Thalassemia

Question 1

An anemia due to the decreased synthesis of the globin chains of hemoglobin…

Answer 1

Thalassemia

Question 2

Carriers of inherited mutation seen in thalassemias are protected against what?

Answer 2

Plasmodium falciparum malaria

Question 3

What are the 3 normal types of hemoglobin?

Answer 3

HbF (a2, g2)
HbA (a2, B2)
HbA2 (a2, d2)

Question 4

a-Thalassemias are usually caused by what type of gene defect?

Answer 4

Gene deletion

Question 5

How many alpha genes are present on chromosome 16?

Answer 5

4

Question 6

If one alpha gene is deleted from chromosome 16, what symptoms is the patient most likely to experience?

Answer 6

Non

Question 7

If two alpha genes are deleted from chromosome 16, what is the patient most likely to experience?

Answer 7

Mild anemia with an increased RBC count

Question 8

What type of alpha deletion from chromosome 16 is associated with an increased risk of severe thalassemia in offspring?

Answer 8

Cis deletion—both deletions occur on the same chromosome

Question 9

What ethic group has an increased incidence of Cis deletions of the alpha gene on chromosome 16?

Answer 9

Asians

Question 10

What are the two deletions that cause occur when two alpha genes are deleted from chromosome 16?

Answer 10

Cis or Trans

Question 11

What occurs in patients who have three alpha gene deletions on chromosome 16?

Answer 11

Severe anemia

Question 12

When a patient presents with three alpha gene deletions on chromosome 16, what do the B chains form, which cause damage to the RBCs?

Answer 12

Tetramers (HbH)

Question 13

When a patient presents with three alpha gene deletions on chromosome 16, what is seen on electrophoresis?

Answer 13

HbH—Beta tetramers

Question 14

What is the most likely prognosis of a patient who has four alpha gene deletions on chromosome 16?

Answer 14

Lethal in utero—hydrops fetalis

Question 15

When four alpha gene deletions on chromosome 16 occurs, what is formed by the gamma chains of a fetus that cause damage to the RBCs?

Answer 15

Gamma tetramers—Hb barts

Question 16

What is seen on electrophoresis of a fetus that has hydrops fetalis?

Answer 16

Hb Barts

Question 17

What usually causes B-Thalassemias?

Answer 17

Gene mutations

Question 18

What chromosome are 2 beta genes present?

Answer 18

11

Question 19

What are the two results that can occur to a gene mutation to the Beta gene?

Answer 19

Absent (BO) or diminished (B+) production of the B-globin chain

Question 20

Which B-thalassemia is minor and is usually asymptomatic with an increased RBC count?

Answer 20

B/B+

Question 21

What are seen on a blood smear of a patient with B-thalassemia minor (B/B+)?

Answer 21

Microcytic, hypochromic RBCs and Target cells

Question 22

Hemoglobin electrophoresis performed on a patient with B-thalassemia minor (B/B+) will show what with respect to HbA and HbA2?

Answer 22

HbA→ slightly decreased

HbA2→ increased

Question 23

B-thalassemia major (B0/B0) will present with what?

Answer 23

Severe anemia just a few months after birth

Question 24

What is protective at birth for a patient that has B-thalassemia major (B0/B0)?

Answer 24

HbF (a2, g2)

Question 25

What are the 2 major consquences of B-Thalassemia major (B0/B0)/unpaired alpha chains?

Answer 25

Alpha chains precipitate and damage RBC membrane leading to—

1) Ineffective erythropoiesis
2) Extravascular hemolysis

Question 26

Massive erythroid hyperplasia is seen with B-Thalassemia major (B0/B0). What are the 3 things that result from this hyperplasia?

Answer 26

1) Expansion of hematopoiesis into the skull and facial bones
2) Extramedullary hematopoiesis with hepatosplenomegaly
3) Risk of aplastic criss with parvovirus B19 infection of erythroid precursors

Question 27

Expansion of hematopoiesis into the skull seen in B-Thalassemia major (B0/B0) causes what type of appearance seen on XRay?

Answer 27

Crewcut appearance due to reactive bone formation

Question 28

Chipmunk facies is seen with B-Thalassemia major (B0/B0), what is the cause of this abnormality?

Answer 28

Expansion hematopoiesis into the facial bone

Question 29

What pathogen causes aplastic crisis seen with B-Thalassemia major (B0/B0)?

Answer 29

Parvovirus B19

Question 30

Chronic transfusions are often needed for patients with B-Thalassemia major (B0/B0). This can increase the risk of developing ________.

Answer 30

Secondary hemochromatosis

Question 31

What is seen on electrophoresis in patients with B-Thalassemia major (B0/B0), with respect to HbA2, HbF and HbA?

Answer 31

HbA2 and HbF are both present

Little or NO HbA