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Review Question - QID 107861

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QID 107861 (Type "107861" in App Search)
A 50-year-old female comes into your office with concerns of falling. She states that over the last few months, she has a feeling of numbness and "tingling" in her feet. She denies any problems with her balance and denies vertigo, but does not feel "sure-footed." She denies any neurological history. Past medical history is significant for hysterectomy 10 years ago for menorrhagia and a bowel resection for Crohn's disease. On exam, the patient has decreased reflexes and sensation bilaterally in her lower extremities. CBC shows a Hgb of 9.1 with an MCV of 105. The peripheral blood smear is shown in Figure A. The patient's methylmalonic acid (MMA) level is elevated. What is the most likely cause?
  • A

Vitamin B3 deficiency

0%

0/15

Vitamin C deficiency

0%

0/15

Folate deficiency

7%

1/15

Vitamin B12 deficiency

87%

13/15

Iron deficiency

0%

0/15

  • A

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A patient with a history of small bowel resection presenting with megaloblastic anemia and elevated methylmalonic acid (MMA) level is likely suffering from Vitamin B12 deficiency.

Vitamin B12 deficiency can result from a number of factors such as pernicious anemia, gastritis, gastric bypass surgery, resection of small bowel (particularly terminal ileum), malabsorption (sprue, enteritis), and poor intake (vegan diets). Deficiency typically presents with macrocytic anemia (MCV>100) with the presence of hypersegmented neutrophils (megaloblastic). Unlike folate deficiency, B12 deficiency results in elevated MMA and homocystine levels while folate deficiency results in elevated homocysteine levels only.

Langan et al. discuss vitamin B12 deficiency and present an updated review. They state that patients with B12 deficiency present with neuropsychiatric symptoms such as memory loss, ataxia, parasthesias, and loss of propioception (especially in those older than 50 years). They also state that repletion of vitamin B12 (1 to 2 mg daily) through the oral route is as effective as an intramuscular injection, but warn that the neuropsychiatric symptoms are not always reversible.

Oberlin et al. present the adverse effects of vitamin B12 deficiency. They state that people with B12 deficiency (define in this cohort as serum B12 < 200 pmol/L and serum homocysteine > 20 µmol/L) were more likely to manifest with peripheral neuropathy (odds ratio 9.7, P=0.004) and greater total disability (odds ratio 19.6, P<0.01) even when adjusted for age, sex, race, serum creatinine, and ferritin concentrations, smoking, diabetes, and peripheral artery disease.

Figure A shows a neutrophil with more than 5 lobes, a hypersegmented neutrophil.

Incorrect Answers:
Answer 1: Vitamin B3 (niacin) would typically also have the "3 D's": diarrhea, dermatitis, and dementia.
Answer 2: Vitamin C deficiency would typically present with gum hypertrophy, easy bleeding and bruising, corkscrew hair, and most likely a normocytic anemia.
Answer 3: Folate deficiency would have a similar presentation to the question, but would present with a normal methylmalonic acid level.
Answer 5: Iron deficiency anemia would most commonly present with microcytic anemia.

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