Macrocytic Anemias

Question 1

Define a megaloblastic anemia and list three general causes

Answer 1

a group of disorders characterized by defective nuclear maturation cause by impaired DNA synthesis

Caused by:

1. deficiency of V. B12
2. deficiency of folate
3. drugs that interfere with DNA metabolism

Question 2

What are the typical bone marrow changes in a megaloblastic anemia?

Answer 2

RBC line shows megaloblasts and asynchronous maturation

WBC line shows giants metas/bands and asynchronous development

PLT line abnormal

Question 3

What is asynchronous maturation and how will it appear on a smear?

Answer 3

Defective DNA synthesis causes nucleus to mature at a slower rate while cytoplasm grows at normal rate

the result is big cells with finer chromatin, cabot rings, hypersegs, H-J bodies

90% ineffective hematopoiesis

Question 4

What changes will be seen in the peripheral blood

Answer 4

RBC - oval macrocytes, teardrops, H-J bodies, cabot rings

WBC - giant forms, hypersegmented polys (> 5 lobes)

PLT - may see giant platlets

Question 5

What lab results are associated with ineffective HP

Answer 5

Erythroid hyperplasia BM -> pancytopenia PB

increased precursors in the BM with a decreased release into PB indicates ineffective HP

decreased retic cound
increased serum bilirubin, LDH (enzyme released via hemolysis), and serum iron, serum ferritin

Question 6

Where is vitamin B12 absorbed?

Answer 6

ileum

Question 7

What is intrinsic factor (IF) and where is it produced

Answer 7

It binds to B12 and allows it to be absorbed and it is produced by parietal cells of the stomach

Question 8

What is the storage organ for B12 and how long would those stores expect to last?

Answer 8

Liver for 4~5 years

Question 9

What clinical features do Vitamin B12 and folate deficencies share?

Answer 9

pallor, weakness, fatigue, SOB. beefy red sore tongue, lemon yellow skin

Question 10

Which megaloblastic anemia is unique to neurological problems

Answer 10

B12 deficiency - clumsiness, impairment of memory, psychiatric problems, pins and needles sensation in toes

Question 11

What is the most common cause of B12 deficiency

Answer 11

impaired absorption/pernicious anemia

Question 12

What is the defect in pernicious anemia that hinders b12 absorption

Answer 12

its an inherited autoimmune disorder where antibodies attach IF and gastric parietal cells. it is treated with intramuscular b12 injections. Run a serum b12 level to test

Question 13

Explain how D. latum or increased GI flora causes a b12 deficiency

Answer 13

they will compete for the b12 in the gut and thus decrease the amount being absorbed

Question 14

Where is folate absorbed and what is the extent of body stores

Answer 14

jejunum and 4-5 months storage

Question 15

What is the most common cause of a folate deficiency

Answer 15

poor diet

Question 16

What are four causes of a folate deficiency

Answer 16

poor diet
impared absorption
increased requirements (hemolytic anemia, neoplastic disease, growth, pregnancy)
drug related (birth control, anti-TB, dilantin, AZT)

Question 17

What rbc morphology would you expect to see with a nonmegaloblastic anemia?

Answer 17

aniso, oval macrocytes, tear drops, HJ bodies, cabot rings

hypersegmented polys and decreased retic count

the CBC shows a decrease in all numbers except MCV and mchc

Question 18

What are two causes of non-megaloblastic anemia?

Answer 18

liver disease/alcoholism and reticulocytosis

Question 19

Why are targets seen in the PB of someone with liver disease

Answer 19

an increase in cholestrol misplaces HGB and results in targets. spur cells and stomatocytes will be seen with a nonmegaloblastic amenia too

Question 20

what is transcobalamin II

Answer 20

protein that transports vitamin b12 to the tissues