Vitamin B12 & Folate deficiency Flashcards
Define B12 deficiency.
Vitamin B12 deficiency is a common condition that can manifest with neurological, psychiatric, and haematological disorders.
What is the aetiology of B12 deficiency?
Decreased dietary intake - vegans, strict vegetarians
Diminished gastric breakdown of vitamin B12 from food - atrophic gastritis, pernicious anaemia
Malabsorption from the gastrointestinal tract - Coeliac, Crohn’s, bacterial overgrowth syndromes
What are the cut-offs for B12 deficiency?
- < 148 pmols/L (< 200 picograms/mL) indicates probable deficiency;
- 148 to 258 pmols/L (201-350 picograms/mL) indicates possible deficiency;
- > 258 pmols/L (> 350 picograms/mL) indicates that deficiency is unlikely
How common is B12 deficiency?
6% < 60yrs affected
20% > 60yrs affected
What are the sources of B12?
NB: B12 is an essential vitamin only obtained from diet or supplementation
Animal and dairy = meat, poultry, milk, eggs
Supplementation
What are some groups at-risk of B12 deficiency?
- Vegans
- History of gastric or intestinal surgery
- History of atrophic gastritis
- Pernicious anaemia, in which autoimmune destruction of the parietal cells (which produce intrinsic factor) leads to reduced vitamin B12 absorption from the gastrointestinal tract
- Gastric malabsorption.
Describe the process by which B12 enters the blood stream.
B12 ingested and released from food by peptic acid
B12 binds IF and this complex travels for endocytosis by the terminal ileum
B12 is bound by transcobalamin and is released into the serum for utilisation
Why does B12 deficiency afffect neural function?
Because it is important in conversion of homocysteine to methionine which is needed for S-adenosylmethionine production (important in neural function)
What are the clinical features of B12 deficiency?
- macrocytic anaemia
- sore tongue and mouth
- neurological symptoms - the dorsal column is usually affected first (joint position, vibration) prior to distal paraesthesia
- neuropsychiatric symptoms: e.g. mood disturbances
Other:
* glossitis
* angular cheilitis
* pallor
* Positive Romberg’s
* decreased vibration sense
* ataxia
What is the management of B12 deficiency?
No severe symptoms:
* IM hydroxycobalamin - 1mg x3/week for 2 weeks then once every 3 months.
NB: treat B12 deficiency before any folic acid to avoid precipitating subacute combined degeneration of the cord
If symptomatic, severe deficiency:
* Daily IM cyanocobalamin 1-2 weeks
What are the complications and prognosis of B12 deficiency?
Untreated pernicious anaemia -> gastric cancer
Progressive anaemia, leukopenia, thrombocytopenia
Progressive neurological damage - many cases are irreversible, early diagnosis in asymptomatic stage is crucial
Dementia, peripheral neuropathy, depression
Define folate deficiency.
B9 deficiency which most commonly manifests with megalobalstic anaemia WITHOUT neuropathy.
What are some sources of folate?
Green vegetables
Legumes
Some fruits
What is the aetiology of folate deficiency?
Inadequate intake - unfortified cereals, excess cooking destroying folate, poor intake, special phenylketonuria diet, goat’s milk (completely deficient in folate)
Intestinal malabsorption - tropical sprue, coeliac
Increased demand - pregnancy, lactation
Increased loss - chronic dialysis, chronic haemolytic disease, exfoliative dermatitis
What are the functions of folate in the body?
Essential for purine and thymidylate synthesis
DNA synthesis and repair
Normal development of CNS
