Microcytic Anemias (Part 2)

Question 1

Describe mechanism how chronic disease can lead to anemia

Answer 1

Liver produces hepcidin which sequesters iron in storage sites by 1) limiting transfer of iron from macros to erythroid precursors and 2) suppressing erythropoietin production. Available iron decreases and so does Hb. Therefore microcytic anemia results.

Question 2

Laboratory findings in anemia caused by chronic disease

Answer 2

Increased ferritin, decreased TIBC, decreased serum iron, decreased % saturation, increased free erythrocyte protoporphyrin

Question 3

Tx for anemia of chronic disease

Answer 3

1) treat underlying condition 2) administer EPO

Question 4

What is sideroblastic anemia?

Answer 4

Anemia due to defective protoporphyrin synthesis; Decreased protoporphyrin results in low Hb and therefore microcytic anemia

Question 5

Describe the major reactions in protoporphyrin and heme synthesis

Answer 5

Aminolevulinic acid synthetase (ALAS) converts succ-CoA to aminolevulinic acid (ALA) using Vit B6 (RLS). ALA dehydrogenase (ALAD) converts ALA to prophobilinogen. Further rxns convert porphobilinogen to protoporphyrin. Ferrochelatase attaches protoporphyrin to iron to make heme w/i the mitochondria.

Question 6

If protoporphyrin is deficient, what happens?

Answer 6

Iron transferred to erythroid precursors and enters mitochondria to form heme. Without protoporphyrin, iron remains trapped within the mitochondria. Mitochondria form ring around nucleus. Cells called sideroblasts.

Question 7

What is the frequent defect in congenital sideroblastic anemia?

Answer 7

Aminolevulinic acid synthetase (ALAS) defect

Question 8

What are 3 common causes of acquired sideroblastic anemia?

Answer 8

Alcohol - poisons mitochondria, Lead poisoning inhibits aminolevulinic acid dehydrogenase (ALAD), Vit B6 deficiency - B6 is required ALAS cofactor

Question 9

What is the typical scenario resulting in Vit B6 deficiency and sideroblastic anemia?

Answer 9

Isoniazid treatment for TB

Question 10

What are the typical lab findings for sideroblastic anemia?

Answer 10

Increased ferritin, decreased TIBC, increased serum iron, increased % saturation

Question 11

What condition shows similar presentation as sideroblastic anemia?

Answer 11

Hemochromatosis