Vitamin B12 Deficiency Causes and Manifestations
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Questions and Answers

What is the primary cause of vitamin B12 deficiency among vegetarians?

  • Autoimmune destruction of the gastric parietal cells
  • Gastrectomy
  • Insufficient sunlight exposure
  • Malabsorption
  • Dietary causes (correct)
  • What is the main manifestation of vitamin B12 deficiency known as pernicious anemia?

  • Methylmalonic aciduria
  • Neurological manifestations
  • Megaloblastic anemia (correct)
  • Iron-deficiency anemia
  • Hyperhomocysteinemia
  • What does B12 deficiency lead to, resulting in symptoms of megaloblastic anemia?

  • Decreased accumulation of methyl-THF
  • Impaired utilization of methyl-THF (correct)
  • Increased absorption of vitamin B12
  • Enhanced conversion of methyl-THF to other forms of THF
  • Excessive production of THF forms
  • What is the possible cause of hyperhomocysteinemia and homocystinuria in vitamin B12 deficiency?

    <p>Failure to metabolize homocysteine</p> Signup and view all the answers

    What is the effect of B12 deficiency on the utilization of methyl-THF for the conversion of homocysteine to methionine?

    <p>It impairs the conversion process</p> Signup and view all the answers

    Which form of cells is most affected by the deficiency of THF forms due to B12 deficiency?

    <p>Rapidly dividing cells such as erythropoietic cells</p> Signup and view all the answers

    What is the primary cause of vitamin B12 deficiency known as pernicious anemia?

    <p>Autoimmune destruction of the gastric parietal cells</p> Signup and view all the answers

    What is the effect of B12 deficiency on the utilization of methyl-THF for the conversion of homocysteine to methionine?

    <p>Impaired utilization leading to accumulation of methyl-THF</p> Signup and view all the answers

    What is the main cause of hyperhomocysteinemia and homocystinuria in vitamin B12 deficiency?

    <p>Failure to metabolize homocysteine</p> Signup and view all the answers

    What is the consequence of B12 deficiency on the THF forms needed in cell division?

    <p>Deficiency of the THF forms</p> Signup and view all the answers

    What is the likely cause of megaloblastic anemia in vitamin B12 deficiency?

    <p>Impaired utilization and accumulation of methyl-THF</p> Signup and view all the answers

    What is the main cause of vitamin B12 deficiency due to a decrease in intrinsic factor (IF)?

    <p>Autoimmune destruction of the gastric parietal cells</p> Signup and view all the answers

    What is the rare cause of vitamin B12 deficiency, except among vegetarians?

    <p>Dietary causes</p> Signup and view all the answers

    What is the primary manifestation of vitamin B12 deficiency known as pernicious anemia?

    <p>Megaloblastic anemia</p> Signup and view all the answers

    What is the consequence of B12 deficiency on the utilization of methyl-THF for the conversion of homocysteine to methionine?

    <p>Impaired utilization of methyl-THF</p> Signup and view all the answers

    What effect does B12 deficiency have on the THF forms needed in cell division?

    <p>Deficiency of THF forms</p> Signup and view all the answers

    Study Notes

    • Vitamin B12 deficiency causes: Malabsorption, Gastrectomy, Autoimmune destruction of gastric parietal cells (decrease of IF), Rare dietary deficiency among vegetarians
    • Vitamin B12 deficiency symptoms: Pernicious anemia - Megaloblastic anemia (folate trap in methyl-THF form), Neurological manifestations, Hyperhomocysteinemia and homocystinuria, Methylmalonic aciduria
    • Folate Trap Hypothesis: B12 deficiency impairs utilization of methyl-THF for homocysteine conversion, leading to a deficiency of THF forms needed in cell division, most notably in rapidly dividing cells like erythropoietic cells of bone marrow, causing megaloblastic anemia.

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    Description

    Test your knowledge on the causes and manifestations of vitamin B12 deficiency. Learn about malabsorption, gastrectomy, autoimmune destruction, and dietary causes as well as the manifestations such as pernicious anemia, neurological manifestations, hyperhomocysteinemia, and methylmalonic aciduria.

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