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haem > haemoglobin 9: B12 & folate > Flashcards

haemoglobin 9: B12 & folate Flashcards

1
Q

what are the major roles of vitamin B12?

A

DNA synthesis, integrity of nervous system

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2
Q

what are the major roles of folate?

A

DNA synthesis, homocystine (an essential AA) metabolism

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3
Q

which cells are affected by B12 & folate deficiency?

A

all rapidly dividing cells affected eg bone marrow, epithelial surfaces of mouth and gut, gonads, embryos

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4
Q

what are the clinical features of B12 & folate deficiency?

A
  • anaemia
  • jaundice
  • glossitis & angular cheilosis
  • weight loss
  • change of bowel habit
  • sterility
  • B12 = loss of proprioception
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5
Q

what is the MCV of a B12 / folate deficient person?

A

high - macrocytic + megaloblastic

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6
Q

what is the difference between macrocytic & megaloblastic?

A

macrocytic: average RBC size is above normal range
megaloblastic: morphological change in RBC precursors within the bone marrow

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7
Q

what are some causes of macrocytic anaemia?

A
  • B12/folate deficiency
  • liver disease/alcohol
  • hypothyroidism
  • drugs eg azathioprine
  • haematological disorders eg aplastic anaemia, reticulocytosis, myelodysplasia
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8
Q

what are the normal changes observed in red cell maturation?

A

from erythroblast -> reticulocyte: cytoplasm becomes more pink (increased haemoglobin production)
and nucleus becomes smaller -> nonexistent (only small amounts of remnant nucleic acids)

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9
Q

what is megaloblastic anaemia?

A

anaemia defined by asynchronous maturation of nucleus and cytoplasm in erythroid series

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10
Q

what tests would you do if someone had a macrocytic anaemia?

A
  • B12 & folate
  • thyroid function
  • liver function
  • reticulocyte count
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11
Q

what are some causes of decreased folate intake?

A

ignorance, poverty, apathy

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12
Q

which groups of people have increased folate demand?

A
  • pregnant
  • adolescent
  • premature babies
  • people with malignancy
  • erythoderma
  • haemolytic anaemias
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13
Q

what defects can folate defeciency cause in foetuses?

A
  • spina bifida
  • anencephaly
  • increased homocysteine levels in newborns associated with atherosclerosis & premature vascular disease
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14
Q

what are some consequences of B12 deficiency?

A

neurological problems eg bilateral peripheral neuropathy, subacute degeneration of spinal cord, optic atrophy, dementia

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15
Q

what are some possible histories of patients with B12 deficiency?

A
  • paraesthesiae
  • muscle weakness
  • difficulty walking
  • visual impairment
  • psychiatric disturbance
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16
Q

on neurological examination what is noticeable about B12 deficiency?

A

absence of central + peripheral reflexes

17
Q

what are the causes of B12 deficiency?

A
  • reduced dietary intake (not as common as stores are large and last 3-4 years, found in animal produce -> vegans are at risk),
  • infections/infestations (tropical sprue, fishtapeworm etc)
  • reduced absorption
18
Q

how is B12 absorbed?

A

only absorbed when bound to intrinsic factor (made in parietal cells in stomach)

19
Q

what could affect B12 absorption?

A
  • reduced IF (post gastrectomy, gastric atrophy, antibodies to IF or parietal cells)
  • diseases of terminal ileum (crohns, coeliac, surgical resection)
  • infection (H pylori, bacterial overgrowth, giardia)
  • drugs (metformin, PPIs eg omeprazole, oral contraceptive)
20
Q

what is pernicious anaemia?

A

autoimmune condition associated with sever lack of IF (peak age 60yo, may have family history)

21
Q

how would you determine the cause of B12 deficiency?

A
  1. antibodies to parietal cells & IF
  2. antibodies for coeliac disease
  3. breath test for bacterial overgrowth
  4. stool for H pylori
  5. test for Giardia
22
Q

what is the Shilling test?

A

drink with radiolabelled B12 given and radioactivity of urine measured - radioactivity in urine means B12 has been absorbed, separate isotope given with addition of IF and again measure excretion of B12 in urine

23
Q

what is the treatment for B12 deficiency?

A

treat underlying cause, IM injections of B12 3xweek for 2 weeks then every 3 months, if neurological involvement then alternate days for 3 weeks then every 2 months

haem (21 decks)

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