RBC Disorders 3

Question 1

What is the most common cause of macrocytic/megaloblastic anemia?

Answer 1

folate deficiency

Question 2

Where in GI tract is folate absorbed?

Answer 2

in the jejunum

Question 3

What are the causes of folate definiency?

Answer 3

(1) poor diet (alcoholics and elderly)
(2) increased demand (pregnancy, cancer, hemolytic anemia)
(3) folate antagonists (e.g., methotrexate, which inhibits dihydrofolate reductase)

Question 4

What are the clinical and lab findings of folate deficiency? (5)

Answer 4

(1) macrocytic RBCs and hypersegmented neutrophils
(2) glossitis
(3) dec. serum folate
(4) inc. serum homocysteine
(5) normal methylmalonic acid

Question 5

What is a downstream risk of increased serum homocysteine?

Answer 5

It increases the risk for thrombosis

Question 6

For what biosynthetic process are folate and B12 needed?

Answer 6

for the synthesis of DNA precursors

Question 7

What cellular changes are seen with folate and B12 deficiency?

Answer 7

(1) impaired division and enlargement of RBC precursors leads to megaloblastic anemia
(2) impaired division of granulocytic precursors leads to hypersegmented neutrophils
(3) megaloblastic change is also seen in rapidly dividing (e.g., intestinal) epithelial cells

Question 8

Why are cells increased in size in megaloblastic anemia? (in a folate or B12 deficiency, for example)

Answer 8

The lack of folate and B12 inhibits DNA synthesis. When DNA synthesis is impaired, the cell cycle cannot progress from the G2 to mitosis. This leads to continued cell growth without division, which presents as macrocytosis