B12 and folate deficiency Flashcards
What is B12 required for?
DNA synthesis
The integrity of the nervous system
What is folic acid required for?
DNA synthesis
Homocysteine metabolism
Which cells are affected by a deficiency in folate and B12?
All rapidly dividing cells:
- bone marrow
- Epithelial surfaces of mouth and gut
- Gonads
- Embryos
What are the clinical features of folate and B12 deficiency?
Anemia - weak + tired Jaundice Sterility Glossitis and angular cheilosis Weight loss, change of bowel habit Sterility
What it is the size of the red blood cell in folate and B12 deficiency?
High MCV
Macrocytic - red cell size bigger than normal
megaloblastic
What are the causes of macrocytic anaemia?
Vitamin B12/folate deficiency Liver disease or alcohol Hypothyroid Drugs e.g. azathioprine Haematological disorders: Myelodysplasia, aplastic anaemia Reticulocytosis e.g. chronic haemolytic anaemia
What does megaloblastic mean?
Describes the morphological changes in red cells precursors in the bone marrow.
What are the peripheral changes in megaloblastic anaemia?
Anisocytosis
Large red cells
Hypersegmented neutrophils
Giant metamyelocytes
If someone had macrocytosis you would investigate:
B12
Folate
Thyroid function test
Liver function test
What are two causes of hypersegmented neutrophils?
B12 and folate deficiency
Where can you find dietary folate?
Fresh leafy vegetables
Destroyed by: overcookinh/canning/processing
Who is at risk of folate deficiency?
Ignorance
Poverty
Apathy
Elderly + alcoholics
When would you have increased demand in folate?
PHYSIOLOGICAL
Pregnancy
Adolescence
Premature babies
PATHOLOGICAL
Malignancy
Erythoderma
Haemolytic anaemias
How would you diagnose low folate levels?
FBC - look at the folate levels
What are the consquences of folate deficiency?
Megaloblastic + macrocytic anaemia
Neural tube defects in developing fetus (Spina bifida
Anencephaly - pregnant women told to take doses of folic acid)
Increased risk of thrombosis in association with variant enzymes involved in homocysteine metabolism
What is homocysteine associated with?
atherosclerosis
premature vascular disease
What are consequences of B12 deficiency?
Neurological problems
Optic atrophy
Dementia
Common history includes:
Paraesthesiae Muscle weakness Difficult walking Visual impairment Psychiatric disturbance
What are causes of B12 deficiency?
Poor absorption - across the duodemum (very slow), most of it is by binding to the intrinsic factor (made in parietal cells in the stomach), this binds to ileal receptors- this is much faster
Reduced doetary intake - vegans not vegetarians as animal produce is rich in b12.
Infections/infestations
What three things are essential for the absorption of B12?
Intact stomach
Intrinsic factor
Functioning small intestine
What can cause a decrease in absorption of intrinsic factor?
a) post gastrectomy
b) gastric atrophy
c) antibodies to intrinsic factor or parietal cells
What is pernicious anaemia?
The autoimmune condition associated with SEVERE LACK OF IF
What are the tests for pernicious anaemia?
Intrinsic factor antibodies
Parietal cell antibodies
What can be an alternative explanation to the lack of absorption of B12?
Diseases of small bowel (terminal ileum)
a) Crohns
b) Coeliac disease
c) surgical resection
Infections: H Pylori Giardia Fish tapeworm Bacterial overgrowth
Drugs:
- Metformin
- Omeprazole
What is the schilling’s test?
Drink radiolabelled B12
Measured excretion in the urine - if absorbed then the radioactivity will be in the urine but if there is no B12 in the urine then this will pass straight to the poo.
If the B12 levels are normal the patient can still be deficient in B12 how would you test for this?
Measure methylmalonyl acid
Measure homocysteine
Look for anti-intrinsic factor antibodies
