B12 and Folate deficiency Flashcards
What are the functions of B12 and folate?
B12 and folate are essential co-factors in linked biochemical reaction regulation
They have a role in DNA synthesis, nuclear maturation, DNA modification and gene activity
B12 also plays a role in lipid synthesis and myelin production
What reaction do B12 and folate play a role in in DNA synthesis?
Uracil -> Thymine
What reaction so B12 and folate play a role in, in gene expression modification?
Homocysteine -> Methionine
How is B12 absorbed?
Haptocorin is found in the saliva and binds to B12
This prevents the destruction of B12 in the stomach
Gastric parietal cells in the stomach release intrinsic factor
This travels with the B12-HC into the small bowel
Here, haptocorin dissociates from the B12 and intrinsic factor binds
This allows its absorption into the ileum via cubam receptors
How is folate absorbed?
Dietary folate is converted into monoglutamate for absorption in the jejunum
What are the most common sources of vitamin B12?
Meat
Eggs
What are some causes of vitamin B12 deficiency? (9)
- Dietary insufficiency
- Pernicious anaemia
- Atrophic gastritis
- PPI usage
- Gastrectomy
- Chronic pancreatitis
- Bacterial overgrowth
- Coeliac disease
- Crohn’s disease
What is pernicious anaemia?
An autoimmune condition resulting in the destruction of gastric parietal cells, therefore reducing levels of intrinsic factor, leading to malabsorption and deficiency
What are conditions are associated with pernicious anaemia?
Atrophic gastritis
History of other autoimmune conditions
What are some causes of folate deficiency?
- Inadequate intake
- Malabsorption
- Excess utilisation
- Drugs (e.g. methotrexate)
What are the main dietary sources of folate?
- Liver
- Leafy vegetables
- Fortified cereals
What non-diet based factor can lead to inadequate folate consumption?
Alcohol excess
What are some causes of malabsorption leading to folate deficiency?
Coeliac diasease
Crohns disease
What are some conditions that can lead to excess folate utilisation?
- Haemolysis
- Exfoliating dermatitis
- Pregnancy
- Malignancy
What are some drugs that can lead to folate deficiency?
- Anti-convulsants
- Methotrexate
What are some clinical features common to both B12 and folate deficiency? (9)
- Symptoms of anaemia
- Weight loss
- Diarrhoea
- Infertility
- Sore, beefy tongue
- Jaundice
- Developmental problems
- Pica (Dietary cravings for abnormal things such as dirt or soil)
- Hair loss
Why can B12 deficiency cause neurological dysfunction?
Due to its role in myelination of nerve cells
What are some neurological dysfunctions that can occur in B12 deficiency?
- Dorsal/Lateral column abnormalities
- Neuropathy
- Dementia
- Psychiatric manifestations
What are some tests used in the diagnosis of B12 and folate deficiency?
- Blood film
- Hb concentration
- Assay B12 and folate levels
- Autoantibodies (Pernicious anaemia)
- Schillings test (Now not routine)
- Bone marrow examination (Not usually required)
- Trial of therapy
What will be shown on blood film in B12 and folate deficiency?
- Pancytopenia (All cells low) in some patients
- Macrovalocytes
- Hypersegmented neutrophils (Normally 3-5 nuclear segments)
What are some things that can cause physiological low B12 levels?
Pregnancy
Oral contraceptive usage
What antibodies are found in pernicious anaemia?
- Anti-gastric-parietal cell antibodies (Sensitive, not specific)
- Anti-intrinsic factor antibodies (Specific, not sensitive)
What are the main management strategies used in B12 and folate deficiency?
- Treatment of the cause
- Dietary changes
- Oral supplementation (e.g. folic acid 5mg OD)
- Transfusion if life-threatening
What treatment is given in pernicious anaemia to prevent B12 deficiency?
Life-long vitamin B12 deficiency
