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33 Cards in this Set
- Front
- Back
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What affect does 2,3 BPG have on hemoglobin?
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Decreases its affinity for O2
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What subunits make up embryonic hemoglobin?
Fetal Hemoglobin? |
Embryonic: Gamma2Epsilon2
Fetal: α2γ2 |
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What subunits make up adult hemoglobin?
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α2β2 (Hb A) and α2δ2 (Hb A2)
Note: α2δ2 (Hb A2) is not physiologically important but useful in diagnosis |
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What do the superscripts o and + mean in terms of hemoglobinopathies?
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o = deletion
+ = non-deletion |
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Are deletion mutations (o) common in the α globin genes or β globin genes?
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α globin genes
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What are the 2 broad categories of hemoglobinopathies?
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1. Structural Hemoglobinopathies - qualitative defects
2. Thalessemias - Quantitative defects |
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What is a thalessemia?
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Group of related congenital, genetic diseases characterized by unbalanced expression of the alpha and beta globin subunits
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What predicts the severity of a thalessemia?
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The degree of alpha/beta chain imbalance
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What is alpha-thalessemia?
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Deficiency in the alpha globin subunit
- get excess Beta chains. Produce B4 (soluble) tetramers (Hb H) |
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How many alpha globin genes are there?
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4
2 from mom, 2 from dad |
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What are the different degrees of alpha thalessemia that can be observed?
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Normal = aa / aa
Silent Carrier = -a / aa alpha thalessemia trait = -a / -a or -- / aa Hb H Disease = -- / -a Hydrops Fetalis = -- / -- |
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Why is it crucial to understand the genotype of an alpha thalessemia even if the phenotype is benign?
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Because affects the inheritance pattern for future offspring.
-- / aa x -- / aa has 25% chance of hydrops fetalis -a / -a x -a / -a has 0% change of hydrops fetalis |
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What is a Beta Thalessemia?
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Deficiency of B chain globin subunits
- get excessive Alpha chains - produce A4 (precipitate out) |
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What are the 4 categories of B - Thalessemias?
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1. Normal: B / B
2. B Thalessemia Minor: B / B^o 3. B Thalessemia Intermedia: Bo / B+ or B+ / B+ 4. B Thalessemia Major: Bo / Bo Recall: o = deletion, + = non-deletion |
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What physical traits are observed in severe B-Thalessemia?
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1. Jaundice
2. Poor growth 3. Frontal Bossing 4. Splenomegaly Recall: Picture of kids from lecture |
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What type of RBC's do thalessemias produce on a peripheral smear?
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1. Microcytic
2. Hypochromic |
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What are the 2 possible causes of a low MCV?
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1. Iron Deficiency
2. Thalessemia |
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Does sickle cell cause microcytosis?
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NO NO NO!!
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Compare the values for the following between B Thalessemia and Iron Deficiency?
Hb A2 HB F Reticulocytes |
B Thalessemia / Iron Deficiency
Hb A2: Elevated / Decreased Hb F: Occiasionally elevated / Normal Reticulocytes: Elevated / Decreased |
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What is the easiest way to distinguish between an iron deficiency and B thalessemia?
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Look at Iron!
Give Iron! |
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A patient has the following values:
A (A2B2) = 94% (slightly low) A2 = 5% (high) F = normal What do they have? |
B-Thalessemia Minor
- Has one functioning B globin gene |
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A patient has the following values:
A (A2B2) = 0% (very low) A2 = 10% (high) F = 90% (very high) What do they have? |
B Thalessemia Major
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What is the therapy for thalessemia?
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PRBC Transfusion
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What is sickle cell disease?
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A congenital genetic chronic hemolytic disorder that is frequently interrupted by acute, life threatening events
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What are the 2 categories of sickle cell?
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1. Ba/Bs = AS
Sickle Cell Trait 2. Bs/Bs = SS Sickle Cell Disease |
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What is the genetic basis of sickle cell disease?
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A missense mutation causing a Glu --> Val substitution in the B-globin
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What causes the symptoms of sickle cells?
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In the deoxy form, hemoglobin forms polymers --> causes RBC's to sickle
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Where do sickle cells sickle?
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In the venous system because that is where they are deoxygenated
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What spleen size is seen in sickle cell?
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Very small
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What are 2 accepted treatments for chronic sickle cell condition?
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1. Inducers of fetal globin
2. Bone marrow transplantation |
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What is hydroxyurea?
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An inducer of fetal globin - Tx for chronic sickle cell
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Are there any morphological symptoms in sickle TRAIT?
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NO
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What is the 60/40 rule for sickle TRAIT?
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~60% of Hg should be A (a2b2) and 40% should be S (a2bs)
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