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A 45-year-old woman presents with complaints of tongue pain, fatigue, paresthesias, anorexia, and early satiety. These complaints have been bothering her over the course of months to years, but she has recently noticed increased tongue swelling and pain. The physical exam and laboratory tests reveal findings consistent with vitamin B12 deficiency, including low hemoglobin, hematocrit, and vitamin B12 levels; elevated MCV and MCH; a low-grade fever; mild tachycardia; mild splenomegaly; and decreased pinprick, vibratory, and temperature sensations in the lower extremities. The peripheral blood smear showed abnormalities commonly seen in vitamin B12 deficiency. Additionally, she is taking both metformin and omeprazole, which are potential causes of vitamin B12 deficiency. Several options for replacement of vitamin B12 are available, and intramuscular (IM), deep subcutaneous (SC), and oral replacement are all potential options for this patient.


Collect Information

1.a. What subjective and objective information indicates the presence of vitamin B12 deficiency?

  • Complaints of fatigue and lethargy1

  • (+) red, smooth, swollen, sore tongue with loss of papillae (atrophic glossitis)2

  • (+) tingling and numbness in feet (paresthesias) and decreased pinprick, vibratory, and temperature sensations in both lower extremities2

  • Decreased hemoglobin, hematocrit, and RBC count

  • Decreased serum vitamin B12 level

  • Elevated MCV and MCH levels1

  • Low-reticulocyte count in the presence of anemia

  • Mild splenomegaly

  • Persistent low-grade fever

  • Mild tachycardia1

  • Anorexia and early satiety

  • Mild thrombocytopenia1–3

  • Peripheral blood smear containing macro-ovalocytosis, hypersegmented granulocytes, large platelets, and macrocytic red blood cells with megaloblastic changes1–3

1.b. What additional information is needed to fully assess this patient’s vitamin B12 deficiency?

  • The main causes of cobalamin deficiency are pernicious anemia, insufficient nutritional vitamin B12 intake, ileal disease and/or resection, and food-cobalamin malabsorption usually caused by atrophic gastritis. This form of gastritis is usually caused by Helicobacter pylori infection or long-term antacid use. Other causes include chronic alcoholism, gastric reconstruction surgery, or chronic pancreatic disease.1–3

  • Information about the patient’s diet would be extremely valuable. Vitamin B12 deficiency is much more common in vegetarians and vegans due to their lack of intake of meat, fish, and dairy products.1

  • Knowing the length of time she has been taking her chronic medications would be valuable to determine whether the metformin and/or omeprazole could be playing a role in her vitamin B12 deficiency.

  • Currently, any vitamin B12 level <150 pmol/L or <200 pg/mL is considered deficient. However, sensitivity and specificity lack with vitamin B12 serum ...

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