Thalassemia Flashcards
An anemia due to the decreased synthesis of the globin chains of hemoglobin…
Thalassemia
Carriers of inherited mutation seen in thalassemias are protected against what?
Plasmodium falciparum malaria
What are the 3 normal types of hemoglobin?
HbF (a2, g2)
HbA (a2, B2)
HbA2 (a2, d2)
a-Thalassemias are usually caused by what type of gene defect?
Gene deletion
How many alpha genes are present on chromosome 16?
4
If one alpha gene is deleted from chromosome 16, what symptoms is the patient most likely to experience?
Non
If two alpha genes are deleted from chromosome 16, what is the patient most likely to experience?
Mild anemia with an increased RBC count
What type of alpha deletion from chromosome 16 is associated with an increased risk of severe thalassemia in offspring?
Cis deletion—both deletions occur on the same chromosome
What ethic group has an increased incidence of Cis deletions of the alpha gene on chromosome 16?
Asians
What are the two deletions that cause occur when two alpha genes are deleted from chromosome 16?
Cis or Trans
What occurs in patients who have three alpha gene deletions on chromosome 16?
Severe anemia
When a patient presents with three alpha gene deletions on chromosome 16, what do the B chains form, which cause damage to the RBCs?
Tetramers (HbH)
When a patient presents with three alpha gene deletions on chromosome 16, what is seen on electrophoresis?
HbH—Beta tetramers
What is the most likely prognosis of a patient who has four alpha gene deletions on chromosome 16?
Lethal in utero—hydrops fetalis
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?
Gamma tetramers—Hb barts
What is seen on electrophoresis of a fetus that has hydrops fetalis?
Hb Barts
What usually causes B-Thalassemias?
Gene mutations
What chromosome are 2 beta genes present?
11
What are the two results that can occur to a gene mutation to the Beta gene?
Absent (BO) or diminished (B+) production of the B-globin chain
Which B-thalassemia is minor and is usually asymptomatic with an increased RBC count?
B/B+
What are seen on a blood smear of a patient with B-thalassemia minor (B/B+)?
Microcytic, hypochromic RBCs and Target cells
Hemoglobin electrophoresis performed on a patient with B-thalassemia minor (B/B+) will show what with respect to HbA and HbA2?
HbA→ slightly decreased
HbA2→ increased
B-thalassemia major (B0/B0) will present with what?
Severe anemia just a few months after birth
What is protective at birth for a patient that has B-thalassemia major (B0/B0)?
HbF (a2, g2)
What are the 2 major consquences of B-Thalassemia major (B0/B0)/unpaired alpha chains?
Alpha chains precipitate and damage RBC membrane leading to—
1) Ineffective erythropoiesis
2) Extravascular hemolysis
Massive erythroid hyperplasia is seen with B-Thalassemia major (B0/B0). What are the 3 things that result from this hyperplasia?
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
Expansion of hematopoiesis into the skull seen in B-Thalassemia major (B0/B0) causes what type of appearance seen on XRay?
Crewcut appearance due to reactive bone formation
Chipmunk facies is seen with B-Thalassemia major (B0/B0), what is the cause of this abnormality?
Expansion hematopoiesis into the facial bone
What pathogen causes aplastic crisis seen with B-Thalassemia major (B0/B0)?
Parvovirus B19
Chronic transfusions are often needed for patients with B-Thalassemia major (B0/B0). This can increase the risk of developing ________.
Secondary hemochromatosis
What is seen on electrophoresis in patients with B-Thalassemia major (B0/B0), with respect to HbA2, HbF and HbA?
HbA2 and HbF are both present
Little or NO HbA
