Microcytic Anemias

Question 1

What is the most common type of anemia?

Answer 1

Iron-deficiency anemia

Question 2

What are microcytic anemias (MCV <80) usually due to?

Answer 2

Lack of hemoglobin production

• Iron deficiency
• Defect in heme group / protoporphyrin ring synthesis (Sideroblastic anemia)
• Defect in the heme protein itself (Thalassemias)
• Anemia of chronic disease (Can also be normocytic)

Question 3

What are normocytic anemias (MCV 80 - 99) usually due to?

Answer 3

• Anemia of chronic disease
• Paroxysmal nocturnal hemoglobinuria
• G6PD Deficiency
• Hereditary spherocytosis

Question 4

What are macrocytic anemias (MCV >100) usually due to?

Answer 4

• B₁₂ deficiency (Malnutrition, chronic gastritis, pernicious anemia)
• Folate deficiency (Malnutrition, alcoholism, chemotherapy)

Question 5

What is a likely cause of iron-deficiency anemia in an older man?

Answer 5

Colon cancer and colorectal bleeding (Until proven otherwise)

Question 6

What labs are seen in iron-deficiency anemia?

Answer 6

Low ferritin (Iron-storage protein)

High transferrin / total iron-binding capacity

Hypochromic (Pale RBCs)

Microcytic

Question 7

What anemia is associated with Plummer-Vinson Syndrome?

Answer 7

Iron-deficiency anemia (Along with esophageal webs and dysphagia)

Question 8

What do hypochromic RBCs look like?

Answer 8

Question 9

What is sideroblastic anemia?

Answer 9

A microcytic anemia resulting from an abnormality in heme production in the porphyrin pathway.

Question 10

What is the most common cause of sideroblastic anemia?

What are some other causes?

Answer 10

ALA synthetase deficiency

• Lead poisoning*
• Administration of certain medications (E.g. isoniazid)*

Question 11

What happens with Fe²⁺ and heme in the mitochondria?

What happens during sideroblastic anemia?

Answer 11

Fe²⁺ and heme are joined in the mitochondria.

In sideroblastic anemia, we have a heme deficiency, and so Fe²⁺ builds up in the mitochondria.

Question 12

What enzymes in heme synthesis are inhibited in lead poisoning?

Answer 12

ALA dehydratase

Ferrochetalase

Question 13

How does isoniazid (TB antibiotic) cause sideroblastic anemia?

Answer 13

Isoniazid inhibits vitamin B₆ (which is a cofactor in ALA synthase activity)

Question 14

What can Prussian blue be used to stain in the cell?

Answer 14

Iron (Especially in sideroblastic anemia)

Question 15

What are the lab results for sideroblastic anemia?

Answer 15

Increased iron

Increased ferritin

Decreased total iron-binding capacity / transferrin

Question 16

What are the thalassemias?

Answer 16

Microcytic anemias caused by an abnormality in hemoglobin synthesis (The peptide itself) due to a deletion in the gene.

Question 17

How many alpha and beta genes are there for thalassemia?

Answer 17

4 alpha

2 beta

Question 18

What is the impact of different amounts of alpha deletions in thalassemia?

Answer 18

1 deletion - Asymptomatic

2 deletions - mild anemia

3 deletions - severe anemia

4 deletions - hydrops fetalis

Question 19

Is there a difference in mild (2 deletions) alpha-thalassemias by race?

Answer 19

Asian –> CIS deletion (Both on same chromosome)

African –> TRANS deletion (On different chromosomes)

Question 20

What is the impact of a different number of mutations in beta-thalassemia?

Answer 20

1 deletion - beta-thalassemia minor (Mostly asymptomatic)

2 deletions - beta-thalassemia major (Chipmunk facies and crew cut skull x-ray)

Question 21

Why does beta-thalassemia major result in chipmunk facies and a crew cut appearance on X-ray?

Answer 21

Extramedullary hematopoiesis (The body is trying to compensate for decreased erythropoeisis by stimulating RBC production in other bones; e.g. the skull and face)

Question 22

What type of hemoglobin is elevated in beta-thalassemia major?

Answer 22

Hemoglobin A₂

Question 23

What is anemia of chronic disease?

Answer 23

Anemia due to an underlying, chronic inflammation

Question 24

What acute inflammatory product is involved in anemia of chronic disease? What is the mechanism of action?

Answer 24

Hepcidin; inflammation triggers hepcidin to decrease gut iron absorption and increase iron storage by ferritin

Question 25

What labs are associated with anemia of chronic disease?

Answer 25

Decreased iron

Increased ferritin

Decreased total iron-binding capacity / transferrin

Question 26

What are three non-infectious diseases that are commonly associated with anemia of chronic disease?

Answer 26

Kidney disease

Autoimmunity

Rheumatologic diseases