Vitamin B12 and Anemia Quiz

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Questions and Answers

What is the correct name for the vitamin B12 deficiency anemia?

  • Megaloblastic Anemia
  • Periorbital Anemia
  • Pernicious Anemia (correct)
  • Macrocytic Anemia

What is the function of vitamin B12 that makes it important for the prevention of anemia?

  • It is a vital component of the electron transport chain in mitochondria.
  • It plays a crucial role in DNA synthesis and cell division. (correct)
  • It is a key component of coenzyme A, crucial for carbohydrate metabolism.
  • It assists in the conversion of phenylalanine to tyrosine.

Which of the following is NOT a cause of non-megaloblastic macrocytic anemia?

  • Liver dysfunction
  • Folate deficiency (correct)
  • Myelodysplastic Syndrome
  • Alcoholism

What is the minimum value of MCV (Mean Corpuscular Volume) for a patient to potentially be diagnosed with macrocytic anemia?

<p>100fL (B)</p> Signup and view all the answers

What are the primary sources of dietary vitamin B12? (Select all that apply)

<p>Dairy products (B), Meat and fish (C)</p> Signup and view all the answers

What is the typical treatment regimen for pernicious anemia?

<p>Intramuscular injection of Vitamin B12 (B)</p> Signup and view all the answers

What is the common characteristic feature of megaloblastic anemias?

<p>Increased red blood cell size (B)</p> Signup and view all the answers

Which of the following is NOT a known cause of folate deficiency?

<p>Increased production of red blood cells (B)</p> Signup and view all the answers

Which of the following tests is NOT typically used to diagnose alcoholism in a patient with macrocytosis?

<p>Complete Blood Count (C)</p> Signup and view all the answers

How does hypothyroidism contribute to the development of anemia?

<p>Reducing the production of erythropoietin (A)</p> Signup and view all the answers

What is the primary mechanism by which certain drugs can cause anemia?

<p>Interfering with folate or vitamin B12 metabolism (D)</p> Signup and view all the answers

What is the recommended serum folate level for diagnosing folate deficiency?

<p>2 ng/mL (A)</p> Signup and view all the answers

What is the primary role of methylmalonic acid in the context of vitamin B12 deficiency?

<p>It is a marker for vitamin B12 deficiency (A)</p> Signup and view all the answers

What role does intrinsic factor play in the absorption of vitamin B12?

<p>Intrinsic factor binds to vitamin B12 and facilitates its absorption in the small intestine. (A)</p> Signup and view all the answers

What is the primary function of vitamin B12 in the body?

<p>Vitamin B12 is involved in the production of red blood cells and the synthesis of DNA. (B)</p> Signup and view all the answers

Identify the primary site of vitamin B12 absorption in the digestive tract.

<p>Terminal Ileum (C)</p> Signup and view all the answers

Which of the following is NOT a common neurological symptom associated with vitamin B12 deficiency?

<p>Hyperreflexia (B)</p> Signup and view all the answers

What is the relationship between folic acid and vitamin B12 in the body?

<p>Vitamin B12 is required to convert folic acid to its active form, 5-methyltetrahydrofolate, which is crucial for DNA synthesis. (C)</p> Signup and view all the answers

Which of the following laboratory findings is NOT consistent with megaloblastic anemia caused by vitamin B12 deficiency?

<p>Increased serum ferritin levels (A)</p> Signup and view all the answers

What is the significance of hypersegmented neutrophils in a peripheral blood smear?

<p>Hypersegmented neutrophils indicate a deficiency in vitamin B12 or folic acid. (C)</p> Signup and view all the answers

Which of the following is NOT a potential cause of vitamin B12 deficiency?

<p>Hyperthyroidism (B)</p> Signup and view all the answers

Why is homocysteine elevated in both B12 and folate deficiency?

<p>Both B12 and folate are required for the conversion of homocysteine to methionine. (C)</p> Signup and view all the answers

Which of the following is NOT a possible cause of a low reticulocyte count in a patient with both normal B12 and folate levels?

<p>Hemolysis (C)</p> Signup and view all the answers

Which of the following biochemical tests is NOT typically used to rule out hemolysis?

<p>Creatinine kinase (A)</p> Signup and view all the answers

A patient has a hematocrit of 35% and a red blood cell count of 5.0 x 10^6 cells/uL. What is their MCV and what type of anemia do they have?

<p>MCV = 70 fL, Microcytic anemia (D)</p> Signup and view all the answers

A patient has a hemoglobin of 12.5 g/dL, a hematocrit of 42%, and a red blood cell count of 4.2 x 10^6 cells/uL. Calculate the MCHC. What is the diagnosis based on the MCHC and the MCV you calculate?

<p>MCHC = 30.8 g/dL, Normocytic anemia (D)</p> Signup and view all the answers

A patient has a hemoglobin of 12.5 g/dL, a hematocrit of 37%, and a red blood cell count of 4.2 x 10^6 cells/uL. What is their MCV and MCHC, and what type of anemia do they have?

<p>MCV = 88 fL, MCHC = 29.8 g/dL, Normocytic anemia (B)</p> Signup and view all the answers

Which of the following statements accurately describes the relationship between B12, folate, and homocysteine?

<p>Both B12 and folate are involved in the conversion of homocysteine to methionine, so deficiencies in either can lead to elevated homocysteine levels. (C)</p> Signup and view all the answers

A patient has a high reticulocyte count and normal B12 and folate levels. Which of the following is the most likely cause?

<p>Hemolysis or blood loss (D)</p> Signup and view all the answers

Flashcards

Macrocytic Anemia

A type of anemia characterized by larger than normal red blood cells (MCV > 100 fL).

Etiology

The causes or origins of a disease, in this case, macrocytic anemia.

Megaloblastic Anemia

A type of macrocytic anemia caused by vitamin B12 or folate deficiency.

Vitamin B12 Sources

Food sources of vitamin B12 include meat, fish, dairy products, and eggs.

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Non-Megaloblastic Anemia

A form of macrocytic anemia not caused by vitamin deficiencies; includes causes like liver dysfunction and alcohol use.

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Vitamin B12 Function

Essential for DNA synthesis and neurological function.

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Intrinsic Factor

A protein secreted by gastric parietal cells that binds B12 for absorption.

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Terminal Ileum Absorption

The site in the intestine where Vitamin B12 is absorbed.

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Folic Acid Activation

Converted to its active form by B12 to assist in DNA synthesis.

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Hypersegmented Neutrophils

Neutrophils with six or more lobes, indicative of B12 deficiency.

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Macro-ovalocytes

Large, oval-shaped red blood cells present in B12 deficiency.

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Lab Finding: LDH

High levels indicate hemolysis in Vitamin B12 deficiency.

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Haptoglobin Levels

Decreased haptoglobin levels are seen with hemolysis, as it binds free hemoglobin.

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Pernicious Anemia

A type of megaloblastic anemia caused by the lack of intrinsic factor, leading to vitamin B12 deficiency.

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Antigastric Parietal Cell Autoantibodies

Autoantibodies that target gastric parietal cells, indicating pernicious anemia.

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Folate

Also known as folic acid, it is a B vitamin essential for red blood cell production.

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Folate Absorption Site

Folate is absorbed in the upper jejunum of the intestine by passive and active diffusion.

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MCV in Non-Megaloblastic Anemia

Mean corpuscular volume (MCV) ranges from 100-110 fL in non-megaloblastic anemia cases.

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Diagnostic Tests for Alcoholism

Tests like Michigan Alcoholism Screening Test and Y-glutamyltransferase level help diagnose alcoholism in macrocytosis.

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Homocysteine and B12

Vitamin B12 is needed to convert homocysteine to methionine. Low B12 levels lead to high homocysteine.

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Reticulocyte Count Interpretation

High reticulocyte count indicates hemolysis or blood loss; low suggests other conditions like alcoholism.

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Biochemical Tests for Hemolysis

Tests like lactate dehydrogenase, indirect bilirubin, and haptoglobin help exclude hemolysis.

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Mean Corpuscular Volume (MCV)

MCV measures the average size of red blood cells; helps classify anemia as macrocytic, microcytic, or normocytic.

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Macrocytic Anemia Diagnosis

Characterized by MCV > 100 fL; indicates larger red blood cells, commonly due to B12 or folate deficiency.

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Microcytic Anemia Diagnosis

Characterized by MCV < 80 fL; indicates smaller red blood cells, often due to iron deficiency.

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Normocytic Anemia Diagnosis

MCV between 80-100 fL; indicates normal size red blood cells but low counts, often due to chronic diseases.

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Red Cell Indices Calculation

MCH, MCHC, and MCV are calculated to assess red blood cell size and hemoglobin concentration in anemia cases.

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Study Notes

Macrocytic Anemia

  • Macrocytic anemia is characterized by a high Mean Corpuscular Volume (MCV)
  • Anemia is defined as a hemoglobin (Hb) level below normal
    • Male: <13.94 g/L
    • Female:<11 g/L
  • MCV is greater than 100 fL

Etiology of Macrocytic Anemia

  • Two main categories:
    • Megaloblastic
      • Vitamin B12 deficiency/impairment of utilization
      • Folate deficiency/impairment of utilization
      • Liver dysfunction
      • Some drug usage
    • Non-megaloblastic
      • Alcoholism
      • Myelodysplastic syndrome (MDS)
      • Hypothyroidism

Megaloblastic Anemia - Vitamin B12 Deficiency

  • Sources: Meat, fish, eggs, dairy products
  • Also known as pernicious anemia
  • Function: RBC formation, DNA synthesis, maintaining neurological function
  • Causes:
    • Dietary deficiency
    • Malabsorption
    • Congenital disorders
    • Gastrectomy

Vitamin B12 Absorption

  • Vitamin B12 binds to intrinsic factor (IF) secreted by gastric parietal cells
  • Absorbed in the terminal ileum
  • Once absorbed, it acts as a coenzyme to produce methionine (from homocysteine)
  • Folic acid is converted to its active form (5-methyltetrahydrofolate)
  • Impairs DNA synthesis

Sign and Symptoms

  • Fatigue
  • Headache
  • Palpitations
  • Dyspnea
  • Gray hair
  • Neurological symptoms (e.g., paresthesia, hypoesthesia)

Peripheral Blood

  • Microscopic Observation
    • Presence of hypersegmented neutrophils (more than 6 lobes)
    • Macro-ovalocytes
    • Anisocytosis
  • Bone Marrow Biopsy
    • Hypercellularity with abnormal maturation of myeloid cell lines.

Blood Smear

  • Hypersegmented RBCs
  • Macrocytosis

Laboratory Findings

  • Biochemical results (evidence of hemolysis)
    • High Lactate dehydrogenase (LDH) level
    • High indirect bilirubin level
    • Decreased haptoglobin level
  • Treatment: Parenteral administration of vitamin B12, restoring hematological levels to normal within a month.

Megaloblastic Anemia - Pernicious Anemia

  • Characteristic:
    • Lack of intrinsic factor
    • Destruction of gastric parietal cells
    • Detection of antigastric parietal cell autoantibodies
  • Treatment: Lifelong administration of vitamin B12 (intramuscular injection and high oral doses).

Pernicious Anemia - Vitamin B12 Absorption Failure

  • In normal conditions, B12 is absorbed from the gut.
  • In pernicious anemia, the parietal cells fail to secrete intrinsic factor (IF), preventing B12 absorption.

Megaloblastic Anemia - Folate Deficiency

  • Folate is also known as folic acid or folacin
  • Sources: Green vegetables and animal products
  • Absorbed in the upper jejunum via passive and active diffusion
  • Causes:
    • Nutritional deficiency
    • Malabsorption
    • Medication
  • Treatment: Oral folic acid for nutritional deficiencies

Role of Vitamin B12 and Folate in DNA Synthesis

  • Detailed steps involved in the sequential reactions of folate and B12 in the synthesis of DNA.

Non-megaloblastic Anemia - Alcoholism

  • MCV: 100-110 fL
  • Diagnosis: Michigan Alcohol Screening Test, γ-glutamyltransferase level

Non-megaloblastic Anemia - Hypothyroidism

  • Thyroid hormone stimulates the production of erythropoietin, impacting hematopoiesis
  • Reduction of thyroid hormone causes anemia

Non-megaloblastic Anemia - Drugs

  • Interference with the absorption, plasma transport, or delivery of folate or vitamin B12
  • Example drugs: Hydroxyurea, Methotrexate, Zidovudine.

Differential Diagnosis

  • High MCV:

    • B12 deficiency (serum B12 < 200 pg/mL)
    • Folate deficiency (serum folate < 2 ng/mL)
    • B12 (200-300), check methylmalonic acid (relationship to B12).
    • Elevated homocysteine (conversion to methionine reliant on B12- low levels associated with high homocysteine)

  • Check reticulocytes, elevated= hemolysis/blood loss; low = alcoholism, hypothyroidism, MDS, liver disease

  • Check Lactate dehydrogenase, Indirect bilirubin, Haptoglobin (for hemolysis suspicion)

Calculating MCV

  • MCV calculation formula: (Hct X 10)/RBC
  • Different MCV values result in different diagnoses

Calculating Red Cell Indices

  • Formulae and examples given for calculating red cell indices (MCV, MCH, MCHC) using hematocrit, hemoglobin and red cell values.
  • Corresponding diagnoses are provided.

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