Vitamin B12 Deficiency Flashcards
B12 Physiology:
What is another name for B12?
What does B12 do? - 2
How does the stomach aid digestion of B12?
What is released that aids digestion of B12?
Where is absorption taking place?
Cobalamin
(1) Plays key role in DNA synthesis and hence in cells with rapid turnover (e.g. haematopoiesis)
(2) Myelin formation
Release of B12 from food
Gastric parietal cells release intrinsic factor (IF) which binds to B12
Terminal ileum as a B12-IF complex
Causes:
Impaired gastric function:
- Autoimmune destruction of gastric parietal cells could cause this. What is this called?
- What stomach surgery will hinder the gastric function?
- Zollinger-Ellison syndrome is a cause. What is it?
Pernicious anaemia
Gastroectomy
A rare condition in which one or more tumours form in your pancreas or the upper part of your small intestine (duodenum). These tumours, called gastrinomas, secrete large amounts of the hormone gastrin, which causes your stomach to produce too much acid.
Causes:
Impaired intestinal absorption - think of some causes? - 2
Decreased intake:
- Why are vegans susceptible to this?
- Malnutrition is another cause.
Drugs:
- Why do PPI’s and H2 blockers cause this?
- What diabetics medication reduces B12 levels in the body?
- Why does alcohol cause this?
Crohn’s Disease
Ileal resection
B12 is only found in animals products - Meat and dairy products
Caused by reduced gastric acidity, which prevents the release of vitamin B12 from food.
Metformin
It decreases B12 absorption
Presentation - Megaloblastic anaemia:
Angular cheilosis - what is it?
What happens to their tongue?
Why may their skin have a lemon tinge?
Also called stomatitis
Ulceration at the side of the mouth
Also found in iron deficiency anaemia
Red, raw, big beefy tongue
Dye to the combo of pallor and mild jaundice (due to haemolysis)
Presentation - Neurological manifestations:
Why do they get neurological symptoms?
What UMN symptoms and signs would they have?
What LMN symptoms and signs would they have?
Due to its role in myelin production
The neurological problems caused by vitamin B12 deficiency later in life are due to the damage caused to the myelin sheath.
UMN:
- Impaired proprioception
- Unsteadiness
- Spastic paraparesis
- Dysaesthesia
- Extensor planters
LMN:
- Absent knee and ankle reflex
May also cause psychosis and impaired cognition
Investigations:
FBC - what do you expect MCV to be?
What should be tested to look for serum B12 levels?
High MCV
Serum cobalamin
Investigations - Pernicious anaemia:
Thinking about the mechanism of pernicious anaemia, what blood tests can you look for?
Parietal cell antibodies
IF antibodies
Management:
Rx underlying cause
Hydroxocobalamin - 1st line:
- Route
- How often are they taken?
IM
3 monthly
