Macrocytic anemia

Question 1

Anemia with an MCV > 100um3…

Answer 1

Macrocytic anemia

Question 2

What are the 2 most common causes of macrocytic anemia?

Answer 2

Folate deficiency

Vitamin B12 deficiency

Question 3

What must be removed from serum methyltetrahydrofolate (THF) in order for it to participate in DNA synthesis?

Answer 3

Methyl group must be transferred to Vitamin B12

Question 4

Where is the methy group transferred to from methyltetrahydrofolate to allow THF to participate in DNA synthesis?

Answer 4

Vitamin B12

Question 5

Where does Vitamin B12 transfer the methyl group to produce methionine?

Answer 5

Homocysteine

Question 6

What leads to megaloblastic anemia?

Answer 6

Impaired division and enlargement of RBC precursors

Question 7

Hypersegmented neutrophils occur with macrocytic anemia. What causes there to be produced?

Answer 7

Impaired division of granulocytic precursors

Question 8

What are some causes of macrocytic anemia without megaloblastic change?

Answer 8

Alcoholism
Liver disease
Drugs (5-FU)

Question 9

Where does the absorption of folate occur?

Answer 9

Jejunum

Question 10

What are some common causes of folate deficiency?

Answer 10

Poor diet
Increased demand
Folate antagonists

Question 11

Macrocytic anemia can be caused by a poor diet. Who are the two most common groups of people who present with a folate deficiency due to poor diet?

Answer 11

Alcoholics

Elderly

Question 12

What are some causes of increased demand for folate, causing a folate deficiency?

Answer 12

Pregnancy
Cancer
Hemolytic anemia

Question 13

What is a common drug that is a folate antagonist causing a folate deficiency?

Answer 13

Methotrexate—inhibits dihydrofolate reductase

Question 14

What changes are seen with RBCs with folate deficiency?

Answer 14

Macrocytic RBCs

Question 15

What changes are seen with neutrophils with folate deficiency?

Answer 15

Hypersegmented neutrophils (> 5 lobes)

Question 16

With respect to folate levels and serum homocysteine, what are the laboratory values seen with a folate deficiency?

Answer 16

Serum folate—decreased

Homocystein—increased

Question 17

What is a normal finding seen with folate deficiency with helps differentiated it from a different cause macrocytic anemia?

Answer 17

Methylmalonic acid

Question 18

What is bound to vitamin B12 to allow it to be carried to through the stomach?

Answer 18

R-binder

Question 19

What cause the detachment of R-binder from vitamin B12?

Answer 19

Pancreatic proteases

Question 20

Where does the detachment of R-binder from vitamin B12 occur?

Answer 20

Duodenum

Question 21

What binds vitamin B12 in the small bowel allowing absorption of B12 by the ileum?

Answer 21

Intrinsic factor

Question 22

What cells produce intrinsic factor, which binds vitamin B12 to allow absorption in the ileum?

Answer 22

Gastric parietal cells

Question 23

What is the most common cause of vitamin B12 deficiency?

Answer 23

Pernicious anemia

Question 24

Autoimmune disorder involving destruction of parietal cells, which leads to intrinsic factor deficiency?

Answer 24

Pernicious anemia

Question 25

Besides pernicious anemia, what are some other causes of vitamin B12 deficiency?

Answer 25

Pancreatic insufficiency Damage to terminal ileum Dietary deficiency (RARE, except in vegans)

Question 26

What are the two most common causes of damage to the terminal ileum, which causes a vitamin B12 deficiency?

Answer 26

``` Crohn disease Diphyllobothrium latum (tapeworm) ```

Question 27

What are changes that occur to RBCs with vitamin B12 deficiency?

Answer 27

Macrocytic RBCs

Question 28

What changes occur to neutrophils with vitamin B12 deficiency?

Answer 28

Hypersegmented neutrophils

Question 29

Why is poor proprioception and vibratory sensation, along with spastic paresis seen with vitamin B12 deficiency?

Answer 29

Vitamin B12 is cofactor for the conversion of methylmalonic acid to succinyl CoA With Vitamin B12 deficient→ there is an increased level of methylmalonic acid impairing the spinal cord myelinization

Question 30

With respect to serum Vitamin B12, serum homocysteine, and Methylmalonic acid, what are the laboratory results seen with a vitamin B12 deficiency?

Answer 30

Serum Vitamin B12→ decreased Serum homocysteine→ Increased Methylmalonic acid→ increased

Question 31

What laboratory finding allows differentiation between a folate deficiency and a Vitamin B12 deficiency?

Answer 31

Methylmalonic acid levels Normal with folate deficiency Elevated with vitamin B12 deficiency