular multivitamin tablets is most at risk for which vitamin deficiency? Vitamin B 12 . In some patients it may take 10 to 15 years before vitamin B 12 deficiency due to diet becomes clinically apparent.