2: Macrocytic anaemia and macrocytosis Flashcards
What MCV defines macrocytosis
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What are the 3 types of macrocytosis
- Megaloblastic
- Non-Megaloblastic
- Other
What are 3 causes of megaloblastic macrocytosis
Vitamin B12 Deficiency
Folate Deficiency
Anti-Folate Medications
How long do vitamin B12 stores usually last
3-5 years
What condition can lead to vitamin B12 deficiency
Pernicious anaemia
How long do folate stores last
3-months
What are 4 anti-folate medications
Trimethoprim
Phenytoin
Methotrexate
Hydroxyurea
What are non-megaloblastic causes of macrocytic anaemia
Hypothyroidism Pregnancy Macrocytosis Reticulocytosis Liver Disease
What are 4 other causes of microcytic anaemia
- MDS
- MPD
- Myeloma
- Aplastic anaemia
Explain pathophysiology of macrocytic anaemia
- Macrocytosis is due to a defect in DNA production
- It is where cells do not have the correct number of DNA copies.
- In response cells keep increasing in size
- If too large cells will undergo intra-medullary haemolysis causing anaemia
- To compensate bone marrow increases cell production resulting in megalocytosis
- Megalocytosis also happens to other cells causing hyper-segmented neutrophil appearance
What is first-line in anaemia
FBC
What is looked at after FBC
Vitamin B12 and Folate
What is then looked at
Peripheral blood smear
What will be seen on peripheral blood smear
Hyper-segmented neutrophils if megaloblastic
When is a bone marrow biopsy indicated
If cause not identified by previous tests
How long does the body store folate for
3-months
Where is folate absorbed
Jejunum
What can lead to folate deficiency
- Alcoholism
- Malnutrition
- Increased demand: pregnancy, coeliac disease
- Anti-Folate medications
How is folate deficiency managed
Folic acid supplementation
What should folic acid always be given with and why
B12.
If Folic acid is given in B12 deficiency it can precipitate subacute combined degeneration of the spinal cord
How much folic acid is given routinely in pregnancy
400mcg
What should always be given before folate
Vitamin B12
B4 Folate
What is the role of vitamin B12
Vitamin B12 helps synthesise thymidine and therefore is required for RBC and DNA synthesis
How long do vitamin B12 stores last
3-5 Years
Where is vitamin B12 absorbed
Terminal Ileum
What can cause vitamin B12 deficiency
- Poor Intake
- Malabsorption
What can lead to poor intake of vitamin B12
B12 is found in meat and fish - therefore vegans can be deficient
What malabsorption conditions can lead to vitamin B12 deficiency
- Pernicious anaemia
- Gastrectomy
Conditions affecting terminal ileum:
- Crohn’s
- Ileal resection
- Topical sprue
- Bacterial overgrowth
What dermatological feature has been described in vitamin B12 deficiency
Lemon-tinge to skin
Why is a lemon tinge to skin described in vitamin B12 deficiency
Jaundice and anaemia
What are neurological complications of vitamin B12 deficiency
- Neuropsychiatric: Depression
- Neurological: Sub-acute combined degeneration spinal cord, peripheral neuropathy
How does subacute combined degeneration spinal cord present
Mixed UMN and LMN. Often with classic triad of:
- Upgoing plantar
- Absent knee jerk
- Absent ankle jerk
Explain pernicious anaemia
Autoimmune disorder causing atrophic gastritis and preventing parietal cells releasing IF which is required for absorption vitamin B12 in terminal ileum
What are RF for pernicious anaemia
- Over 40
- Other autoimmune diseases
- Blood-group A
What cancer does pernicious anaemia increase risk of
Gastric carcinoma
Explain FBC in pernicious anaemia
Macrocytic anaemia
Explain vitamin B12 in pernicious anaemia
Low
Explain parietal cell antibodies in pernicious anaemia
Parietal cell antibodies (90%)
How is pernicious anaemia managed
IM Vitamin B12
What is vitamin B12 called
Hydoxocobalamin
