haemoglobin 9: B12 & folate Flashcards
what are the major roles of vitamin B12?
DNA synthesis, integrity of nervous system
what are the major roles of folate?
DNA synthesis, homocystine (an essential AA) metabolism
which cells are affected by B12 & folate deficiency?
all rapidly dividing cells affected eg bone marrow, epithelial surfaces of mouth and gut, gonads, embryos
what are the clinical features of B12 & folate deficiency?
- anaemia
- jaundice
- glossitis & angular cheilosis
- weight loss
- change of bowel habit
- sterility
- B12 = loss of proprioception
what is the MCV of a B12 / folate deficient person?
high - macrocytic + megaloblastic
what is the difference between macrocytic & megaloblastic?
macrocytic: average RBC size is above normal range
megaloblastic: morphological change in RBC precursors within the bone marrow
what are some causes of macrocytic anaemia?
- B12/folate deficiency
- liver disease/alcohol
- hypothyroidism
- drugs eg azathioprine
- haematological disorders eg aplastic anaemia, reticulocytosis, myelodysplasia
what are the normal changes observed in red cell maturation?
from erythroblast -> reticulocyte: cytoplasm becomes more pink (increased haemoglobin production)
and nucleus becomes smaller -> nonexistent (only small amounts of remnant nucleic acids)
what is megaloblastic anaemia?
anaemia defined by asynchronous maturation of nucleus and cytoplasm in erythroid series
what tests would you do if someone had a macrocytic anaemia?
- B12 & folate
- thyroid function
- liver function
- reticulocyte count
what are some causes of decreased folate intake?
ignorance, poverty, apathy
which groups of people have increased folate demand?
- pregnant
- adolescent
- premature babies
- people with malignancy
- erythoderma
- haemolytic anaemias
what defects can folate defeciency cause in foetuses?
- spina bifida
- anencephaly
- increased homocysteine levels in newborns associated with atherosclerosis & premature vascular disease
what are some consequences of B12 deficiency?
neurological problems eg bilateral peripheral neuropathy, subacute degeneration of spinal cord, optic atrophy, dementia
what are some possible histories of patients with B12 deficiency?
- paraesthesiae
- muscle weakness
- difficulty walking
- visual impairment
- psychiatric disturbance
on neurological examination what is noticeable about B12 deficiency?
absence of central + peripheral reflexes
what are the causes of B12 deficiency?
- 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
how is B12 absorbed?
only absorbed when bound to intrinsic factor (made in parietal cells in stomach)
what could affect B12 absorption?
- 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)
what is pernicious anaemia?
autoimmune condition associated with sever lack of IF (peak age 60yo, may have family history)
how would you determine the cause of B12 deficiency?
- antibodies to parietal cells & IF
- antibodies for coeliac disease
- breath test for bacterial overgrowth
- stool for H pylori
- test for Giardia
what is the Shilling test?
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
what is the treatment for B12 deficiency?
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
