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Haematology > Megaloblastic Anaemias > Flashcards

Megaloblastic Anaemias Flashcards

1
Q

What can a Macrocytic anaemia be sub catagorised into?

A
  • Megaloblastic anaemia (resulting from impaired DNA synthesis, preventing the cells from dividing normally. Rather than dividing, they grow into large, abnormal cells.)
    or
  • A Normoblastic Macrocytic Anaemia.
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2
Q

What are some causes of a Megaloblastic anaemia?

A

B12 deficiency
Folate Deficiency
Others (drugs, Rare Inherited abnormalities)

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3
Q

What kind of Diet leads to a Vitamin B12 deficiency?

A

Low dietary intake via Veganism.

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4
Q

How does a B12 deficiency cause a megaloblastic anaemia?

A

Pernicious Anaemia:
- Autoimmune condition with resulting destruction of the Gastric Parietal cells.
- This results in an intrinsic factor deficiency with B12 malabsorption.

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5
Q

What condition is Pernicious anaemia often associated with?

A

Atrophic Gastritis.

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6
Q

How does a Folate deficiency occur?

A
  • Inadequate intake (found in leafy green veg)
  • Malabsorption
  • Excess utilisation - haemolysis, exfoliating dermatitis, pregnancy, malignancy.
  • Anticonvulsant drugs.
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7
Q

What is a Megaloblast?

A

An abnormally large nucleated red cell precursor with an immature nucleus.

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8
Q

Why do megaloblastic anaemias have a lack of red cells?

A

Due to predominant defects in DNA synthesis in developing precursor cells (megaloblasts) in the marrow.

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9
Q

What happens to the megaloblasts as a result of the defect in DNA synthesis?

A

Division of maturing megaloblasts is reduced and apoptosis is increased.

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10
Q

What happens when the Hb content of a megaloblast reaches optimum level?

A

The Nucleus is extruded, leaving behind a bigger than normal red cell i.e. a macrocyte.

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11
Q

What are B12 and folate essential for?

A

DNA synthesis and nuclear maturation (e.g. blood cell effect)
AND
DNA modification and gene activity (e.g. nervous system)

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12
Q

Where is Folate absorbed in the body?

A

Duodenum and Jejunum

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13
Q

Where is B12 absorbed in the body?

A

Ileum.

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14
Q

How long can folate stores last?

A

4 months

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15
Q

How long can B12 stores last?

A

2-4 yrs.

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16
Q

How is B12 released from Protein complexes in food (at the start of its metabolism)?

A

Vit B12 is liberated from protein complexes in food by gastric enzymes and then binds to a Vitamin B12-binding protein (R-Binder)

17
Q

How does Vitamin B12 get released from the R binder?

A

By Pancreatic Enzymes

18
Q

What does B12 become bound to after its been seperated from the R-Binder by pancreatic enzymes?

A

Intrinsic factor.

19
Q

What is Intrinsic factor and where is it secreted from?

A

It is a Glycoprotein which is secreted from the gastric parietal cells.

20
Q

Where does the Intrinsic factor take B12 once they have become bound?

A

to a specific receptor on the mucosa of the ileum.

21
Q

What happens to B12 once it has been brought to the Receptors on the Ileum?

A

It enters the Ileal cells. (intrinsic factor remains in the lumen and is excreted)

22
Q

How is Vitamin B12 transported from the enterocytes to the bone marrow?

A

By Glycoprotein transcoalbamin 2

23
Q

How is Folate absorbed from dietary folate?

A

Dietary folate is converted to monoglutamate which is absorbed in the jejunum.

24
Q

What neurological problems can present with B12 deficiency?

A
  • Posterior / Dorsal column abnormalities.
  • neuropathy
  • Dementia
  • Psychiatric manifestations.
25
Q

What can be seen on the bloodfilm of patients with a Megaloblastic anaemia?

A

Macroovalocytes and “hyeprsegmented” neutrophils. (normally 3-5 nuclear segments)

26
Q

What are Macroovalocytes?

A

Macroovalocytes are enlarged, oval-shaped erythrocytes (red blood cells)

27
Q

What Autoantibodies can be checked for in a Megaloblastic anaemia?

A
  • Anti Gastric-parietal cell (sensitive not specific)
  • Anti intrinsic factor (Specific, not sensitive)
28
Q

What is the management of a Megaloblastic anaemia?

A

Treat the underlying cause where possible.
Vitamin B12 injections for life in pernicious anaemia.
Folic acid tablets 5mg/day PO.
Red cell transfusions - only in potentially life-threatening anaemia.

29
Q

What are some causes of a normoblastic macrocytosis?

A
  • Alcohol
  • Liver disease
  • Hypothyroidism
  • Marrow failure (will be assoc with anaemia)
    (e.g. - Myelodysplasia, Myeloma, Anaplastic Anaemia)
30
Q

What is Spurious Macrocytosis?

A

A macrocytosis where the volume of mature red cells is normal but the MCV has been measured as high.

31
Q

What can cause a Spurious Macrocytosis?

A
  • Reticulocytosis
  • Cold-agglutinins (cause RBCs to clump at temperatures lower than core body Temp. making them appear as one giant cell.) - Make sure sample is warmed to 37 degrees.

Haematology (10 decks)

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