questions 4

B12 Deficiency / Pernicious Anemia

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Topic updated on 09/05/17 2:34pm

Snapshot
  • A 72-year-old man of European ancestry presents for a routine check-up with increased fatigue, a smooth shiney tongue and yellowing of his skin.  The man is a strict vegan and refuses to eat anything that casts a shadow.  On physical exam you note markedly decreased vibration sensation and proprioception.  A peripheral smear is ordered demonstrating large RBC's as well neutrophils with nuclei that have 7 lobes.
Introduction

  • A megaloblastic anemia resulting from decreased DNA synthesis with normal RNA/protein synthesis
  • Pernicious anemia is the most common cause of vitamin B12 deficiency
    • antibody to gastric parietal cell leads to ineffective secretion of intrinsic factor (IF) 
    • leads to vitamin B12 deficiency due to decreased uptake in terminal ileum
    • accompanied by achlorhydia and atrophic gastritis
      • atrophic gastritis increases risk of gastric cancer
      • must monitor periodically with fecal occult blood testing
    • found mainly in mature persons of Northern European or African descent
    • neuro findings caused by demyelination
  • Other causes include
    • malabsorption secondary to total or partial gastric resection 
      • loss of IF producing cells
    • resection of terminal ileum
    • drugs
      • azathioprine
      • zidovudine
    • intestinal infections
      • Diphyllobothrium latum
Presentation
  • Symptoms of megaloblastic anemia WITH neurological symptoms
    • neurological findings
      • numbness and parasthesias of the extremities (worse in legs)
      • hyporeflexias
      • decreased vibratory sensation
      • ataxia
      • demetia
    • gastrointestinal findings
      • glossitis
Evaluation
  • Best initial test: CBC and peripheral smear
  • Most accurate test: B12 levels
    • Serum B12 levels can be misleading at times
  • Confirmatory tests
    •  serum methylmalonic acid
    • ↑ homocysteine levels
    • anti-intrinsic factor and parietal antibodies
    • Schilling's test not relevant clinically (but on Step exams)
  • Peripheral blood and marrow smear show
    • hypersegmented neutrophils and megalocytes
      • B12 and folate needed in DNA synthesis
      • defect results in large immature nuclei in all nucleated cells
    • pancytopenia
      • most of these abnormal cells are destroyed
  • Get TSH to rule out hypothyroidism
Differential
  • Macrocytic anemia
    • alcoholism
    • folate deficiency
    • vitamin B12 deficiency
    • hypothyroidism
    • liver dysfunction
    • drugs (methotrexate, phenytoin, trimethoprim, and zidovudine)
Treatment
  • Treat with
    • monthly vitamin B12 injections
      • high dose oral treatment proven to be equivalent in patients that can absorb B12


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Qbank (2 Questions)

TAG
(M2.HE.12) A 27-year-old female presents to the resident health clinic with multiple complaints. She is pleased to report that she came back from a four-month trip to Japan, where she visited some of the best sushi restaurants in the world. However, she has several new complaints. She is fatigued. She also reports that the appearance of her tongue has changed (Image A). Strangely, she has also been losing her balance. Vital signs are stable. Physical examination is significant for decreased position and vibratory sensation in the lower extremities and decreased knee jerks bilaterally. The resident sends a complete blood count which reveals a hemoglobin of 9.0 and a mean corpuscular volume of 110. He initiates folate supplementation. She revisits several weeks later in attending clinic, where you would expect to see the following: Topic Review Topic
FIGURES: A          

1. Her anemia has improved and her neurologic symptoms improved
2. Her anemia has improved and her neurologic symptoms worsened
3. Her anemia has worsened and her neurologic symptoms improved
4. Her anemia and neurologic symptoms have worsened
5. Her cumulative symptoms remain the same

PREFERRED RESPONSE ▶
TAG
(M2.HE.37) A 56-year-old female presents to your clinic 3 years after undergoing a partial gastrectomy for management of a gastrointestinal stromal tumor. The results of her complete blood count and blood smear, which were done prior to her visit today, are significant for: Hemoglobin 9 g/dL, Hematocrit 28%, MCV 112 fL, and a smear showing macrocytes and several hypersegmented neutrophils. Which of the following symptoms or physical exam findings might you expect in this patient? Topic Review Topic

1. Hyperreflexia
2. Night blindness
3. Swollen, shiny tongue
4. Bleeding gums
5. Bruising and petechiae

PREFERRED RESPONSE ▶
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