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7. Haematology > Macrocytic Anaemia > Flashcards

Macrocytic Anaemia Flashcards

1
Q

List 3 causes of macrocytic anaemia.

A
  1. B12 deficiency
  2. Folate deficiency.
  3. Alcohol excess.
  4. Liver disease.
  5. Hypothyroidism.
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2
Q

Where is B12 absorbed?

A

The terminal ileum.

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3
Q

Briefly explain how B12 is absorbed.

A

1) B12 released from food in stomach by peptic acid.

2) Parietal cells @ gastric fundus produce intrinsic factor (IF).

3) IF binds B12.

4) IF-B12 complex travels to terminal ileum.

5) Endocytosis - complex gets bound to transcobalamin, which is then released into blood stream.

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4
Q

List some possible causes of B12 deficiency anaemia.

A

1) Poor diet - veggie, vegan, old age.

2) Decreased gastric breakdown - gastric surgery, atrophic gastritis.

3) Malabsorption - pernicious anaemia, Crohn’s, coeliac.

4) Drugs - metformin (decreases absorption), PPI/H2 antagonists.

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5
Q

What causes pernicious anaemia?

A

Autoimmune atrophic gastritis - autoantibodies against parietal cells and intrinsic factor.
Leading to achlorhydria (reduced HCL acid production) and B12 malabsorption.

Associated with other AI disease - thyroid, vitiligo, DM.

Risk of gastric cancer.

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6
Q

Explain how pernicious anaemia leads to B12 deficiency.

A

Pernicious anaemia leads to a loss of parietal cells -> reduced intrinsic factor production -> vitamin B12 malabsorption.

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7
Q

Give 3 signs for pernicious anaemia.

A
  1. Progressively increasing symptoms of anaemia e.g. fatigue, dyspnoea, palpitations, tachycardia
  2. Pallor + mild jaundice = lemon-tinged skin colour
  3. Red sore tongue (glossitis) may be present
  4. Angular stomatitis/cheilosis (ulceration of the corners of the mouth) may be present
  5. Headache is hallmark of megaloblastic anaemia.
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8
Q

What neurological signs + symptoms do you see in very low levels of B12 in B12 deficiency?

A
  • Symmetrical paresthesia (burning or prickling pain, tingling) in fingers and toes
  • Ataxia + loss vibration (posterior column degeneration)
  • Peripheral neuropathy
  • Dementia
  • Psychosis
  • Peripheral neuropathy

Triad of - upgoing plantars, loss of knee jerk, loss of ankle jerk.

Mainly - peripheral neuropathy - symmetrical paraesthesia

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9
Q

What specific tests/investigations would you perform if you suspected pernicious anaemia?

A
  1. Blood count & film:
    * Typical of megaloblastic anaemia
    * RBC’s are MACROCYTIC
    * Peripheral film shows oval macrocytes (large RBC’s) with hyper-segmented neutrophil polymorphs with six or more lobes in the nucleus
  2. Serum bilirubin may be raised
    * As a result of ineffective erythropoiesis, resulting in increased RBC breakdown
  3. Serum B12 is low
  4. Hb is low
  5. Reticulocyte count is LOW
  6. Intrinsic factor antibodies - DIAGNOSTIC but lower sensitivity i.e. not present in all patients
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10
Q

How do you treat pernicious/B12 deficient anaemia?

A

Symptomatic + severe = IM hydroxycobalamin 1mg alternate days till no further improvement, then 1mg every 2/12

Moderate (no neuro involvement) = IM hydroxycobalamin 1mg 3x/week for 2 weeks, then every 3/12 - lifelong

IM = because no point giving it orally - not going to be absorbed

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11
Q

Where is folate absorbed and what are its sources?
What about B12?

A

Folate = proximal jejunum + duodenum.
Green veg, nuts, liver.

B12 = ileum (combines with intrinsic factor).
Meat, fish and dairy.

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12
Q

How does B12/folate deficiency lead to anaemia?

A

B12 and folate needed for DNA synthesis - developing red cells can’t divide.

They are stuck as large immature cells (megaloblastic), which then become macrocytic RBCs.

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13
Q

Give some causes of folate deficiency

A
  1. Poor diet/intake - poverty, alcoholics and elderly.
  2. Increased demand - pregnancy or increased cell turnover.
  3. Malabsorption - Coeliac, Crohn’s.
  4. Drugs, alcohol, MTX (inhibits folic acid synth).
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14
Q

What symptoms might help you differentiate between macrocytic anaemia due to Folate vs B12 deficiency?

A

B12 deficiency: you get peripheral neuropathy and neuropsychiatric complaints.

Folate deficiency: you don’t.

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15
Q

How would you investigate folate-deficiency anaemia?

A
  1. Blood count:
    * Typical of megaloblastic anaemia
    * RBC’s are MACROCYTIC
  2. Blood film:
    * Oval macrocytes (large RBC’s)
    * Hyper-segmented neutrophil polymorphs with ≥6 lobes in the nucleus
  3. Serum and red cell folate is LOW
  4. GI investigation
    e.g. small bowel biopsy to exclude occult GI disease
  5. Serum bilirubin may be raised
    - As a result of ineffective erythropoiesis, resulting in increased RBC breakdown
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16
Q

Describe the treatment of folate-deficiency anaemia.

A
  1. Treat underlying cause
  2. Folic acid tablets orally daily for 4 months (1-5 mg)
    * Always give alongside B12 → folate in presence of B12 deficiency may cause significant neurological disease

If pancytopaenia present as well: consider packed RBC transfusion.

7. Haematology (15 decks)

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