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USMLE Hematology Leukemmia and Lymphoma > Macrocytic anemias > Flashcards

Macrocytic anemias Flashcards

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USMLE® Step 1 flashcards
1
Q

What cell makes platelets?

A

Megakaryocyte

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2
Q

What does folate come into the body as?

A

THF (tetrahydrofolate)

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3
Q

What happens to THF as soon as its uptaken?

A

Methylated

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4
Q

What takes THF’s methyl group?

A

B12

- This then allows folate to engage in DNA precursor synthesis

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5
Q

What does B12 pass its methyl group to?

A

Homocysteine

- It then becomes Methionine

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6
Q

What are two things specific to megaloblastic anemia?

A
  • Hypersegmented neutrophils

- Megaloblastic changes in rapidly-dividing epithelial cells (e.g. intestine)

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7
Q

How many lobes makes a neutrophil hypersegmented?

A

More than 5

3-5 is normal

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8
Q

What chemotherapy drug may induce a macrocytic anemia?

A

5-FU (non-megaloblastic)

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9
Q

Where is folate absorbed?

A

Jejunum

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10
Q

How long does it take for a folate deficiency to develop?

A

Within months

- Body stores are minimal

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11
Q

What are causes of folate deficiency?

A
  • Poor diet (alcoholics and elderly)
  • Increased demand (pregnancy, cancer, hemolytic anemia)
  • Folate antagonists (e.g. methotrexate)
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12
Q

What are the homocysteine levels like in folate deficiency?

A

Increased serum homocysteine

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13
Q

What substance binds to B12 and is produced by salivary glands?

A

R binder

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14
Q

What cleaves B12 and R binder?

A

Proteases produced by the pancreas

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15
Q

What substance binds to B12?

A

Intrinsic factor

- Produced by parietal cells in body of stomach

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16
Q

Where is B12 absorbed?

A

Ileum

17
Q

What is more common B12 or folate deficiency and why?

A

B12 is less common

- Takes years to develop B12 deficiency as there are large hepatic stores of B12

18
Q

What is the most common cause of B12 deficiency?

A

Pernicious anemia

- Autoimmune destruction of parietal cells (body of stomach) leads to intrinsic factor deficiency

19
Q

What are the 3 Ps associated with parietal cells?

A
  • Pink
  • Proton pump (produces HCl)
  • Damage to them causes pernicious anemia
20
Q

What are the other causes of B12 deficiency?

A
  • Pancreatic insufficiency
  • Damage to terminal ileum (Crohns or Diphyllobothrium latum)
  • Dietary deficiency (vegans)
21
Q

What is specific to B12 deficiency?

A

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
22
Q

What are the levels of homocysteine in both B12 and folate deficiency?

A

Increased serum homocysteine in both

23
Q

What does B12 cause MMA to turn into?

A

Succinyl coA

USMLE Hematology Leukemmia and Lymphoma (14 decks)

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