Macrocytic anemias Flashcards
(23 cards)
What cell makes platelets?
Megakaryocyte
What does folate come into the body as?
THF (tetrahydrofolate)
What happens to THF as soon as its uptaken?
Methylated
What takes THF’s methyl group?
B12
- This then allows folate to engage in DNA precursor synthesis
What does B12 pass its methyl group to?
Homocysteine
- It then becomes Methionine
What are two things specific to megaloblastic anemia?
- Hypersegmented neutrophils
- Megaloblastic changes in rapidly-dividing epithelial cells (e.g. intestine)
How many lobes makes a neutrophil hypersegmented?
More than 5
3-5 is normal
What chemotherapy drug may induce a macrocytic anemia?
5-FU (non-megaloblastic)
Where is folate absorbed?
Jejunum
How long does it take for a folate deficiency to develop?
Within months
- Body stores are minimal
What are causes of folate deficiency?
- Poor diet (alcoholics and elderly)
- Increased demand (pregnancy, cancer, hemolytic anemia)
- Folate antagonists (e.g. methotrexate)
What are the homocysteine levels like in folate deficiency?
Increased serum homocysteine
What substance binds to B12 and is produced by salivary glands?
R binder
What cleaves B12 and R binder?
Proteases produced by the pancreas
What substance binds to B12?
Intrinsic factor
- Produced by parietal cells in body of stomach
Where is B12 absorbed?
Ileum
What is more common B12 or folate deficiency and why?
B12 is less common
- Takes years to develop B12 deficiency as there are large hepatic stores of B12
What is the most common cause of B12 deficiency?
Pernicious anemia
- Autoimmune destruction of parietal cells (body of stomach) leads to intrinsic factor deficiency
What are the 3 Ps associated with parietal cells?
- Pink
- Proton pump (produces HCl)
- Damage to them causes pernicious anemia
What are the other causes of B12 deficiency?
- Pancreatic insufficiency
- Damage to terminal ileum (Crohns or Diphyllobothrium latum)
- Dietary deficiency (vegans)
What is specific to B12 deficiency?
Subacute combined degeneration of spinal cord
- Degeneration of the dorsal columns and the lateral columns of the spinal cord due to demyelination
- Sensory deficits, paresthesia, weakness, ataxia, and gait disturbance
What are the levels of homocysteine in both B12 and folate deficiency?
Increased serum homocysteine in both
What does B12 cause MMA to turn into?
Succinyl coA
