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Year 2 - MCD Haem > B12 & Folate Deficiencies > Flashcards

B12 & Folate Deficiencies Flashcards

1
Q

General role of Vitamin B12 and folate?

A

Required for DNA Synthesis!

Absence leads to severe anaemia - can be fatal

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2
Q

What is Vit B12 required for?

A

o DNA Synthesis

o Integrity of NS

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3
Q

What is folic acid required for?

A

o DNA Synthesis
- to get from dUMP –> dTMP need a methyl group which is indirectly provided by diertary folate

o Homocystine metabolism

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4
Q

Overall principal of the clinical features shown by vit B12 and folate deficiency?

A

ALL rapidly dividing cells are affected
i.e. bone marrow, epithelial surface of mouth & gut, gonads, embryos

This means the clinical features of B12 and folate deficiency will be BROAD

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5
Q

Clinical features of B12 and folate deficiency?

A

Anaemia
- weak, tired, SOB

Jaundice
- due to breakdown of RBCs

Glossitis
- inflammation of tounge

Angular cheiolosis
- red swollen patches at corner of mouth

Weight loss and change of bowel habit
- as affects rapidly dividing cells of the gut

Sterility
- affects rapidly dividing sperm cells

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6
Q

What is different about B12 and folate deficiency to iron deficiency anaemia?

A

Associated with
o LARGER RBCs - macrocytic
o LARGE MCV - megaloblastic

Hence macrocytic & megaloblastic anaemia!

  • macrocytic
    (average RBC size has increased)
  • megaloblastic
    (morphological change in RBC precursors within the bone marrow)
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7
Q

What can give rise to macrocytic anaemia?

A

o Vit B12/folate deficiency (oval macrocytes)

o Liver disease (round macrocytes)

o Hypothyroidism

o Drugs that interfere w. DNA synthesis (e.g. azathioprine)

o Haematological Disorders

  • Myelodysplasia (production of one/all blood cells by bone marrow is disrupted)
  • Aplastic anaemia
  • Reticulocytosis
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8
Q

Megalobastic?

A

Morphological change in RBC precursors within the bone marrow

Remember - it is CONFINED to changes in the BONE MARROW

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9
Q

Normal RBC maturation?

A
  1. Erythroblast (RBC precursor)
  2. Normoblast (early, intermediate, late)
  3. Reticulocyte (has lost its nucleus at this point)
  4. RBC

Colour change quite a lot:
Basophilic (blue) TO polychromatic TO RBC pink
o the more DNA you have = more blue
o the most Hb you have = more pink

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10
Q

How do you determine if the cells in a lineage are normal?

A
  1. Chromatin and how open it is
    o open in megalobastic cells
  2. Colour of the cytoplasm and how blue it is
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11
Q

How do you recognise megaloblastic anaemia?

A

ASYNCHRONOUS maturation of the nucleus and cytoplasm in the erythroid (RBC) series

i.e. nucleus does NOT mature but cytoplasm does (as cannot synthesise DNA properly)

SO
o nucleus seen in a pink RBC (should NOT see a nucleus)
o maturing RBCs seen in the bone marrow

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12
Q

How will peripheral blood appear in megalobastic anaemia?

A
  1. Anisocytosis
    - variation in size of RBCs
  2. Large RBCs
  3. Hypersegmented neutrophils
  4. Giant metamyelocytes
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13
Q

Thyroid disease can be a cause of megaloblastic RBCs?

T/F

A

FALSE!

Causes RBCs to be large so MACROCYTIC

NOT megaloblastic

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14
Q

3 tests that you would do if someone had a macrocytosis?

A
  1. Blood test
    o folate, iron, B12
  2. Thyroid function test
  3. Reticulocyte count
    o and blood film
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15
Q

If someone has hypersegmented neutrophils, what are the 2 possible clinical disorders?

A
  1. Megaloblastic anaemia - B12 anaemia

2. Megaloblastic anaemia - folate deficiency

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16
Q

How is folate found in the diet and what can ruin it?

A

Freshy leafy veg

Destroyed by overcooking/canning/processing

17
Q

Potential causes of folate deficiency?

A 
1. Decrease intake
 o ignorance
 o poverty
 o apathy
 o alcoholics and elderly (may not make as much effort)
2. Increased demand!
o PHYSIOLOGICAL (pregnancy, adolescence, premature babies)
o PATHOLOGICAL (malignancy, erythoderma, haemolytic anaemia)
18
Q

Typical classical case that can be seen for folate deficiency?

A
  • Alcoholic admitted w. a head injury after a fight
  • 30yr old with infected whole body eczema (erythoderma)
  • 90yr old lady who has a cup of tear and a jam sandwich for each meal
19
Q

How do you diagnose folate deficiency?

A
  1. Laboratory diagnosis
    o FBC and film
    o folate levels in the blood
  2. Assessment
    o history
    o examination (skin disease, alcoholic liver diesase)
20
Q

What are the consequences of folate deficiency?

A
  1. Megaloblastic, macrocytic anaemia
  2. Neural tube defects in developing fetus
  • spina bifida, anencephaly
  • all pregnant women take folic acid (0.4mg) prior to conception & for first 12 weeks
  1. Increased risk of thrombosis in association with variant enzymes invovled in HOMOCYSTEINE METABOLISM
  • if homocysteine levels build up, increased risk of atherosclerosis and premature vascular disease
  • if mildly elevated, still associated w. CVD, arterial/vernous thrombosis
21
Q

What are the consequences of B12 deficiency?

A 
Neurological problems
 o bilateral peripheral neuropathy
 o subacute combined degeneration of the cord (can cause paralysis)
 o optic atrophy
 o optic atrophy
 o dementia
22
Q

What can be identified in the history of those w B12 deficiency?

A 
o Paraesthesia (tingling feeling)
o Muscle weakness
o Difficultly walking
o Visual impairment
o Psychiatric disturbance
23
Q

During examination of B12 deficiency, what will be seen?

A

Absent reflexes
AND
upgoing plantar responses

i.e. combination of UPPER & LOWER motor neuron signs

24
Q

Causes of B12 deficiency?

A
  1. Poor absorption

Complex method of absorption that can go wrong
o Method 1 - through duodenum (slow and inefficient) (1%)
o Method 2 - B12 combines w. IF and the binds to ileum receptors (99%)
(so 3 things essential - intact stomach, IF and a functional S.I)

  1. Reduced dietary intake
    o stores are large and last for years
    o found in all animal produce
    o vegans are at risk
  2. Infections/infestations
    o abnormal bac. flora
    o tropical sprue
    o fish tapeworm
25
Q

Main reason for impaired B12 absorption?

A

Reduction in Intrinsic Factor (IF)

o Post gastrectomy
o Gastric atrophy
o Pernicious anaemia - autoimmune condition associated w. a severe lack of IF

26
Q

Pernicious anaemia?

A

Autoimmune condition associated w. a severe lack of IF

o Males have a decreased life expectancy as have stomach Ca

There is either a presence of:
o IF-Abs - occasionally found in other condtions
o Parietal cell Abs

27
Q

Other possible reasons for impared B12 absorption?

A
  1. Diseases of small bowel (& terminal ileum)
    e. g. Crohn’s, Coeliac disease, Surgical resection
  2. Infections/infestations
    e. g. H.pylori, fish tapeworm, bac. overgrowth
  3. Drugs
    e. g. Metformin, PPIs (proton pump inhibitors), oral contraceptive pill
28
Q

To diagnose patients w. low B12, what can we measure?

A
  1. Abs to parietal cells & IF
  2. Abs for coeliac disease
  3. Breath test for bacterial overgrowth
  4. Stool test for H.pylori
  5. Test for Giardia
  6. Olden days had SHILLING TEST
29
Q

Explain the Shilling Test

A

Prior to test, replenish the stores

PART 1:

a) injection of B12 to saturate stores
b) drink radiolabelled B12
c) measure excretion in urine

Would normally except it to come out in the urine AS SORES ARE FULL!

If none is in the urine, several possibilites:
o Not absorbing B12
- pernicious anaemia, small bowel disease
o Haven’t corrected B12 deficiency before test

PART 2:

a) repeat test
b) BUT with the addition of IF
c) measure excretion in the urine

RESULTS:
IF Part 1 - LOW & Part 2 - NORMAL
o pernicious anaemia w. auto-Abs to the B12

30
Q

If see a classic case BUT with normal B12 what would you do?

A

Could still lead to B12 neurological deficits
SO
would treat this as a B12 deficiency (to be safe) and send markers off to be assessed

Measure:
o methylmalonyl acid
o homocysteine
o look for anti-IF Abs

31
Q

Treatment for B12 deficiency?

A

o Injections of B12

  • 1000ug (i.m)
  • 3x/week for 2 weeks
  • thereafter every 3months

If neurological involvement
o B12 injections alternate days UNTIL no further improvements (up to 3weeks)
o thereafter every 2months

32
Q

A 49 y old man with grey hair and blue eyes presents with anaemia. His blood count is as follows:
Hb 90g/l WBC 4 x 109/l platelets 160 x 109/l MCV 110fl

Which would be the most appropriate set of investigations
A. Blood film, liver function, Shilling test
B. Folate, B12, thyroid function, liver function
C. Thyroid function, B12 and anti-intrinsic factor antibodies
D. Ferritin, shilling test, folate
E. Blood film, thyroid antibodies, anti-parietal cell antibodies

A

B

 The MCV is high and so not sure of the cause of macrocytic anaemia.
 Shillings test you would only do in someone with a known B12 deficiency.
 B is the best answer as its exactly what you would do in someone with a raised MCV.
o C misses’ folate and you wouldn’t need to do intrinsic antibodies until you know their B12 deficient.
 D isn’t right as it has ferritin (only do if they have low MCV).

33
Q

Classic cases of B12 deficiencies?

A 
FIRST CASE: 
o 40 y old female with tingling in fingers
o Hb 10g/dl and MCV 105
o Family history of auto-immune disease
o MEASURE VITAMIN B12 and it is low
SECOND CASE:
o Patient with an inflamed tongue (glossitis)
o Premature grey hair
o falls over when they close their eyes
o Loss of proprioception
   = Romberg’s sign

Year 2 - MCD Haem (11 decks)

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