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Terms in this set (40)
What is normal hemoglobin A composed of?
One pair of alpha chains and one pair of beta chains (alpha2/beta2)
Are beta chains soluble or insoluble?
What type of chains are insoluble?
In general, what causes thalassemias?
Reduced or absent production of one of the globin chains
In a newborn with alpha thalassemia, what type of chains are in excess?
In an adult with alpha thalassemia, what type of chains are in excess?
What can happen when excess beta chains are present in a cell?
They can form a soluble compound which is unstable and can precipitate within the cell
What is the symbol for two normal copies of the allele that codes for alpha chains?
How many normal copies of the alpha coding allele are present in a person with Thalassemia minima (or Silent Carrier, or Alpha Thalassemia Trait)?
Three normal, one abnormal (aa/a-)
How does a pt with Thalassemia minima (or Silent Carrier, or Alpha Thalassemia Trait) present?
Clinically and hematologically normal
How many normal copies of the alpha coding allele are present in a person with Alpha Thalassemia MINOR?
Two normal, two abnormal (a-/a-) or (aa/--)
How does a pt with Alpha Thalassemia MINOR present?
Clinically normal but may have mild microcytic anemia
How many normal copies of the alpha coding allele are present in a person with Alpha Thalassemia Intermedia/HbH disease have?
Only one normal, three abnormal (a-/--)
Why is Alpha Thalassemia Intermedia also called HbH disease?
HbH is formed as a result of excess beta chains
How is HbH formed?
4 unpaired beta chains bind together
What s/sx are common for someone with Alpha Thalassemia Intermedia/HbH disease?
Severe lifelong microcytic hemolytic anemia, ineffective erythropoiesis, splenomegaly
When does a person with Alpha Thalassemia Intermedia/HbH disease become transfusion dependent?
Later in life
When is Alpha Thalassemia Intermedia/HbH disease usually diagnosed?
At birth (will have neonatal jaundice)
Why is alpha chain production needed in utero?
It's need to make HbF (alpha2/gamma2)
How many normal copies of the alpha coding allele are present in a fetus with Hydrops Fetalis?
None (--/--) so alpha chains can't be made (and therefore HbA, F and A2 can't be made either)
What hemoglobin forms in Hydrops Fetalis?
Hb Barts (4 gamma chains)
What is Hb Barts' affinity for O2?
10x greater than HbA, but it doesn't release the O2 so it causes fetal demise in the 2nd or 3rd trimester
What will the MCV and MCHC be in a pt with alpha thalassemia?
Both low (microcytic, hypochromic)
What do target cells look like?
Dark center with a clear ring between the center and periphery
What are key lab findings in alpha thalassemia?
Iron usually increased
Elevated transferrin sat
Why does alpha thalassemia typically have a milder clinical presentation than beta thalassemia?
Toxicity of excess beta chains (alpha thalassemia) is less than toxicity of excess alpha chains (beta thalassemia)
What test needs to be done to diagnose alpha thalassemia minima?
How does alpha thalassemia minima present?
Typically asymptomatic, no anemia, no microcytosis
How does alpha thalassemia minor present?
Mild microcytic, hypochromic anemia
Hb electrophoresis for both alpha thalassemia minima and minor is normal. True or false?
How does Alpha Thalassemia Intermedia/Hb H Disease
Moderate microcytic, hypochromic anemia
What does Hb electrophoresis of HbH disease show?
What is diagnostic criteria for HbH disease?
HbH seen on Hb electrophoresis
Are pts with HbH disease transfusion dependent?
What happens to cells with HbH?
They are more insoluble and often lead to greater degrees of hemolysis
What symptoms are commonly present at birth in a pt with HbH disease?
Neonatal jaundice and anemia
HbH is easily oxidized (similar to G6PD deficiency). What things can trigger exacerbations of hemolysis in a pt with HbH disease?
Meds, infection, inflammation
What ethnic group has a high incidence of alpha thalassemias?
What types of alpha thalassemia don't need any treatment?
Minima and minor
What tx should be provided for HbH disease?
Follow blood work, support with transfusion, avoid oxidative stress, no role for bone marrow transplant
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