MACROCYTIC ANAEMIA Flashcards
What is the normal range for mean cell volume?
80-95 fl
What type of macrocytic anaemia does folate or B12 deficiency cause?
Megaloblastic anaemia (right shift)
What processes are affected by folate or B12 deficiency?
DNA synthesis
What is the daily requirement of vitamin B12?
1 microgram
Where is vitamin B12 absorbed?
Ileum
What must be present for vitamin B12 to be absorbed?
Intrinsic factor
Where is intrinsic factor excreted?
Parietal cells of the stomach.
What is the most common cause of vitamin B12 deficiency in the UK?
Pernicious anaemia
What is the underlying mechanism of pernicious anaemia?
Autoimmune gastritis where autoantibodies attack the parietal cells leading to a reduction in intrinsic factor.
Is pernicious anaemia more common in males or females?
Females
What is the peak age of onset for pernicious anaemia?
60
What diseases are associated with pernicious anaemia?
Vitiligo - patchy whiteness of the skin Myxoedema Hashimoto's disease Addison's disease Hypoparathyroidism
What is the daily requirement of folate?
100-200 micrograms
Where is folate absorbed in the intestine?
Upper small intestine
How long do body stores of folate usually last for?
4 months
What disease is especially associated with folate deficiency?
Coeliac disease
What are the clinical features of megaloblastic anaemia caused by a vitaman B12 or folate deficiency?
Pallor
Jaundice
Gradual onset
May present with signs of congestive heart failure
What does the blood film of someone with anaemia related to vitamin B12 or folate deficiency look like?
Oval macrocytes
Hypersegmented neutrophil neuclei
Low white cell or platelet count
What are the characteristics bone marrow features of megaloblastic anaemia?
Megaloblastic erythroblasts
Giant metamyelocytes
Other than low Hb, what might a blood test of someone with megaloblastic anaemia show?
Raised unconjugated bilirubin Raised serum lactic dehydrogenase Low B12 Low folate Raised serum homocysteine Parietal cell antibodies Intrinsic factor antibodies
Why is jaundice associated with megaloblastic anaemia?
Increased destruction of the red cell precursors in the marrow
Other than anaemia, what other effects are there from a vitamin B12 or folate deficiency?
Neuropathy Neural tube defects Gonadal dysfunction Epithelial changes - such as glossitis Cardiovascular disease
What is the most common cause of raised MCV of red blood cells (macrocytosis) in the UK?
Alcohol - even quite small amounts and not necessarily associated with liver disease
What are the causes of raised MCV of red blood cells?
Megaloblastic anaemia (B12 and folate) Alcohol Pregnancy and neonatal period Myelodysplasia Aplastic anaemia Changes in plasma protein (eg paraproteins associated with myeloma) Drugs - hydroxyurea and azathioprine Benign familial macrocytosis Hypothyroidism
Other than blood tests, what investigations would you do with someone who presented with megaloblastic anaemia?
Bone marrow examination
Radioactive vitamin B12 absorption study - with and without intrinsic factor
Endoscopy - to confirm atrophic gastritis or exclude gastric carcinoma
What are the causes of megaloblastic anaemia?
Diet Pernicious anaemia Congenital intrinsic factor deficiency Gastrectomy Atrophic gastritis Stagnant loop Congenital selective malabsorption Ileal resection Crohn's Coeliac disease Jejunal resection Drugs - anticonvulsants, sulphasalazine
What is the medical treatment of vitamin B12 deficiency?
Initial treatment is injections of hydroxycobalamin 1 mg every 3-4 days, followed by 4 injections a year for life.
What is the medical treatment of folate deficiency?
Folic acid 5 mg daily for 4 months
Those with severe haemolytic anaemia should continue to have this dose once a week.
What must you do before starting someone on treatment for folate deficiency?
Check vitmamin B12 levels as treatment may correct anaemia but allow neurological disease to develop.
