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notes to flashcards year 2 - MCD > B12 and folate def > Flashcards

B12 and folate def Flashcards

1
Q

what is it B12 required for?

A
  • DNA synthesis

- integrity of immune system

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2
Q

what is folic acid required for?

A
  • DNA synthesis (dUMP –> dTMP needs methyl group from folate)
  • homocystine metabolism
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3
Q

what cells are affected in B12 and folate def?

A
  • all rapidly dividing cells affected

- i.e. bone marrow, epithelial surfaces of gut gonads, embryos

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4
Q

what are the clinical features of B12 and folate def?

A
  • anaemia
  • jaundice
  • glossitis
  • angular cheilosis (red swollen patches at corner of mouth)
  • sterility (affects rapidly dividing sperm cell)
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5
Q

describe the red cells when there is a deficiency of B12 or folate

A
  • LARGE red cells
  • LARGE MCV
  • macrocytic and megaloblastic anaemia
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6
Q

what does megaloblastic mean?

A
  • morphological change in RBC precursors within bone marrow
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7
Q

what else can cause macrocytic anaemia?

A
  • liver disease
  • hypothyroidism
  • drugs
  • haematological disorders
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8
Q

describe normal RBC maturation

A
  • erythoblast
  • normoblast
  • reticulocyte
  • RBC
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9
Q

what is the colour change during RBC maturation?

A
  • basophilic (blue)
  • polychromatic
  • RBC pink
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10
Q

what is megaloblastic anaemia?

A

asychronous maturation of nucleus and cytoplasm in erythoid series

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11
Q

in megaloblastic anaemia, what is the appearance of peripheral blood?

A
  • anisocytosis
  • large RBCs
  • hypersegmented neutrophils
  • giant metamyelocytes
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12
Q

if someone has macrocytosis, what are some tests you can do?

A
  • blood test (folate, iron, B12)
  • thyroid function test
  • reticulocyte count and blood film
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13
Q

why do you do a thyroid function test?

A
  • thyroid disease causes a macrocytosis and not a megaloblastic anaemia
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14
Q

what are the 2 possible clinical disorders that cause a hypersegmented neutrophil?

A
  • B12/folate def
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15
Q

where is folate present?

A
  • fresh leafy veg

- destroyed by overcooking/canning/processing

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16
Q

what are the causes of folate def?

A
  • dec. intake

- inc. demand (physiological = pregnancy, adolescence, premature babies. Pathological = malignancy, HA)

17
Q

what are the consequences of folate def?

A
  • megaloblastic, macrocytic anaemia
  • neural tube defects in developing foetuses
  • inc, risk of thrombosis
18
Q

consequences of B12 def?

A
  • neurological problems (bilateral peripheral neuropathy)
  • paraesthesia
  • muscle weakness
  • difficult walking
  • visual impairment
  • psychiatric disturbance
19
Q

what would you see in an exam of someone with B12 def?

A
  • absent reflexes and upgoing plantar responses

- combo of upper and lower motor neuron signs

20
Q

what are the causes of B12 def?

A
  • poor absorption
  • reduced dietary intake (difficult for this as stores are large)
  • infections
21
Q

what are the 2 methods of absorption of B12?

A
  1. 1%: slow and inefficient absorption through duodenum

2. 99%: B12 combines with IF and this binds to Ileum receptors in ileum

22
Q

what causes impaired B12 absorption?

A
  • reduction in IF (post gastrectomy, gastric atrophy, Pernicious anaemia)
  • diseases of small bowel (Chron’s, coeliac, surgical resection)
  • infections/infestations (H. Pylori, giardia)
  • drugs (metformin, the pill, PPIs)
23
Q

what is pernicious anaemia?

A

AI condition ass/ w/ severe lack of intrinsic factor

24
Q

what is there a presence of in PA?

A
  • Intrinsic factor antibodies: occasionally found in other conditions
  • parietal cell antibodies: 90% in adults with PA but also in 16% of NORMAL females over 60
25
Q

so in patients with low B12, what should you measure?

A
  • antibodies to parietal cells and IF
  • antibodies for coeliac
  • breath test ofr bacterial overgrowth
  • stool test for H. pylori and test for giardia
  • Shilling test
26
Q

what is part 1 of Shilling test?

A
  • give injections of B12 to saturate stores
  • then pt drinks radiolabelled B12
  • measure excretion of B12 in urine
  • normally expect it to come out in urine as stores are full
  • if none in urine, possibilities: not absorbing B12 (PA, small bowel disease), hasn’t corrected B12 def before test
27
Q

what is part 2 of the Shilling’s test?

A

repeat test but with addition of IF and measure excretion of B12 in urine

28
Q

what would be seen in these tests in someone with PA with autoantibodies to B12

A

P1: low, P2: normal

29
Q

what is the treatment of B12 def?

A
  • injections of B12 (3x a week for 2 weeks and thereafter every 3 month)
  • if neurological involvement, B12 injections alternate days until no further improvement

notes to flashcards year 2 - MCD (24 decks)

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