Vitamin B12 Deficiency Flashcards
1
Q
what is the term for compounds with biologic vitamin B12 activity?
A
cobalamin
2
Q
what is the function of cobalamin?
A
- nucleic acid metabolism
- methyl transfer
- myelin synthesis
3
Q
what are dietary sources of vitamin B12?
A
- meat (e.g. beef, pork, liver)
- poultry
- eggs
- fortified cereals
- milk
- seafood (e.g. clams, oysters, mackerel)
4
Q
what is the aetiology of vitamin B12 deficiency?
A
- inadequate intake (e.g. vegan)
- inadequate absorption (e.g. decreased acid secretion, SIBO)
- decreased utilisation
- medication (e.g. antacid, metformin)
5
Q
what is pernicious anaemia, and how is it different from general vitamin B12 deficiency?
A
- pernicious anaemia is a specific type of anaemia caused by vitamin B12 deficiency due to autoimmune metaplastic atrophic gastritis, leading to loss of IF
- it is often used synonymously with B12 deficiency but refers specifically to this autoimmune cause
6
Q
what are the symptoms of vitamin B12 deficiency?
A
- anaemia
- ? splenomegaly/hepatomegaly
- ? weight loss
- ? glossitis
- subacute combined degeneration
- paranoia (e.g. megaloblastic madness)
7
Q
what is subacute combined degeneration (SCD)?
A
- degenerative changes in the nervous system due to vitamin B12 deficiency
- affect mostly brain and spinal cord white matter
- decreased position and vibratory sensation in the extremities are accompanied by mild to moderate weakness and hyporeflexia
- in later stages, spasticity, hyperreflexia with absent achilles reflexes, extensor plantar responses, greater loss of position and vibratory sensation in the lower extremities, and ataxia develop, sometimes in a stocking-glove distribution
8
Q
what are the investigations for vitamin B12 deficiency?
A
- FBC (e.g. megaloblastic anaemia)
- vitamin B12 ↓
- folate
- serum methylmalonic acid (MMA) ↑
- homocysteine ↑
- ? serum gastrin
- ? anti-IF antibodies
9
Q
what is the management of vitamin B12 deficiency?
A
supplemental vitamin B12 (e.g. hydroxocabalamin)
